HA: Add coordinator to replication cluster (#1608)

.github/workflows/diff.yaml

@@ -337,7 +337,53 @@ jobs:
             # multiple paths could be defined
             build/logs
 
-  experimental_build:
+  experimental_build_ha:
+    name: "High availability build"
+    runs-on: [self-hosted, Linux, X64, Diff]
+    env:
+      THREADS: 24
+      MEMGRAPH_ENTERPRISE_LICENSE: ${{ secrets.MEMGRAPH_ENTERPRISE_LICENSE }}
+      MEMGRAPH_ORGANIZATION_NAME: ${{ secrets.MEMGRAPH_ORGANIZATION_NAME }}
+
+    steps:
+      - name: Set up repository
+        uses: actions/checkout@v3
+        with:
+          # Number of commits to fetch. `0` indicates all history for all
+          # branches and tags. (default: 1)
+          fetch-depth: 0
+
+      - name: Build release binaries
+        run: |
+          source /opt/toolchain-v4/activate
+          ./init
+          cd build
+          cmake -DCMAKE_BUILD_TYPE=Release -DMG_EXPERIMENTAL_HIGH_AVAILABILITY=ON ..
+          make -j$THREADS
+      - name: Run unit tests
+        run: |
+          source /opt/toolchain-v4/activate
+          cd build
+          ctest -R memgraph__unit --output-on-failure -j$THREADS
+      - name: Run e2e tests
+        run: |
+          cd tests
+          ./setup.sh /opt/toolchain-v4/activate
+          source ve3/bin/activate_e2e
+          cd e2e
+          ./run.sh "Coordinator"
+          ./run.sh "Client initiated failover"
+          ./run.sh "Uninitialized cluster"
+      - name: Save test data
+        uses: actions/upload-artifact@v3
+        if: always()
+        with:
+          name: "Test data"
+          path: |
+            # multiple paths could be defined
+            build/logs
+
+  experimental_build_mt:
     name: "MultiTenancy replication build"
     runs-on: [self-hosted, Linux, X64, Diff]
     env:

CMakeLists.txt

@@ -271,6 +271,17 @@ endif()
 set(libs_dir ${CMAKE_SOURCE_DIR}/libs)
 add_subdirectory(libs EXCLUDE_FROM_ALL)
 
+option(MG_EXPERIMENTAL_HIGH_AVAILABILITY "Feature flag for experimental high availability" OFF)
+
+if (NOT MG_ENTERPRISE AND MG_EXPERIMENTAL_HIGH_AVAILABILITY)
+    set(MG_EXPERIMENTAL_HIGH_AVAILABILITY OFF)
+    message(FATAL_ERROR "MG_EXPERIMENTAL_HIGH_AVAILABILITY must be used with enterpise version of the code.")
+endif ()
+
+if (MG_EXPERIMENTAL_HIGH_AVAILABILITY)
+    add_compile_definitions(MG_EXPERIMENTAL_HIGH_AVAILABILITY)
+endif ()
+
 # Optional subproject configuration -------------------------------------------
 option(TEST_COVERAGE "Generate coverage reports from running memgraph" OFF)
 option(TOOLS "Build tools binaries" ON)

src/CMakeLists.txt

@@ -22,6 +22,8 @@ add_subdirectory(dbms)
 add_subdirectory(flags)
 add_subdirectory(distributed)
 add_subdirectory(replication)
+add_subdirectory(coordination)
+add_subdirectory(replication_coordination_glue)
 
 string(TOLOWER ${CMAKE_BUILD_TYPE} lower_build_type)
 

src/auth/models.cpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Licensed as a Memgraph Enterprise file under the Memgraph Enterprise
 // License (the "License"); by using this file, you agree to be bound by the terms of the License, and you may not use
@@ -62,7 +62,8 @@ const std::vector<Permission> kPermissionsAll = {Permission::MATCH,
                                                  Permission::TRANSACTION_MANAGEMENT,
                                                  Permission::STORAGE_MODE,
                                                  Permission::MULTI_DATABASE_EDIT,
-                                                 Permission::MULTI_DATABASE_USE};
+                                                 Permission::MULTI_DATABASE_USE,
+                                                 Permission::COORDINATOR};
 
 }  // namespace
 
@@ -118,6 +119,8 @@ std::string PermissionToString(Permission permission) {
       return "MULTI_DATABASE_EDIT";
     case Permission::MULTI_DATABASE_USE:
       return "MULTI_DATABASE_USE";
+    case Permission::COORDINATOR:
+      return "COORDINATOR";
   }
 }
 

src/auth/models.hpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Licensed as a Memgraph Enterprise file under the Memgraph Enterprise
 // License (the "License"); by using this file, you agree to be bound by the terms of the License, and you may not use
@@ -48,6 +48,7 @@ enum class Permission : uint64_t {
   STORAGE_MODE = 1U << 22U,
   MULTI_DATABASE_EDIT = 1U << 23U,
   MULTI_DATABASE_USE  = 1U << 24U,
+  COORDINATOR  = 1U << 25U,
 };
 // clang-format on
 

src/coordination/CMakeLists.txt

@@ -0,0 +1,25 @@
+add_library(mg-coordination STATIC)
+add_library(mg::coordination ALIAS mg-coordination)
+target_sources(mg-coordination
+        PUBLIC
+        include/coordination/coordinator_client.hpp
+        include/coordination/coordinator_state.hpp
+        include/coordination/coordinator_rpc.hpp
+        include/coordination/coordinator_server.hpp
+        include/coordination/coordinator_config.hpp
+        include/coordination/coordinator_entity_info.hpp
+        include/coordination/coordinator_exceptions.hpp
+        include/coordination/coordinator_slk.hpp
+        include/coordination/constants.hpp
+
+        PRIVATE
+        coordinator_client.cpp
+        coordinator_state.cpp
+        coordinator_rpc.cpp
+        coordinator_server.cpp
+)
+target_include_directories(mg-coordination PUBLIC include)
+
+target_link_libraries(mg-coordination
+    PUBLIC mg::utils mg::rpc mg::slk mg::io mg::repl_coord_glue
+)

src/coordination/coordinator_client.cpp

@@ -0,0 +1,113 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#ifdef MG_ENTERPRISE
+
+#include "coordination/coordinator_client.hpp"
+
+#include "coordination/coordinator_config.hpp"
+#include "coordination/coordinator_rpc.hpp"
+#include "replication_coordination_glue/messages.hpp"
+
+namespace memgraph::coordination {
+
+namespace {
+auto CreateClientContext(const memgraph::coordination::CoordinatorClientConfig &config)
+    -> communication::ClientContext {
+  return (config.ssl) ? communication::ClientContext{config.ssl->key_file, config.ssl->cert_file}
+                      : communication::ClientContext{};
+}
+}  // namespace
+
+CoordinatorClient::CoordinatorClient(const CoordinatorClientConfig &config)
+    : rpc_context_{CreateClientContext(config)},
+      rpc_client_{io::network::Endpoint(io::network::Endpoint::needs_resolving, config.ip_address, config.port),
+                  &rpc_context_},
+      config_{config} {}
+
+CoordinatorClient::~CoordinatorClient() {
+  auto exit_job = utils::OnScopeExit([&] {
+    StopFrequentCheck();
+    thread_pool_.Shutdown();
+  });
+  const auto endpoint = rpc_client_.Endpoint();
+  // Logging can throw
+  spdlog::trace("Closing replication client on {}:{}", endpoint.address, endpoint.port);
+}
+
+void CoordinatorClient::StartFrequentCheck() {
+  MG_ASSERT(config_.health_check_frequency_sec > std::chrono::seconds(0),
+            "Health check frequency must be greater than 0");
+  replica_checker_.Run(
+      "Coord checker", config_.health_check_frequency_sec,
+      [last_response_time = &last_response_time_, rpc_client = &rpc_client_] {
+        try {
+          {
+            auto stream{rpc_client->Stream<memgraph::replication_coordination_glue::FrequentHeartbeatRpc>()};
+            stream.AwaitResponse();
+            last_response_time->store(std::chrono::system_clock::now(), std::memory_order_acq_rel);
+          }
+        } catch (const rpc::RpcFailedException &) {
+          // Nothing to do...wait for a reconnect
+        }
+      });
+}
+
+void CoordinatorClient::StopFrequentCheck() { replica_checker_.Stop(); }
+
+bool CoordinatorClient::DoHealthCheck() const {
+  auto current_time = std::chrono::system_clock::now();
+  auto duration = std::chrono::duration_cast<std::chrono::seconds>(current_time -
+                                                                   last_response_time_.load(std::memory_order_acquire));
+  return duration.count() <= alive_response_time_difference_sec_;
+}
+
+auto CoordinatorClient::InstanceName() const -> std::string_view { return config_.instance_name; }
+auto CoordinatorClient::Endpoint() const -> io::network::Endpoint const & { return rpc_client_.Endpoint(); }
+auto CoordinatorClient::Config() const -> CoordinatorClientConfig const & { return config_; }
+
+auto CoordinatorClient::ReplicationClientInfo() const -> CoordinatorClientConfig::ReplicationClientInfo const & {
+  MG_ASSERT(config_.replication_client_info.has_value(), "No ReplicationClientInfo for MAIN instance!");
+  return *config_.replication_client_info;
+}
+
+////// AF design choice
+auto CoordinatorClient::ReplicationClientInfo() -> std::optional<CoordinatorClientConfig::ReplicationClientInfo> & {
+  MG_ASSERT(config_.replication_client_info.has_value(), "No ReplicationClientInfo for MAIN instance!");
+  return config_.replication_client_info;
+}
+
+void CoordinatorClient::UpdateTimeCheck(const std::chrono::system_clock::time_point &last_checked_time) {
+  last_response_time_.store(last_checked_time, std::memory_order_acq_rel);
+}
+
+auto CoordinatorClient::GetLastTimeResponse() -> std::chrono::system_clock::time_point { return last_response_time_; }
+
+auto CoordinatorClient::SendPromoteReplicaToMainRpc(
+    std::vector<CoordinatorClientConfig::ReplicationClientInfo> replication_clients_info) const -> bool {
+  try {
+    {
+      auto stream{rpc_client_.Stream<PromoteReplicaToMainRpc>(std::move(replication_clients_info))};
+      if (!stream.AwaitResponse().success) {
+        spdlog::error("Failed to perform failover!");
+        return false;
+      }
+      spdlog::info("Sent failover RPC from coordinator to new main!");
+      return true;
+    }
+  } catch (const rpc::RpcFailedException &) {
+    spdlog::error("Failed to send failover RPC from coordinator to new main!");
+  }
+  return false;
+}
+
+}  // namespace memgraph::coordination
+#endif

src/coordination/coordinator_rpc.cpp

@@ -0,0 +1,69 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#ifdef MG_ENTERPRISE
+
+#include "coordination/coordinator_rpc.hpp"
+
+#include "coordination/coordinator_slk.hpp"
+#include "slk/serialization.hpp"
+
+namespace memgraph {
+
+namespace coordination {
+
+void PromoteReplicaToMainReq::Save(const PromoteReplicaToMainReq &self, memgraph::slk::Builder *builder) {
+  memgraph::slk::Save(self, builder);
+}
+
+void PromoteReplicaToMainReq::Load(PromoteReplicaToMainReq *self, memgraph::slk::Reader *reader) {
+  memgraph::slk::Load(self, reader);
+}
+
+void PromoteReplicaToMainRes::Save(const PromoteReplicaToMainRes &self, memgraph::slk::Builder *builder) {
+  memgraph::slk::Save(self, builder);
+}
+
+void PromoteReplicaToMainRes::Load(PromoteReplicaToMainRes *self, memgraph::slk::Reader *reader) {
+  memgraph::slk::Load(self, reader);
+}
+
+}  // namespace coordination
+
+constexpr utils::TypeInfo coordination::PromoteReplicaToMainReq::kType{utils::TypeId::COORD_FAILOVER_REQ,
+                                                                       "CoordPromoteReplicaToMainReq", nullptr};
+
+constexpr utils::TypeInfo coordination::PromoteReplicaToMainRes::kType{utils::TypeId::COORD_FAILOVER_RES,
+                                                                       "CoordPromoteReplicaToMainRes", nullptr};
+
+namespace slk {
+
+void Save(const memgraph::coordination::PromoteReplicaToMainRes &self, memgraph::slk::Builder *builder) {
+  memgraph::slk::Save(self.success, builder);
+}
+
+void Load(memgraph::coordination::PromoteReplicaToMainRes *self, memgraph::slk::Reader *reader) {
+  memgraph::slk::Load(&self->success, reader);
+}
+
+void Save(const memgraph::coordination::PromoteReplicaToMainReq &self, memgraph::slk::Builder *builder) {
+  memgraph::slk::Save(self.replication_clients_info, builder);
+}
+
+void Load(memgraph::coordination::PromoteReplicaToMainReq *self, memgraph::slk::Reader *reader) {
+  memgraph::slk::Load(&self->replication_clients_info, reader);
+}
+
+}  // namespace slk
+
+}  // namespace memgraph
+
+#endif

src/coordination/coordinator_server.cpp

@@ -0,0 +1,57 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#ifdef MG_ENTERPRISE
+
+#include "coordination/coordinator_server.hpp"
+#include "replication_coordination_glue/messages.hpp"
+
+namespace memgraph::coordination {
+
+namespace {
+
+auto CreateServerContext(const memgraph::coordination::CoordinatorServerConfig &config)
+    -> communication::ServerContext {
+  return (config.ssl) ? communication::ServerContext{config.ssl->key_file, config.ssl->cert_file, config.ssl->ca_file,
+                                                     config.ssl->verify_peer}
+                      : communication::ServerContext{};
+}
+
+// NOTE: The coordinator server doesn't more than 1 processing thread - each replica can
+// have only a single coordinator server. Also, the single-threaded guarantee
+// simplifies the rest of the implementation.
+constexpr auto kCoordinatorServerThreads = 1;
+
+}  // namespace
+
+CoordinatorServer::CoordinatorServer(const CoordinatorServerConfig &config)
+    : rpc_server_context_{CreateServerContext(config)},
+      rpc_server_{io::network::Endpoint{config.ip_address, config.port}, &rpc_server_context_,
+                  kCoordinatorServerThreads} {
+  rpc_server_.Register<replication_coordination_glue::FrequentHeartbeatRpc>([](auto *req_reader, auto *res_builder) {
+    spdlog::debug("Received FrequentHeartbeatRpc on coordinator server");
+    replication_coordination_glue::FrequentHeartbeatHandler(req_reader, res_builder);
+  });
+}
+
+CoordinatorServer::~CoordinatorServer() {
+  if (rpc_server_.IsRunning()) {
+    auto const &endpoint = rpc_server_.endpoint();
+    spdlog::trace("Closing coordinator server on {}:{}", endpoint.address, endpoint.port);
+    rpc_server_.Shutdown();
+  }
+  rpc_server_.AwaitShutdown();
+}
+
+bool CoordinatorServer::Start() { return rpc_server_.Start(); }
+
+}  // namespace memgraph::coordination
+#endif

src/coordination/coordinator_state.cpp

@@ -0,0 +1,221 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#include "coordination/coordinator_state.hpp"
+#include <span>
+#include "coordination/coordinator_client.hpp"
+
+#ifdef MG_ENTERPRISE
+
+#include "coordination/coordinator_config.hpp"
+#include "coordination/coordinator_entity_info.hpp"
+#include "flags/replication.hpp"
+#include "spdlog/spdlog.h"
+#include "utils/logging.hpp"
+#include "utils/variant_helpers.hpp"
+
+#include <atomic>
+#include <exception>
+#include <optional>
+
+namespace memgraph::coordination {
+
+namespace {
+
+bool CheckName(const std::list<CoordinatorClient> &replicas, const CoordinatorClientConfig &config) {
+  auto name_matches = [&instance_name = config.instance_name](auto const &replica) {
+    return replica.InstanceName() == instance_name;
+  };
+  return std::any_of(replicas.begin(), replicas.end(), name_matches);
+};
+
+}  // namespace
+
+CoordinatorState::CoordinatorState() {
+  MG_ASSERT(!(FLAGS_coordinator && FLAGS_coordinator_server_port),
+            "Instance cannot be a coordinator and have registered coordinator server.");
+
+  if (FLAGS_coordinator_server_port) {
+    auto const config = CoordinatorServerConfig{
+        .ip_address = kDefaultReplicationServerIp,
+        .port = static_cast<uint16_t>(FLAGS_coordinator_server_port),
+    };
+
+    data_ = CoordinatorMainReplicaData{.coordinator_server_ = std::make_unique<CoordinatorServer>(config)};
+  }
+}
+
+auto CoordinatorState::RegisterReplica(const CoordinatorClientConfig &config)
+    -> utils::BasicResult<RegisterMainReplicaCoordinatorStatus, CoordinatorClient *> {
+  const auto name_endpoint_status =
+      std::visit(memgraph::utils::Overloaded{[](const CoordinatorMainReplicaData & /*coordinator_main_replica_data*/) {
+                                               return RegisterMainReplicaCoordinatorStatus::NOT_COORDINATOR;
+                                             },
+                                             [&config](const CoordinatorData &coordinator_data) {
+                                               if (memgraph::coordination::CheckName(
+                                                       coordinator_data.registered_replicas_, config)) {
+                                                 return RegisterMainReplicaCoordinatorStatus::NAME_EXISTS;
+                                               }
+                                               return RegisterMainReplicaCoordinatorStatus::SUCCESS;
+                                             }},
+                 data_);
+
+  if (name_endpoint_status != RegisterMainReplicaCoordinatorStatus::SUCCESS) {
+    return name_endpoint_status;
+  }
+
+  // Maybe no need to return client if you can start replica client here
+  return &std::get<CoordinatorData>(data_).registered_replicas_.emplace_back(config);
+}
+
+auto CoordinatorState::RegisterMain(const CoordinatorClientConfig &config)
+    -> utils::BasicResult<RegisterMainReplicaCoordinatorStatus, CoordinatorClient *> {
+  const auto endpoint_status = std::visit(
+      memgraph::utils::Overloaded{
+          [](const CoordinatorMainReplicaData & /*coordinator_main_replica_data*/) {
+            return RegisterMainReplicaCoordinatorStatus::NOT_COORDINATOR;
+          },
+          [](const CoordinatorData & /*coordinator_data*/) { return RegisterMainReplicaCoordinatorStatus::SUCCESS; }},
+      data_);
+
+  if (endpoint_status != RegisterMainReplicaCoordinatorStatus::SUCCESS) {
+    return endpoint_status;
+  }
+
+  auto &registered_main = std::get<CoordinatorData>(data_).registered_main_;
+  registered_main = std::make_unique<CoordinatorClient>(config);
+  return registered_main.get();
+}
+
+auto CoordinatorState::ShowReplicas() const -> std::vector<CoordinatorEntityInfo> {
+  MG_ASSERT(std::holds_alternative<CoordinatorData>(data_),
+            "Can't call show replicas on data_, as variant holds wrong alternative");
+  std::vector<CoordinatorEntityInfo> result;
+  const auto &registered_replicas = std::get<CoordinatorData>(data_).registered_replicas_;
+  result.reserve(registered_replicas.size());
+  std::ranges::transform(registered_replicas, std::back_inserter(result), [](const auto &replica) {
+    return CoordinatorEntityInfo{replica.InstanceName(), replica.Endpoint()};
+  });
+  return result;
+}
+
+auto CoordinatorState::ShowMain() const -> std::optional<CoordinatorEntityInfo> {
+  MG_ASSERT(std::holds_alternative<CoordinatorData>(data_),
+            "Can't call show main on data_, as variant holds wrong alternative");
+  const auto &registered_main = std::get<CoordinatorData>(data_).registered_main_;
+  if (registered_main) {
+    return CoordinatorEntityInfo{registered_main->InstanceName(), registered_main->Endpoint()};
+  }
+  return std::nullopt;
+}
+
+auto CoordinatorState::PingReplicas() const -> std::unordered_map<std::string_view, bool> {
+  MG_ASSERT(std::holds_alternative<CoordinatorData>(data_),
+            "Can't call ping replicas on data_, as variant holds wrong alternative");
+  std::unordered_map<std::string_view, bool> result;
+  const auto &registered_replicas = std::get<CoordinatorData>(data_).registered_replicas_;
+  result.reserve(registered_replicas.size());
+  for (const CoordinatorClient &replica_client : registered_replicas) {
+    result.emplace(replica_client.InstanceName(), replica_client.DoHealthCheck());
+  }
+
+  return result;
+}
+
+auto CoordinatorState::PingMain() const -> std::optional<CoordinatorEntityHealthInfo> {
+  MG_ASSERT(std::holds_alternative<CoordinatorData>(data_),
+            "Can't call show main on data_, as variant holds wrong alternative");
+  const auto &registered_main = std::get<CoordinatorData>(data_).registered_main_;
+  if (registered_main) {
+    return CoordinatorEntityHealthInfo{registered_main->InstanceName(), registered_main->DoHealthCheck()};
+  }
+  return std::nullopt;
+}
+
+auto CoordinatorState::DoFailover() -> DoFailoverStatus {
+  // 1. MAIN is already down, stop sending frequent checks
+  // 2. find new replica (coordinator)
+  // 3. make copy replica's client as potential new main client (coordinator)
+  // 4. send failover RPC to new main (coordinator and new main)
+  // 5. exchange old main to new main (coordinator)
+  // 6. remove replica which was promoted to main from all replicas -> this will shut down RPC frequent check client
+  // (coordinator)
+  // 7. for new main start frequent checks (coordinator)
+
+  MG_ASSERT(std::holds_alternative<CoordinatorData>(data_), "Cannot do failover since variant holds wrong alternative");
+  using ReplicationClientInfo = CoordinatorClientConfig::ReplicationClientInfo;
+
+  // 1.
+  auto &current_main = std::get<CoordinatorData>(data_).registered_main_;
+
+  if (!current_main) {
+    return DoFailoverStatus::CLUSTER_UNINITIALIZED;
+  }
+
+  if (current_main->DoHealthCheck()) {
+    return DoFailoverStatus::MAIN_ALIVE;
+  }
+  current_main->StopFrequentCheck();
+
+  // 2.
+  // Get all replicas and find new main
+  auto &registered_replicas = std::get<CoordinatorData>(data_).registered_replicas_;
+
+  const auto chosen_replica = std::ranges::find_if(
+      registered_replicas, [](const CoordinatorClient &replica) { return replica.DoHealthCheck(); });
+  if (chosen_replica == registered_replicas.end()) {
+    return DoFailoverStatus::ALL_REPLICAS_DOWN;
+  }
+
+  std::vector<ReplicationClientInfo> repl_clients_info;
+  repl_clients_info.reserve(registered_replicas.size() - 1);
+  std::ranges::for_each(registered_replicas, [&chosen_replica, &repl_clients_info](const CoordinatorClient &replica) {
+    if (replica != *chosen_replica) {
+      repl_clients_info.emplace_back(replica.ReplicationClientInfo());
+    }
+  });
+
+  // 3.
+  // Set on coordinator data of new main
+  // allocate resources for new main, clear replication info on this replica as main
+  // set last response time
+  auto potential_new_main = std::make_unique<CoordinatorClient>(chosen_replica->Config());
+  potential_new_main->ReplicationClientInfo().reset();
+  potential_new_main->UpdateTimeCheck(chosen_replica->GetLastTimeResponse());
+
+  // 4.
+  if (!chosen_replica->SendPromoteReplicaToMainRpc(std::move(repl_clients_info))) {
+    spdlog::error("Sent RPC message, but exception was caught, aborting Failover");
+    // TODO: new status and rollback all changes that were done...
+    MG_ASSERT(false, "RPC message failed");
+  }
+
+  // 5.
+  current_main = std::move(potential_new_main);
+
+  // 6. remove old replica
+  // TODO: Stop pinging chosen_replica before failover.
+  // Check that it doesn't fail when you call StopFrequentCheck if it is already stopped
+  registered_replicas.erase(chosen_replica);
+
+  // 7.
+  current_main->StartFrequentCheck();
+
+  return DoFailoverStatus::SUCCESS;
+}
+
+auto CoordinatorState::GetCoordinatorServer() const -> CoordinatorServer & {
+  MG_ASSERT(std::holds_alternative<CoordinatorMainReplicaData>(data_),
+            "Cannot get coordinator server since variant holds wrong alternative");
+  return *std::get<CoordinatorMainReplicaData>(data_).coordinator_server_;
+}
+}  // namespace memgraph::coordination
+#endif

src/coordination/include/coordination/constants.hpp

@@ -0,0 +1,22 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+namespace memgraph::coordination {
+
+#ifdef MG_EXPERIMENTAL_HIGH_AVAILABILITY
+constexpr bool allow_ha = true;
+#else
+constexpr bool allow_ha = false;
+#endif
+
+}  // namespace memgraph::coordination

src/coordination/include/coordination/coordinator_client.hpp

@@ -0,0 +1,69 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#ifdef MG_ENTERPRISE
+
+#include "coordination/coordinator_config.hpp"
+#include "rpc/client.hpp"
+#include "utils/scheduler.hpp"
+#include "utils/thread_pool.hpp"
+
+#include <string_view>
+
+namespace memgraph::coordination {
+
+class CoordinatorClient {
+ public:
+  explicit CoordinatorClient(const CoordinatorClientConfig &config);
+
+  ~CoordinatorClient();
+
+  CoordinatorClient(CoordinatorClient &other) = delete;
+  CoordinatorClient &operator=(CoordinatorClient const &other) = delete;
+
+  CoordinatorClient(CoordinatorClient &&) noexcept = delete;
+  CoordinatorClient &operator=(CoordinatorClient &&) noexcept = delete;
+
+  void StartFrequentCheck();
+  void StopFrequentCheck();
+
+  auto DoHealthCheck() const -> bool;
+  auto SendPromoteReplicaToMainRpc(
+      std::vector<CoordinatorClientConfig::ReplicationClientInfo> replication_clients_info) const -> bool;
+
+  auto InstanceName() const -> std::string_view;
+  auto Endpoint() const -> io::network::Endpoint const &;
+  auto Config() const -> CoordinatorClientConfig const &;
+  auto ReplicationClientInfo() const -> CoordinatorClientConfig::ReplicationClientInfo const &;
+  auto ReplicationClientInfo() -> std::optional<CoordinatorClientConfig::ReplicationClientInfo> &;
+  void UpdateTimeCheck(const std::chrono::system_clock::time_point &last_checked_time);
+  auto GetLastTimeResponse() -> std::chrono::system_clock::time_point;
+
+  friend bool operator==(CoordinatorClient const &first, CoordinatorClient const &second) {
+    return first.config_ == second.config_;
+  }
+
+ private:
+  utils::ThreadPool thread_pool_{1};
+  utils::Scheduler replica_checker_;
+
+  communication::ClientContext rpc_context_;
+  mutable rpc::Client rpc_client_;
+  CoordinatorClientConfig config_;
+
+  std::atomic<std::chrono::system_clock::time_point> last_response_time_{};
+  static constexpr int alive_response_time_difference_sec_{5};
+};
+
+}  // namespace memgraph::coordination
+#endif

src/coordination/include/coordination/coordinator_config.hpp

@@ -0,0 +1,77 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#ifdef MG_ENTERPRISE
+
+#include "replication_coordination_glue/mode.hpp"
+
+#include <chrono>
+#include <cstdint>
+#include <optional>
+#include <string>
+
+namespace memgraph::coordination {
+
+inline constexpr auto *kDefaultReplicationServerIp = "0.0.0.0";
+
+struct CoordinatorClientConfig {
+  const std::string instance_name;
+  const std::string ip_address;
+  const uint16_t port{};
+
+  // Frequency with which coordinator pings main/replicas about it status
+  const std::chrono::seconds health_check_frequency_sec{1};
+
+  // Info which coordinator will send to new main when performing failover
+  struct ReplicationClientInfo {
+    // Should be the same as CoordinatorClientConfig's instance_name
+    std::string instance_name;
+    replication_coordination_glue::ReplicationMode replication_mode{};
+    std::string replication_ip_address;
+    uint16_t replication_port{};
+
+    friend bool operator==(ReplicationClientInfo const &, ReplicationClientInfo const &) = default;
+  };
+
+  std::optional<ReplicationClientInfo> replication_client_info;
+
+  struct SSL {
+    const std::string key_file;
+    const std::string cert_file;
+
+    friend bool operator==(const SSL &, const SSL &) = default;
+  };
+
+  const std::optional<SSL> ssl;
+
+  friend bool operator==(CoordinatorClientConfig const &, CoordinatorClientConfig const &) = default;
+};
+
+struct CoordinatorServerConfig {
+  std::string ip_address;
+  uint16_t port{};
+  struct SSL {
+    std::string key_file;
+    std::string cert_file;
+    std::string ca_file;
+    bool verify_peer{};
+    friend bool operator==(SSL const &, SSL const &) = default;
+  };
+
+  std::optional<SSL> ssl;
+
+  friend bool operator==(CoordinatorServerConfig const &, CoordinatorServerConfig const &) = default;
+};
+
+}  // namespace memgraph::coordination
+#endif

src/coordination/include/coordination/coordinator_entity_info.hpp

@@ -0,0 +1,34 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#ifdef MG_ENTERPRISE
+
+#include "io/network/endpoint.hpp"
+
+#include <string>
+
+namespace memgraph::coordination {
+
+struct CoordinatorEntityInfo {
+  std::string_view name;
+  const io::network::Endpoint &endpoint;
+};
+
+struct CoordinatorEntityHealthInfo {
+  std::string_view name;
+  bool alive;
+};
+
+}  // namespace memgraph::coordination
+
+#endif

src/coordination/include/coordination/coordinator_exceptions.hpp

@@ -0,0 +1,32 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#ifdef MG_ENTERPRISE
+
+#include "utils/exceptions.hpp"
+
+namespace memgraph::coordination {
+class CoordinatorFailoverException final : public utils::BasicException {
+ public:
+  explicit CoordinatorFailoverException(const std::string_view what) noexcept
+      : BasicException("Failover didn't complete successfully: " + std::string(what)) {}
+
+  template <class... Args>
+  explicit CoordinatorFailoverException(fmt::format_string<Args...> fmt, Args &&...args) noexcept
+      : CoordinatorFailoverException(fmt::format(fmt, std::forward<Args>(args)...)) {}
+
+  SPECIALIZE_GET_EXCEPTION_NAME(CoordinatorFailoverException)
+};
+
+}  // namespace memgraph::coordination
+#endif

src/coordination/include/coordination/coordinator_rpc.hpp

@@ -0,0 +1,66 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#ifdef MG_ENTERPRISE
+
+#include "coordination/coordinator_config.hpp"
+#include "rpc/messages.hpp"
+#include "slk/serialization.hpp"
+
+namespace memgraph::coordination {
+
+struct PromoteReplicaToMainReq {
+  static const utils::TypeInfo kType;
+  static const utils::TypeInfo &GetTypeInfo() { return kType; }
+
+  static void Load(PromoteReplicaToMainReq *self, memgraph::slk::Reader *reader);
+  static void Save(const PromoteReplicaToMainReq &self, memgraph::slk::Builder *builder);
+
+  explicit PromoteReplicaToMainReq(std::vector<CoordinatorClientConfig::ReplicationClientInfo> replication_clients_info)
+      : replication_clients_info(std::move(replication_clients_info)) {}
+  PromoteReplicaToMainReq() = default;
+
+  std::vector<CoordinatorClientConfig::ReplicationClientInfo> replication_clients_info;
+};
+
+struct PromoteReplicaToMainRes {
+  static const utils::TypeInfo kType;
+  static const utils::TypeInfo &GetTypeInfo() { return kType; }
+
+  static void Load(PromoteReplicaToMainRes *self, memgraph::slk::Reader *reader);
+  static void Save(const PromoteReplicaToMainRes &self, memgraph::slk::Builder *builder);
+
+  explicit PromoteReplicaToMainRes(bool success) : success(success) {}
+  PromoteReplicaToMainRes() = default;
+
+  bool success;
+};
+
+using PromoteReplicaToMainRpc = rpc::RequestResponse<PromoteReplicaToMainReq, PromoteReplicaToMainRes>;
+
+}  // namespace memgraph::coordination
+
+// SLK serialization declarations
+namespace memgraph::slk {
+
+void Save(const memgraph::coordination::PromoteReplicaToMainRes &self, memgraph::slk::Builder *builder);
+
+void Load(memgraph::coordination::PromoteReplicaToMainRes *self, memgraph::slk::Reader *reader);
+
+void Save(const memgraph::coordination::PromoteReplicaToMainReq &self, memgraph::slk::Builder *builder);
+
+void Load(memgraph::coordination::PromoteReplicaToMainReq *self, memgraph::slk::Reader *reader);
+
+}  // namespace memgraph::slk
+
+#endif

src/coordination/include/coordination/coordinator_server.hpp

@@ -0,0 +1,44 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#ifdef MG_ENTERPRISE
+
+#include "coordination/coordinator_config.hpp"
+#include "rpc/server.hpp"
+
+namespace memgraph::coordination {
+
+class CoordinatorServer {
+ public:
+  explicit CoordinatorServer(const CoordinatorServerConfig &config);
+  CoordinatorServer(const CoordinatorServer &) = delete;
+  CoordinatorServer(CoordinatorServer &&) = delete;
+  CoordinatorServer &operator=(const CoordinatorServer &) = delete;
+  CoordinatorServer &operator=(CoordinatorServer &&) = delete;
+
+  virtual ~CoordinatorServer();
+
+  bool Start();
+
+  template <typename TRequestResponse, typename F>
+  void Register(F &&callback) {
+    rpc_server_.Register<TRequestResponse>(std::forward<F>(callback));
+  }
+
+ private:
+  communication::ServerContext rpc_server_context_;
+  rpc::Server rpc_server_;
+};
+
+}  // namespace memgraph::coordination
+#endif

src/coordination/include/coordination/coordinator_slk.hpp

@@ -0,0 +1,38 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#ifdef MG_ENTERPRISE
+
+#include "coordination/coordinator_config.hpp"
+#include "slk/serialization.hpp"
+#include "slk/streams.hpp"
+
+namespace memgraph::slk {
+
+using ReplicationClientInfo = coordination::CoordinatorClientConfig::ReplicationClientInfo;
+
+inline void Save(const ReplicationClientInfo &obj, Builder *builder) {
+  Save(obj.instance_name, builder);
+  Save(obj.replication_mode, builder);
+  Save(obj.replication_ip_address, builder);
+  Save(obj.replication_port, builder);
+}
+
+inline void Load(ReplicationClientInfo *obj, Reader *reader) {
+  Load(&obj->instance_name, reader);
+  Load(&obj->replication_mode, reader);
+  Load(&obj->replication_ip_address, reader);
+  Load(&obj->replication_port, reader);
+}
+}  // namespace memgraph::slk
+#endif

src/coordination/include/coordination/coordinator_state.hpp

@@ -0,0 +1,94 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#ifdef MG_ENTERPRISE
+
+#include "coordination/coordinator_client.hpp"
+#include "coordination/coordinator_entity_info.hpp"
+#include "coordination/coordinator_server.hpp"
+#include "rpc/server.hpp"
+#include "utils/result.hpp"
+#include "utils/rw_spin_lock.hpp"
+#include "utils/synchronized.hpp"
+
+#include <list>
+#include <variant>
+
+namespace memgraph::coordination {
+
+enum class RegisterMainReplicaCoordinatorStatus : uint8_t {
+  NAME_EXISTS,
+  END_POINT_EXISTS,
+  COULD_NOT_BE_PERSISTED,
+  NOT_COORDINATOR,
+  SUCCESS
+};
+
+enum class DoFailoverStatus : uint8_t { SUCCESS, ALL_REPLICAS_DOWN, MAIN_ALIVE, CLUSTER_UNINITIALIZED };
+
+class CoordinatorState {
+ public:
+  CoordinatorState();
+  ~CoordinatorState() = default;
+
+  CoordinatorState(const CoordinatorState &) = delete;
+  CoordinatorState &operator=(const CoordinatorState &) = delete;
+
+  CoordinatorState(CoordinatorState &&other) noexcept : data_(std::move(other.data_)) {}
+
+  CoordinatorState &operator=(CoordinatorState &&other) noexcept {
+    if (this == &other) {
+      return *this;
+    }
+    data_ = std::move(other.data_);
+    return *this;
+  }
+
+  auto RegisterReplica(const CoordinatorClientConfig &config)
+      -> utils::BasicResult<RegisterMainReplicaCoordinatorStatus, CoordinatorClient *>;
+
+  auto RegisterMain(const CoordinatorClientConfig &config)
+      -> utils::BasicResult<RegisterMainReplicaCoordinatorStatus, CoordinatorClient *>;
+
+  auto ShowReplicas() const -> std::vector<CoordinatorEntityInfo>;
+
+  auto PingReplicas() const -> std::unordered_map<std::string_view, bool>;
+
+  auto ShowMain() const -> std::optional<CoordinatorEntityInfo>;
+
+  auto PingMain() const -> std::optional<CoordinatorEntityHealthInfo>;
+
+  // The client code must check that the server exists before calling this method.
+  auto GetCoordinatorServer() const -> CoordinatorServer &;
+
+  auto DoFailover() -> DoFailoverStatus;
+
+ private:
+  // TODO: Data is not thread safe
+
+  // Coordinator stores registered replicas and main
+  struct CoordinatorData {
+    std::list<CoordinatorClient> registered_replicas_;
+    std::unique_ptr<CoordinatorClient> registered_main_;
+  };
+
+  // Data which each main and replica stores
+  struct CoordinatorMainReplicaData {
+    std::unique_ptr<CoordinatorServer> coordinator_server_;
+  };
+
+  std::variant<CoordinatorData, CoordinatorMainReplicaData> data_;
+};
+
+}  // namespace memgraph::coordination
+#endif

src/dbms/CMakeLists.txt

@@ -1,3 +1,2 @@
-
+add_library(mg-dbms STATIC dbms_handler.cpp database.cpp replication_handler.cpp coordinator_handler.cpp replication_client.cpp inmemory/replication_handlers.cpp coordinator_handlers.cpp)
-add_library(mg-dbms STATIC dbms_handler.cpp database.cpp replication_handler.cpp replication_client.cpp inmemory/replication_handlers.cpp)
+target_link_libraries(mg-dbms mg-utils mg-storage-v2 mg-query mg-replication mg-coordination)
-target_link_libraries(mg-dbms mg-utils mg-storage-v2 mg-query)

src/dbms/coordinator_handler.cpp

@@ -0,0 +1,99 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#ifdef MG_ENTERPRISE
+
+#include "dbms/coordinator_handler.hpp"
+
+#include "dbms/dbms_handler.hpp"
+
+namespace memgraph::dbms {
+
+CoordinatorHandler::CoordinatorHandler(DbmsHandler &dbms_handler) : dbms_handler_(dbms_handler) {}
+
+auto CoordinatorHandler::RegisterReplicaOnCoordinator(const memgraph::coordination::CoordinatorClientConfig &config)
+    -> utils::BasicResult<RegisterMainReplicaCoordinatorStatus> {
+  auto instance_client = dbms_handler_.CoordinatorState().RegisterReplica(config);
+  using repl_status = memgraph::coordination::RegisterMainReplicaCoordinatorStatus;
+  using dbms_status = memgraph::dbms::RegisterMainReplicaCoordinatorStatus;
+  if (instance_client.HasError()) {
+    switch (instance_client.GetError()) {
+      case memgraph::coordination::RegisterMainReplicaCoordinatorStatus::NOT_COORDINATOR:
+        MG_ASSERT(false, "Only coordinator instance can register main and replica!");
+        return {};
+      case repl_status::NAME_EXISTS:
+        return dbms_status::NAME_EXISTS;
+      case repl_status::END_POINT_EXISTS:
+        return dbms_status::END_POINT_EXISTS;
+      case repl_status::COULD_NOT_BE_PERSISTED:
+        return dbms_status::COULD_NOT_BE_PERSISTED;
+      case repl_status::SUCCESS:
+        break;
+    }
+  }
+
+  instance_client.GetValue()->StartFrequentCheck();
+  return {};
+}
+
+auto CoordinatorHandler::RegisterMainOnCoordinator(const memgraph::coordination::CoordinatorClientConfig &config)
+    -> utils::BasicResult<RegisterMainReplicaCoordinatorStatus> {
+  auto instance_client = dbms_handler_.CoordinatorState().RegisterMain(config);
+  if (instance_client.HasError()) switch (instance_client.GetError()) {
+      case memgraph::coordination::RegisterMainReplicaCoordinatorStatus::NOT_COORDINATOR:
+        MG_ASSERT(false, "Only coordinator instance can register main and replica!");
+      case memgraph::coordination::RegisterMainReplicaCoordinatorStatus::NAME_EXISTS:
+        return memgraph::dbms::RegisterMainReplicaCoordinatorStatus::NAME_EXISTS;
+      case memgraph::coordination::RegisterMainReplicaCoordinatorStatus::END_POINT_EXISTS:
+        return memgraph::dbms::RegisterMainReplicaCoordinatorStatus::END_POINT_EXISTS;
+      case memgraph::coordination::RegisterMainReplicaCoordinatorStatus::COULD_NOT_BE_PERSISTED:
+        return memgraph::dbms::RegisterMainReplicaCoordinatorStatus::COULD_NOT_BE_PERSISTED;
+      case memgraph::coordination::RegisterMainReplicaCoordinatorStatus::SUCCESS:
+        break;
+    }
+
+  instance_client.GetValue()->StartFrequentCheck();
+  return {};
+}
+
+auto CoordinatorHandler::ShowReplicasOnCoordinator() const -> std::vector<coordination::CoordinatorEntityInfo> {
+  return dbms_handler_.CoordinatorState().ShowReplicas();
+}
+
+auto CoordinatorHandler::PingReplicasOnCoordinator() const -> std::unordered_map<std::string_view, bool> {
+  return dbms_handler_.CoordinatorState().PingReplicas();
+}
+
+auto CoordinatorHandler::ShowMainOnCoordinator() const -> std::optional<coordination::CoordinatorEntityInfo> {
+  return dbms_handler_.CoordinatorState().ShowMain();
+}
+
+auto CoordinatorHandler::PingMainOnCoordinator() const -> std::optional<coordination::CoordinatorEntityHealthInfo> {
+  return dbms_handler_.CoordinatorState().PingMain();
+}
+
+auto CoordinatorHandler::DoFailover() const -> DoFailoverStatus {
+  auto status = dbms_handler_.CoordinatorState().DoFailover();
+  switch (status) {
+    case memgraph::coordination::DoFailoverStatus::ALL_REPLICAS_DOWN:
+      return memgraph::dbms::DoFailoverStatus::ALL_REPLICAS_DOWN;
+    case memgraph::coordination::DoFailoverStatus::SUCCESS:
+      return memgraph::dbms::DoFailoverStatus::SUCCESS;
+    case memgraph::coordination::DoFailoverStatus::MAIN_ALIVE:
+      return memgraph::dbms::DoFailoverStatus::MAIN_ALIVE;
+    case memgraph::coordination::DoFailoverStatus::CLUSTER_UNINITIALIZED:
+      return memgraph::dbms::DoFailoverStatus::CLUSTER_UNINITIALIZED;
+  }
+}
+
+}  // namespace memgraph::dbms
+
+#endif

src/dbms/coordinator_handler.hpp

@@ -0,0 +1,67 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#ifdef MG_ENTERPRISE
+
+#include "utils/result.hpp"
+
+#include <cstdint>
+#include <optional>
+#include <vector>
+
+namespace memgraph::coordination {
+struct CoordinatorEntityInfo;
+struct CoordinatorEntityHealthInfo;
+struct CoordinatorClientConfig;
+}  // namespace memgraph::coordination
+
+namespace memgraph::dbms {
+
+enum class RegisterMainReplicaCoordinatorStatus : uint8_t {
+  NAME_EXISTS,
+  END_POINT_EXISTS,
+  COULD_NOT_BE_PERSISTED,
+  NOT_COORDINATOR,
+  SUCCESS
+};
+
+enum class DoFailoverStatus : uint8_t { SUCCESS, ALL_REPLICAS_DOWN, MAIN_ALIVE, CLUSTER_UNINITIALIZED };
+
+class DbmsHandler;
+
+class CoordinatorHandler {
+ public:
+  explicit CoordinatorHandler(DbmsHandler &dbms_handler);
+
+  auto RegisterReplicaOnCoordinator(const memgraph::coordination::CoordinatorClientConfig &config)
+      -> utils::BasicResult<RegisterMainReplicaCoordinatorStatus>;
+
+  auto RegisterMainOnCoordinator(const memgraph::coordination::CoordinatorClientConfig &config)
+      -> utils::BasicResult<RegisterMainReplicaCoordinatorStatus>;
+
+  auto ShowReplicasOnCoordinator() const -> std::vector<memgraph::coordination::CoordinatorEntityInfo>;
+
+  auto ShowMainOnCoordinator() const -> std::optional<memgraph::coordination::CoordinatorEntityInfo>;
+
+  auto PingReplicasOnCoordinator() const -> std::unordered_map<std::string_view, bool>;
+
+  auto PingMainOnCoordinator() const -> std::optional<memgraph::coordination::CoordinatorEntityHealthInfo>;
+
+  auto DoFailover() const -> DoFailoverStatus;
+
+ private:
+  DbmsHandler &dbms_handler_;
+};
+
+}  // namespace memgraph::dbms
+#endif

src/dbms/coordinator_handlers.cpp

@@ -0,0 +1,106 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#ifdef MG_ENTERPRISE
+
+#include "dbms/coordinator_handlers.hpp"
+#include "dbms/utils.hpp"
+
+#include "coordination/coordinator_exceptions.hpp"
+#include "coordination/coordinator_rpc.hpp"
+#include "dbms/dbms_handler.hpp"
+#include "dbms/replication_client.hpp"
+
+namespace memgraph::dbms {
+
+void CoordinatorHandlers::Register(DbmsHandler &dbms_handler) {
+  auto &server = dbms_handler.CoordinatorState().GetCoordinatorServer();
+
+  server.Register<coordination::PromoteReplicaToMainRpc>(
+      [&dbms_handler](slk::Reader *req_reader, slk::Builder *res_builder) -> void {
+        spdlog::info("Received PromoteReplicaToMainRpc from coordinator server");
+        CoordinatorHandlers::PromoteReplicaToMainHandler(dbms_handler, req_reader, res_builder);
+      });
+}
+
+void CoordinatorHandlers::PromoteReplicaToMainHandler(DbmsHandler &dbms_handler, slk::Reader *req_reader,
+                                                      slk::Builder *res_builder) {
+  auto &repl_state = dbms_handler.ReplicationState();
+
+  if (!repl_state.IsReplica()) {
+    spdlog::error("Failover must be performed on replica!");
+    slk::Save(coordination::PromoteReplicaToMainRes{false}, res_builder);
+    return;
+  }
+
+  if (bool success = memgraph::dbms::DoReplicaToMainPromotion(dbms_handler); !success) {
+    spdlog::error("Promoting replica to main failed!");
+    slk::Save(coordination::PromoteReplicaToMainRes{false}, res_builder);
+    return;
+  }
+
+  coordination::PromoteReplicaToMainReq req;
+  slk::Load(&req, req_reader);
+
+  std::vector<replication::ReplicationClientConfig> clients_config;
+  clients_config.reserve(req.replication_clients_info.size());
+  std::ranges::transform(req.replication_clients_info, std::back_inserter(clients_config),
+                         [](const auto &repl_info_config) {
+                           return replication::ReplicationClientConfig{
+                               .name = repl_info_config.instance_name,
+                               .mode = repl_info_config.replication_mode,
+                               .ip_address = repl_info_config.replication_ip_address,
+                               .port = repl_info_config.replication_port,
+                           };
+                         });
+
+  std::ranges::for_each(clients_config, [&dbms_handler, &repl_state, &res_builder](const auto &config) {
+    auto instance_client = repl_state.RegisterReplica(config);
+    if (instance_client.HasError()) {
+      switch (instance_client.GetError()) {
+        case memgraph::replication::RegisterReplicaError::NOT_MAIN:
+          spdlog::error("Failover must be performed to main!");
+          slk::Save(coordination::PromoteReplicaToMainRes{false}, res_builder);
+          return;
+        case memgraph::replication::RegisterReplicaError::NAME_EXISTS:
+          spdlog::error("Replica with the same name already exists!");
+          slk::Save(coordination::PromoteReplicaToMainRes{false}, res_builder);
+          return;
+        case memgraph::replication::RegisterReplicaError::END_POINT_EXISTS:
+          spdlog::error("Replica with the same endpoint already exists!");
+          slk::Save(coordination::PromoteReplicaToMainRes{false}, res_builder);
+          return;
+        case memgraph::replication::RegisterReplicaError::COULD_NOT_BE_PERSISTED:
+          spdlog::error("Registered replica could not be persisted!");
+          slk::Save(coordination::PromoteReplicaToMainRes{false}, res_builder);
+          return;
+        case memgraph::replication::RegisterReplicaError::SUCCESS:
+          break;
+      }
+    }
+
+    auto &instance_client_ref = *instance_client.GetValue();
+    const bool all_clients_good = memgraph::dbms::RegisterAllDatabasesClients(dbms_handler, instance_client_ref);
+
+    if (!all_clients_good) {
+      spdlog::error("Failed to register all databases to the REPLICA \"{}\"", config.name);
+      slk::Save(coordination::PromoteReplicaToMainRes{false}, res_builder);
+      return;
+    }
+
+    StartReplicaClient(dbms_handler, instance_client_ref);
+  });
+
+  slk::Save(coordination::PromoteReplicaToMainRes{true}, res_builder);
+}
+
+}  // namespace memgraph::dbms
+#endif

src/dbms/coordinator_handlers.hpp

@@ -0,0 +1,33 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#ifdef MG_ENTERPRISE
+
+#include "slk/serialization.hpp"
+
+namespace memgraph::dbms {
+
+class DbmsHandler;
+
+class CoordinatorHandlers {
+ public:
+  static void Register(DbmsHandler &dbms_handler);
+
+ private:
+  static void PromoteReplicaToMainHandler(DbmsHandler &dbms_handler, slk::Reader *req_reader,
+                                          slk::Builder *res_builder);
+};
+
+}  // namespace memgraph::dbms
+
+#endif

src/dbms/dbms_handler.cpp

@@ -11,6 +11,9 @@
 
 #include "dbms/dbms_handler.hpp"
 
+#include "dbms/coordinator_handlers.hpp"
+#include "flags/replication.hpp"
+
 #include <cstdint>
 #include <filesystem>
 
@@ -225,6 +228,12 @@ DbmsHandler::DbmsHandler(
         "enabling durability by using --storage-snapshot-interval-sec and --storage-wal-enabled flags because "
         "without write-ahead logs this instance is not replicating any data.");
   }
+
+  // MAIN or REPLICA instance
+  if (FLAGS_coordinator_server_port) {
+    CoordinatorHandlers::Register(*this);
+    MG_ASSERT(coordinator_state_.GetCoordinatorServer().Start(), "Failed to start coordinator server!");
+  }
 }
 
 DbmsHandler::DeleteResult DbmsHandler::TryDelete(std::string_view db_name) {
@@ -375,7 +384,7 @@ AllSyncReplicaStatus DbmsHandler::Commit() {
               std::string(main_data.epoch_.id()), last_commited_system_timestamp_,
               system_transaction_->system_timestamp, delta.config);
           // TODO: reduce duplicate code
-          if (!completed && client.mode_ == replication::ReplicationMode::SYNC) {
+          if (!completed && client.mode_ == replication_coordination_glue::ReplicationMode::SYNC) {
             sync_status = AllSyncReplicaStatus::SomeCommitsUnconfirmed;
           }
         }
@@ -399,7 +408,7 @@ AllSyncReplicaStatus DbmsHandler::Commit() {
               std::string(main_data.epoch_.id()), last_commited_system_timestamp_,
               system_transaction_->system_timestamp, delta.uuid);
           // TODO: reduce duplicate code
-          if (!completed && client.mode_ == replication::ReplicationMode::SYNC) {
+          if (!completed && client.mode_ == replication_coordination_glue::ReplicationMode::SYNC) {
             sync_status = AllSyncReplicaStatus::SomeCommitsUnconfirmed;
           }
         }

src/dbms/dbms_handler.hpp

@@ -34,6 +34,7 @@
 #include "storage/v2/transaction.hpp"
 #include "utils/thread_pool.hpp"
 #ifdef MG_ENTERPRISE
+#include "coordination/coordinator_state.hpp"
 #include "dbms/database_handler.hpp"
 #endif
 #include "dbms/transaction.hpp"
@@ -272,6 +273,10 @@ class DbmsHandler {
   bool IsMain() const { return repl_state_.IsMain(); }
   bool IsReplica() const { return repl_state_.IsReplica(); }
 
+#ifdef MG_ENTERPRISE
+  coordination::CoordinatorState &CoordinatorState() { return coordinator_state_; }
+#endif
+
   /**
    * @brief Return the statistics all databases.
    *
@@ -436,7 +441,7 @@ class DbmsHandler {
         return false;
       };
 
-      if (client.mode_ == memgraph::replication::ReplicationMode::ASYNC) {
+      if (client.mode_ == memgraph::replication_coordination_glue::ReplicationMode::ASYNC) {
         client.thread_pool_.AddTask([task = utils::CopyMovableFunctionWrapper{std::move(task)}]() mutable { task(); });
         return true;
       }
@@ -672,6 +677,7 @@ class DbmsHandler {
   storage::Config default_config_;                     //!< Storage configuration used when creating new databases
   DatabaseHandler db_handler_;                         //!< multi-tenancy storage handler
   std::unique_ptr<kvstore::KVStore> durability_;       //!< list of active dbs (pointer so we can postpone its creation)
+  coordination::CoordinatorState coordinator_state_;  //!< Replication coordinator
 #endif
   // TODO: Make an api
  public:

src/dbms/replication_handler.cpp

@@ -18,14 +18,14 @@
 #include "dbms/global.hpp"
 #include "dbms/inmemory/replication_handlers.hpp"
 #include "dbms/replication_client.hpp"
+#include "dbms/utils.hpp"
+#include "replication/messages.hpp"
 #include "replication/state.hpp"
 #include "spdlog/spdlog.h"
 #include "storage/v2/config.hpp"
 #include "storage/v2/replication/rpc.hpp"
 #include "utils/on_scope_exit.hpp"
 
-using memgraph::replication::ReplicationClientConfig;
-using memgraph::replication::ReplicationState;
 using memgraph::replication::RoleMainData;
 using memgraph::replication::RoleReplicaData;
 
@@ -51,34 +51,13 @@ std::string RegisterReplicaErrorToString(RegisterReplicaError error) {
 ReplicationHandler::ReplicationHandler(DbmsHandler &dbms_handler) : dbms_handler_(dbms_handler) {}
 
 bool ReplicationHandler::SetReplicationRoleMain() {
-  auto const main_handler = [](RoleMainData const &) {
+  auto const main_handler = [](RoleMainData &) {
     // If we are already MAIN, we don't want to change anything
     return false;
   };
+
   auto const replica_handler = [this](RoleReplicaData const &) {
-    // STEP 1) bring down all REPLICA servers
+    return memgraph::dbms::DoReplicaToMainPromotion(dbms_handler_);
-    dbms_handler_.ForEach([](DatabaseAccess db_acc) {
-      auto *storage = db_acc->storage();
-      // Remember old epoch + storage timestamp association
-      storage->PrepareForNewEpoch();
-    });
-
-    // STEP 2) Change to MAIN
-    // TODO: restore replication servers if false?
-    if (!dbms_handler_.ReplicationState().SetReplicationRoleMain()) {
-      // TODO: Handle recovery on failure???
-      return false;
-    }
-
-    // STEP 3) We are now MAIN, update storage local epoch
-    const auto &epoch =
-        std::get<RoleMainData>(std::as_const(dbms_handler_.ReplicationState()).ReplicationData()).epoch_;
-    dbms_handler_.ForEach([&](DatabaseAccess db_acc) {
-      auto *storage = db_acc->storage();
-      storage->repl_storage_state_.epoch_ = epoch;
-    });
-
-    return true;
   };
 
   // TODO: under lock
@@ -147,32 +126,12 @@ auto ReplicationHandler::RegisterReplica(const memgraph::replication::Replicatio
   dbms_handler_.SystemRestore(*instance_client.GetValue());
 #endif
 
-  bool all_clients_good = true;
+  const auto dbms_error = memgraph::dbms::HandleErrorOnReplicaClient(instance_client);
-
+  if (dbms_error.has_value()) {
-  // Add database specific clients (NOTE Currently all databases are connected to each replica)
+    return *dbms_error;
-  dbms_handler_.ForEach([&](DatabaseAccess db_acc) {
+  }
-    auto *storage = db_acc->storage();
+  auto &instance_client_ptr = instance_client.GetValue();
-    if (!allow_mt_repl && storage->name() != kDefaultDB) {
+  const bool all_clients_good = memgraph::dbms::RegisterAllDatabasesClients(dbms_handler_, *instance_client_ptr);
-      return;
-    }
-    // TODO: ATM only IN_MEMORY_TRANSACTIONAL, fix other modes
-    if (storage->storage_mode_ != storage::StorageMode::IN_MEMORY_TRANSACTIONAL) return;
-
-    all_clients_good &= storage->repl_storage_state_.replication_clients_.WithLock(
-        [storage, &instance_client, db_acc = std::move(db_acc)](auto &storage_clients) mutable {  // NOLINT
-          auto client = std::make_unique<storage::ReplicationStorageClient>(*instance_client.GetValue());
-          // All good, start replica client
-          client->Start(storage, std::move(db_acc));
-          // After start the storage <-> replica state should be READY or RECOVERING (if correctly started)
-          // MAYBE_BEHIND isn't a statement of the current state, this is the default value
-          // Failed to start due an error like branching of MAIN and REPLICA
-          if (client->State() == storage::replication::ReplicaState::MAYBE_BEHIND) {
-            return false;
-          }
-          storage_clients.push_back(std::move(client));
-          return true;
-        });
-  });
 
   // NOTE Currently if any databases fails, we revert back
   if (!all_clients_good) {

src/dbms/replication_handler.hpp

@@ -15,7 +15,6 @@
 #include "replication/role.hpp"
 #include "utils/result.hpp"
 
-// BEGIN fwd declares
 namespace memgraph::replication {
 struct ReplicationState;
 struct ReplicationServerConfig;
@@ -23,9 +22,11 @@ struct ReplicationClientConfig;
 }  // namespace memgraph::replication
 
 namespace memgraph::dbms {
+
 class DbmsHandler;
 
 enum class RegisterReplicaError : uint8_t { NAME_EXISTS, END_POINT_EXISTS, CONNECTION_FAILED, COULD_NOT_BE_PERSISTED };
+
 enum class UnregisterReplicaResult : uint8_t {
   NOT_MAIN,
   COULD_NOT_BE_PERSISTED,

src/dbms/utils.hpp

@@ -0,0 +1,100 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+#pragma once
+
+#include "dbms/dbms_handler.hpp"
+#include "dbms/replication_handler.hpp"
+#include "replication/include/replication/state.hpp"
+#include "utils/result.hpp"
+
+namespace memgraph::dbms {
+
+inline bool DoReplicaToMainPromotion(dbms::DbmsHandler &dbms_handler) {
+  // STEP 1) bring down all REPLICA servers
+  dbms_handler.ForEach([](DatabaseAccess db_acc) {
+    auto *storage = db_acc->storage();
+    // Remember old epoch + storage timestamp association
+    storage->PrepareForNewEpoch();
+  });
+
+  // STEP 2) Change to MAIN
+  // TODO: restore replication servers if false?
+  if (!dbms_handler.ReplicationState().SetReplicationRoleMain()) {
+    // TODO: Handle recovery on failure???
+    return false;
+  }
+
+  // STEP 3) We are now MAIN, update storage local epoch
+  const auto &epoch =
+      std::get<replication::RoleMainData>(std::as_const(dbms_handler.ReplicationState()).ReplicationData()).epoch_;
+  dbms_handler.ForEach([&](DatabaseAccess db_acc) {
+    auto *storage = db_acc->storage();
+    storage->repl_storage_state_.epoch_ = epoch;
+  });
+
+  return true;
+};
+
+inline bool RegisterAllDatabasesClients(dbms::DbmsHandler &dbms_handler,
+                                        replication::ReplicationClient &instance_client) {
+  if (!allow_mt_repl && dbms_handler.All().size() > 1) {
+    spdlog::warn("Multi-tenant replication is currently not supported!");
+  }
+
+  bool all_clients_good = true;
+
+  // Add database specific clients (NOTE Currently all databases are connected to each replica)
+  dbms_handler.ForEach([&](DatabaseAccess db_acc) {
+    auto *storage = db_acc->storage();
+    if (!allow_mt_repl && storage->name() != kDefaultDB) {
+      return;
+    }
+    // TODO: ATM only IN_MEMORY_TRANSACTIONAL, fix other modes
+    if (storage->storage_mode_ != storage::StorageMode::IN_MEMORY_TRANSACTIONAL) return;
+
+    all_clients_good &= storage->repl_storage_state_.replication_clients_.WithLock(
+        [storage, &instance_client, db_acc = std::move(db_acc)](auto &storage_clients) mutable {  // NOLINT
+          auto client = std::make_unique<storage::ReplicationStorageClient>(instance_client);
+          // All good, start replica client
+          client->Start(storage, std::move(db_acc));
+          // After start the storage <-> replica state should be READY or RECOVERING (if correctly started)
+          // MAYBE_BEHIND isn't a statement of the current state, this is the default value
+          // Failed to start due an error like branching of MAIN and REPLICA
+          if (client->State() == storage::replication::ReplicaState::MAYBE_BEHIND) {
+            return false;
+          }
+          storage_clients.push_back(std::move(client));
+          return true;
+        });
+  });
+
+  return all_clients_good;
+}
+
+inline std::optional<RegisterReplicaError> HandleErrorOnReplicaClient(
+    utils::BasicResult<replication::RegisterReplicaError, replication::ReplicationClient *> &instance_client) {
+  if (instance_client.HasError()) switch (instance_client.GetError()) {
+      case replication::RegisterReplicaError::NOT_MAIN:
+        MG_ASSERT(false, "Only main instance can register a replica!");
+        return {};
+      case replication::RegisterReplicaError::NAME_EXISTS:
+        return dbms::RegisterReplicaError::NAME_EXISTS;
+      case replication::RegisterReplicaError::END_POINT_EXISTS:
+        return dbms::RegisterReplicaError::END_POINT_EXISTS;
+      case replication::RegisterReplicaError::COULD_NOT_BE_PERSISTED:
+        return dbms::RegisterReplicaError::COULD_NOT_BE_PERSISTED;
+      case replication::RegisterReplicaError::SUCCESS:
+        break;
+    }
+  return {};
+}
+
+}  // namespace memgraph::dbms

src/flags/CMakeLists.txt

@@ -6,6 +6,7 @@ add_library(mg-flags STATIC audit.cpp
                             memory_limit.cpp
                             run_time_configurable.cpp
                             storage_mode.cpp
-                            query.cpp)
+                            query.cpp
+                            replication.cpp)
 target_include_directories(mg-flags PUBLIC ${CMAKE_SOURCE_DIR}/include)
 target_link_libraries(mg-flags PUBLIC spdlog::spdlog mg-settings mg-utils)

src/flags/all.hpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -17,5 +17,6 @@
 #include "flags/log_level.hpp"
 #include "flags/memory_limit.hpp"
 #include "flags/query.hpp"
+#include "flags/replication.hpp"
 #include "flags/run_time_configurable.hpp"
 #include "flags/storage_mode.hpp"

src/flags/general.cpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -156,13 +156,6 @@ DEFINE_string(pulsar_service_url, "", "Default URL used while connecting to Puls
 
 // Query flags.
 
-// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
-DEFINE_uint64(replication_replica_check_frequency_sec, 1,
-              "The time duration between two replica checks/pings. If < 1, replicas will NOT be checked at all. NOTE: "
-              "The MAIN instance allocates a new thread for each REPLICA.");
-// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
-DEFINE_bool(replication_restore_state_on_startup, false, "Restore replication state on startup, e.g. recover replica");
-
 DEFINE_VALIDATED_string(query_modules_directory, "",
                         "Directory where modules with custom query procedures are stored. "
                         "NOTE: Multiple comma-separated directories can be defined.",

src/flags/general.hpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -112,11 +112,6 @@ namespace memgraph::flags {
 auto ParseQueryModulesDirectory() -> std::vector<std::filesystem::path>;
 }  // namespace memgraph::flags
 
-// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
-DECLARE_uint64(replication_replica_check_frequency_sec);
-// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
-DECLARE_bool(replication_restore_state_on_startup);
-
 // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
 DECLARE_string(license_key);
 // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)

src/flags/replication.cpp

@@ -0,0 +1,26 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#include "replication.hpp"
+
+#ifdef MG_ENTERPRISE
+// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
+DEFINE_bool(coordinator, false, "Controls whether the instance is a replication coordinator.");
+// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
+DEFINE_uint32(coordinator_server_port, 0, "Port on which coordinator servers will be started.");
+#endif
+
+// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
+DEFINE_uint64(replication_replica_check_frequency_sec, 1,
+              "The time duration between two replica checks/pings. If < 1, replicas will NOT be checked at all. NOTE: "
+              "The MAIN instance allocates a new thread for each REPLICA.");
+// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
+DEFINE_bool(replication_restore_state_on_startup, false, "Restore replication state on startup, e.g. recover replica");

src/flags/replication.hpp

@@ -0,0 +1,26 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include "gflags/gflags.h"
+
+#ifdef MG_ENTERPRISE
+// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
+DECLARE_bool(coordinator);
+// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
+DECLARE_uint32(coordinator_server_port);
+#endif
+
+// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
+DECLARE_uint64(replication_replica_check_frequency_sec);
+// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
+DECLARE_bool(replication_restore_state_on_startup);

src/glue/SessionHL.cpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -193,12 +193,13 @@ std::pair<std::vector<std::string>, std::optional<int>> SessionHL::Interpret(
   for (const auto &[key, bolt_param] : params) {
     params_pv.emplace(key, ToPropertyValue(bolt_param));
   }
+
+#ifdef MG_ENTERPRISE
   const std::string *username{nullptr};
   if (user_) {
     username = &user_->username();
   }
 
-#ifdef MG_ENTERPRISE
   if (memgraph::license::global_license_checker.IsEnterpriseValidFast()) {
     auto &db = interpreter_.current_db_.db_acc_;
     audit_log_->Record(endpoint_.address().to_string(), user_ ? *username : "", query,

src/glue/auth.cpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -66,6 +66,8 @@ auth::Permission PrivilegeToPermission(query::AuthQuery::Privilege privilege) {
       return auth::Permission::MULTI_DATABASE_EDIT;
     case query::AuthQuery::Privilege::MULTI_DATABASE_USE:
       return auth::Permission::MULTI_DATABASE_USE;
+    case query::AuthQuery::Privilege::COORDINATOR:
+      return auth::Permission::COORDINATOR;
   }
 }
 

src/io/CMakeLists.txt

@@ -8,4 +8,5 @@ find_package(fmt REQUIRED)
 find_package(Threads REQUIRED)
 
 add_library(mg-io STATIC ${io_src_files})
+add_library(mg::io ALIAS mg-io)
 target_link_libraries(mg-io stdc++fs Threads::Threads fmt::fmt mg-utils)

src/io/network/endpoint.cpp

@@ -166,7 +166,7 @@ bool Endpoint::IsResolvableAddress(const std::string &address, uint16_t port) {
 }
 
 std::optional<std::pair<std::string, uint16_t>> Endpoint::ParseSocketOrAddress(
-    const std::string &address, const std::optional<uint16_t> default_port = {}) {
+    const std::string &address, const std::optional<uint16_t> default_port) {
   const std::string delimiter = ":";
   std::vector<std::string> parts = utils::Split(address, delimiter);
   if (parts.size() == 1) {

src/memgraph.cpp

@@ -16,7 +16,6 @@
 #include "dbms/constants.hpp"
 #include "dbms/inmemory/replication_handlers.hpp"
 #include "flags/all.hpp"
-#include "flags/run_time_configurable.hpp"
 #include "glue/MonitoringServerT.hpp"
 #include "glue/ServerT.hpp"
 #include "glue/auth_checker.hpp"

src/query/config.hpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source

src/query/exceptions.hpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -259,6 +259,13 @@ class ReplicationModificationInMulticommandTxException : public QueryException {
   SPECIALIZE_GET_EXCEPTION_NAME(ReplicationModificationInMulticommandTxException)
 };
 
+class CoordinatorModificationInMulticommandTxException : public QueryException {
+ public:
+  CoordinatorModificationInMulticommandTxException()
+      : QueryException("Coordinator clause not allowed in multicommand transactions.") {}
+  SPECIALIZE_GET_EXCEPTION_NAME(CoordinatorModificationInMulticommandTxException)
+};
+
 class ReplicationDisabledOnDiskStorage : public QueryException {
  public:
   ReplicationDisabledOnDiskStorage() : QueryException("Replication is not supported while in on-disk storage mode.") {}

src/query/frontend/ast/ast.cpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -239,6 +239,9 @@ constexpr utils::TypeInfo query::DumpQuery::kType{utils::TypeId::AST_DUMP_QUERY,
 constexpr utils::TypeInfo query::ReplicationQuery::kType{utils::TypeId::AST_REPLICATION_QUERY, "ReplicationQuery",
                                                          &query::Query::kType};
 
+constexpr utils::TypeInfo query::CoordinatorQuery::kType{utils::TypeId::AST_COORDINATOR_QUERY, "CoordinatorQuery",
+                                                         &query::Query::kType};
+
 constexpr utils::TypeInfo query::LockPathQuery::kType{utils::TypeId::AST_LOCK_PATH_QUERY, "LockPathQuery",
                                                       &query::Query::kType};
 

src/query/frontend/ast/ast.hpp

@@ -2849,6 +2849,7 @@ class AuthQuery : public memgraph::query::Query {
     TRANSACTION_MANAGEMENT,
     MULTI_DATABASE_EDIT,
     MULTI_DATABASE_USE,
+    COORDINATOR
   };
 
   enum class FineGrainedPrivilege { NOTHING, READ, UPDATE, CREATE_DELETE };
@@ -2927,7 +2928,8 @@ const std::vector<AuthQuery::Privilege> kPrivilegesAll = {AuthQuery::Privilege::
                                                           AuthQuery::Privilege::TRANSACTION_MANAGEMENT,
                                                           AuthQuery::Privilege::STORAGE_MODE,
                                                           AuthQuery::Privilege::MULTI_DATABASE_EDIT,
-                                                          AuthQuery::Privilege::MULTI_DATABASE_USE};
+                                                          AuthQuery::Privilege::MULTI_DATABASE_USE,
+                                                          AuthQuery::Privilege::COORDINATOR};
 
 class DatabaseInfoQuery : public memgraph::query::Query {
  public:
@@ -3039,8 +3041,9 @@ class ReplicationQuery : public memgraph::query::Query {
 
   memgraph::query::ReplicationQuery::Action action_;
   memgraph::query::ReplicationQuery::ReplicationRole role_;
-  std::string replica_name_;
+  std::string instance_name_;
   memgraph::query::Expression *socket_address_{nullptr};
+  memgraph::query::Expression *coordinator_socket_address_{nullptr};
   memgraph::query::Expression *port_{nullptr};
   memgraph::query::ReplicationQuery::SyncMode sync_mode_;
 
@@ -3048,10 +3051,57 @@ class ReplicationQuery : public memgraph::query::Query {
     ReplicationQuery *object = storage->Create<ReplicationQuery>();
     object->action_ = action_;
     object->role_ = role_;
-    object->replica_name_ = replica_name_;
+    object->instance_name_ = instance_name_;
     object->socket_address_ = socket_address_ ? socket_address_->Clone(storage) : nullptr;
     object->port_ = port_ ? port_->Clone(storage) : nullptr;
     object->sync_mode_ = sync_mode_;
+    object->coordinator_socket_address_ =
+        coordinator_socket_address_ ? coordinator_socket_address_->Clone(storage) : nullptr;
+
+    return object;
+  }
+
+ private:
+  friend class AstStorage;
+};
+
+class CoordinatorQuery : public memgraph::query::Query {
+ public:
+  static const utils::TypeInfo kType;
+  const utils::TypeInfo &GetTypeInfo() const override { return kType; }
+
+  enum class Action {
+    REGISTER_MAIN_COORDINATOR_SERVER,
+    REGISTER_REPLICA_COORDINATOR_SERVER,
+    SHOW_REPLICATION_CLUSTER,
+    DO_FAILOVER
+  };
+
+  enum class ReplicationRole { MAIN, REPLICA };
+
+  enum class SyncMode { SYNC, ASYNC };
+
+  CoordinatorQuery() = default;
+
+  DEFVISITABLE(QueryVisitor<void>);
+
+  memgraph::query::CoordinatorQuery::Action action_;
+  memgraph::query::CoordinatorQuery::ReplicationRole role_;
+  std::string instance_name_;
+  memgraph::query::Expression *socket_address_{nullptr};
+  memgraph::query::Expression *coordinator_socket_address_{nullptr};
+  memgraph::query::CoordinatorQuery::SyncMode sync_mode_;
+
+  CoordinatorQuery *Clone(AstStorage *storage) const override {
+    auto *object = storage->Create<CoordinatorQuery>();
+    object->action_ = action_;
+    object->role_ = role_;
+    object->instance_name_ = instance_name_;
+    object->socket_address_ = socket_address_ ? socket_address_->Clone(storage) : nullptr;
+    object->sync_mode_ = sync_mode_;
+    object->coordinator_socket_address_ =
+        coordinator_socket_address_ ? coordinator_socket_address_->Clone(storage) : nullptr;
+
     return object;
   }
 

src/query/frontend/ast/ast_visitor.hpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -108,6 +108,7 @@ class MultiDatabaseQuery;
 class ShowDatabasesQuery;
 class EdgeImportModeQuery;
 class PatternComprehension;
+class CoordinatorQuery;
 
 using TreeCompositeVisitor = utils::CompositeVisitor<
     SingleQuery, CypherUnion, NamedExpression, OrOperator, XorOperator, AndOperator, NotOperator, AdditionOperator,
@@ -146,6 +147,7 @@ class QueryVisitor
                             SystemInfoQuery, ConstraintQuery, DumpQuery, ReplicationQuery, LockPathQuery,
                             FreeMemoryQuery, TriggerQuery, IsolationLevelQuery, CreateSnapshotQuery, StreamQuery,
                             SettingQuery, VersionQuery, ShowConfigQuery, TransactionQueueQuery, StorageModeQuery,
-                            AnalyzeGraphQuery, MultiDatabaseQuery, ShowDatabasesQuery, EdgeImportModeQuery> {};
+                            AnalyzeGraphQuery, MultiDatabaseQuery, ShowDatabasesQuery, EdgeImportModeQuery,
+                            CoordinatorQuery> {};
 
 }  // namespace memgraph::query

src/query/frontend/ast/cypher_main_visitor.cpp

@@ -302,6 +302,13 @@ antlrcpp::Any CypherMainVisitor::visitReplicationQuery(MemgraphCypher::Replicati
   return replication_query;
 }
 
+antlrcpp::Any CypherMainVisitor::visitCoordinatorQuery(MemgraphCypher::CoordinatorQueryContext *ctx) {
+  MG_ASSERT(ctx->children.size() == 1, "CoordinatorQuery should have exactly one child!");
+  auto *coordinator_query = std::any_cast<CoordinatorQuery *>(ctx->children[0]->accept(this));
+  query_ = coordinator_query;
+  return coordinator_query;
+}
+
 antlrcpp::Any CypherMainVisitor::visitEdgeImportModeQuery(MemgraphCypher::EdgeImportModeQueryContext *ctx) {
   auto *edge_import_mode_query = storage_->Create<EdgeImportModeQuery>();
   if (ctx->ACTIVE()) {
@@ -316,24 +323,34 @@ antlrcpp::Any CypherMainVisitor::visitEdgeImportModeQuery(MemgraphCypher::EdgeIm
 antlrcpp::Any CypherMainVisitor::visitSetReplicationRole(MemgraphCypher::SetReplicationRoleContext *ctx) {
   auto *replication_query = storage_->Create<ReplicationQuery>();
   replication_query->action_ = ReplicationQuery::Action::SET_REPLICATION_ROLE;
+
+  auto set_replication_port = [replication_query, ctx, this]() -> void {
+    if (ctx->port->numberLiteral() && ctx->port->numberLiteral()->integerLiteral()) {
+      replication_query->port_ = std::any_cast<Expression *>(ctx->port->accept(this));
+    } else {
+      throw SyntaxException("Port must be an integer literal!");
+    }
+  };
+
   if (ctx->MAIN()) {
+    replication_query->role_ = ReplicationQuery::ReplicationRole::MAIN;
     if (ctx->WITH() || ctx->PORT()) {
       throw SemanticException("Main can't set a port!");
     }
-    replication_query->role_ = ReplicationQuery::ReplicationRole::MAIN;
+
   } else if (ctx->REPLICA()) {
     replication_query->role_ = ReplicationQuery::ReplicationRole::REPLICA;
     if (ctx->WITH() && ctx->PORT()) {
-      if (ctx->port->numberLiteral() && ctx->port->numberLiteral()->integerLiteral()) {
+      set_replication_port();
-        replication_query->port_ = std::any_cast<Expression *>(ctx->port->accept(this));
+    } else {
-      } else {
+      throw SemanticException("Replica must set a port!");
-        throw SyntaxException("Port must be an integer literal!");
-      }
     }
   }
+
   return replication_query;
 }
-antlrcpp::Any CypherMainVisitor::visitShowReplicationRole(MemgraphCypher::ShowReplicationRoleContext *ctx) {
+
+antlrcpp::Any CypherMainVisitor::visitShowReplicationRole(MemgraphCypher::ShowReplicationRoleContext * /*ctx*/) {
   auto *replication_query = storage_->Create<ReplicationQuery>();
   replication_query->action_ = ReplicationQuery::Action::SHOW_REPLICATION_ROLE;
   return replication_query;
@@ -342,7 +359,7 @@ antlrcpp::Any CypherMainVisitor::visitShowReplicationRole(MemgraphCypher::ShowRe
 antlrcpp::Any CypherMainVisitor::visitRegisterReplica(MemgraphCypher::RegisterReplicaContext *ctx) {
   auto *replication_query = storage_->Create<ReplicationQuery>();
   replication_query->action_ = ReplicationQuery::Action::REGISTER_REPLICA;
-  replication_query->replica_name_ = std::any_cast<std::string>(ctx->replicaName()->symbolicName()->accept(this));
+  replication_query->instance_name_ = std::any_cast<std::string>(ctx->instanceName()->symbolicName()->accept(this));
   if (ctx->SYNC()) {
     replication_query->sync_mode_ = memgraph::query::ReplicationQuery::SyncMode::SYNC;
   } else if (ctx->ASYNC()) {
@@ -351,26 +368,90 @@ antlrcpp::Any CypherMainVisitor::visitRegisterReplica(MemgraphCypher::RegisterRe
 
   if (!ctx->socketAddress()->literal()->StringLiteral()) {
     throw SemanticException("Socket address should be a string literal!");
-  } else {
-    replication_query->socket_address_ = std::any_cast<Expression *>(ctx->socketAddress()->accept(this));
   }
+  replication_query->socket_address_ = std::any_cast<Expression *>(ctx->socketAddress()->accept(this));
 
   return replication_query;
 }
 
+// License check is done in the interpreter.
+antlrcpp::Any CypherMainVisitor::visitRegisterCoordinatorServer(MemgraphCypher::RegisterCoordinatorServerContext *ctx) {
+  MG_ASSERT(ctx->children.size() == 1, "RegisterCoordinatorServerQuery should have exactly one child!");
+  auto *coordinator_query = std::any_cast<CoordinatorQuery *>(ctx->children[0]->accept(this));
+  query_ = coordinator_query;
+  return coordinator_query;
+}
+
+// License check is done in the interpreter
+antlrcpp::Any CypherMainVisitor::visitShowReplicationCluster(MemgraphCypher::ShowReplicationClusterContext * /*ctx*/) {
+  auto *coordinator_query = storage_->Create<CoordinatorQuery>();
+  coordinator_query->action_ = CoordinatorQuery::Action::SHOW_REPLICATION_CLUSTER;
+  return coordinator_query;
+}
+
+// License check is done in the interpreter
+antlrcpp::Any CypherMainVisitor::visitRegisterReplicaCoordinatorServer(
+    MemgraphCypher::RegisterReplicaCoordinatorServerContext *ctx) {
+  auto *coordinator_query = storage_->Create<CoordinatorQuery>();
+  if (!ctx->socketAddress()->literal()->StringLiteral()) {
+    throw SemanticException("Socket address should be a string literal!");
+  }
+
+  if (!ctx->coordinatorSocketAddress()->literal()->StringLiteral()) {
+    throw SemanticException("Coordinator socket address should be a string literal!");
+  }
+  coordinator_query->action_ = CoordinatorQuery::Action::REGISTER_REPLICA_COORDINATOR_SERVER;
+  coordinator_query->role_ = CoordinatorQuery::ReplicationRole::REPLICA;
+  coordinator_query->socket_address_ = std::any_cast<Expression *>(ctx->socketAddress()->accept(this));
+  coordinator_query->coordinator_socket_address_ =
+      std::any_cast<Expression *>(ctx->coordinatorSocketAddress()->accept(this));
+  coordinator_query->instance_name_ = std::any_cast<std::string>(ctx->instanceName()->symbolicName()->accept(this));
+  if (ctx->SYNC()) {
+    coordinator_query->sync_mode_ = memgraph::query::CoordinatorQuery::SyncMode::SYNC;
+  } else if (ctx->ASYNC()) {
+    coordinator_query->sync_mode_ = memgraph::query::CoordinatorQuery::SyncMode::ASYNC;
+  }
+
+  return coordinator_query;
+}
+
+// License check is done in the interpreter
+antlrcpp::Any CypherMainVisitor::visitRegisterMainCoordinatorServer(
+    MemgraphCypher::RegisterMainCoordinatorServerContext *ctx) {
+  if (!ctx->coordinatorSocketAddress()->literal()->StringLiteral()) {
+    throw SemanticException("Coordinator socket address should be a string literal!");
+  }
+  auto *coordinator_query = storage_->Create<CoordinatorQuery>();
+  coordinator_query->action_ = CoordinatorQuery::Action::REGISTER_MAIN_COORDINATOR_SERVER;
+  coordinator_query->role_ = CoordinatorQuery::ReplicationRole::MAIN;
+  coordinator_query->coordinator_socket_address_ =
+      std::any_cast<Expression *>(ctx->coordinatorSocketAddress()->accept(this));
+  coordinator_query->instance_name_ = std::any_cast<std::string>(ctx->instanceName()->symbolicName()->accept(this));
+
+  return coordinator_query;
+}
+
 antlrcpp::Any CypherMainVisitor::visitDropReplica(MemgraphCypher::DropReplicaContext *ctx) {
   auto *replication_query = storage_->Create<ReplicationQuery>();
   replication_query->action_ = ReplicationQuery::Action::DROP_REPLICA;
-  replication_query->replica_name_ = std::any_cast<std::string>(ctx->replicaName()->symbolicName()->accept(this));
+  replication_query->instance_name_ = std::any_cast<std::string>(ctx->instanceName()->symbolicName()->accept(this));
   return replication_query;
 }
 
-antlrcpp::Any CypherMainVisitor::visitShowReplicas(MemgraphCypher::ShowReplicasContext *ctx) {
+antlrcpp::Any CypherMainVisitor::visitShowReplicas(MemgraphCypher::ShowReplicasContext * /*ctx*/) {
   auto *replication_query = storage_->Create<ReplicationQuery>();
   replication_query->action_ = ReplicationQuery::Action::SHOW_REPLICAS;
   return replication_query;
 }
 
+// License check is done in the interpreter
+antlrcpp::Any CypherMainVisitor::visitDoFailover(MemgraphCypher::DoFailoverContext * /*ctx*/) {
+  auto *coordinator_query = storage_->Create<CoordinatorQuery>();
+  coordinator_query->action_ = CoordinatorQuery::Action::DO_FAILOVER;
+  query_ = coordinator_query;
+  return coordinator_query;
+}
+
 antlrcpp::Any CypherMainVisitor::visitLockPathQuery(MemgraphCypher::LockPathQueryContext *ctx) {
   auto *lock_query = storage_->Create<LockPathQuery>();
   if (ctx->STATUS()) {
@@ -1638,6 +1719,7 @@ antlrcpp::Any CypherMainVisitor::visitPrivilege(MemgraphCypher::PrivilegeContext
   if (ctx->STORAGE_MODE()) return AuthQuery::Privilege::STORAGE_MODE;
   if (ctx->MULTI_DATABASE_EDIT()) return AuthQuery::Privilege::MULTI_DATABASE_EDIT;
   if (ctx->MULTI_DATABASE_USE()) return AuthQuery::Privilege::MULTI_DATABASE_USE;
+  if (ctx->COORDINATOR()) return AuthQuery::Privilege::COORDINATOR;
   LOG_FATAL("Should not get here - unknown privilege!");
 }
 

src/query/frontend/ast/cypher_main_visitor.hpp

@@ -233,6 +233,37 @@ class CypherMainVisitor : public antlropencypher::MemgraphCypherBaseVisitor {
    */
   antlrcpp::Any visitShowReplicas(MemgraphCypher::ShowReplicasContext *ctx) override;
 
+  /**
+   * @return CoordinatorQuery*
+   */
+  antlrcpp::Any visitCoordinatorQuery(MemgraphCypher::CoordinatorQueryContext *ctx) override;
+
+  /**
+   * @return CoordinatorQuery*
+   */
+  antlrcpp::Any visitRegisterCoordinatorServer(MemgraphCypher::RegisterCoordinatorServerContext *ctx) override;
+
+  /**
+   * @return CoordinatorQuery*
+   */
+  antlrcpp::Any visitRegisterMainCoordinatorServer(MemgraphCypher::RegisterMainCoordinatorServerContext *ctx) override;
+
+  /**
+   * @return CoordinatorQuery*
+   */
+  antlrcpp::Any visitRegisterReplicaCoordinatorServer(
+      MemgraphCypher::RegisterReplicaCoordinatorServerContext *ctx) override;
+
+  /**
+   * @return CoordinatorQuery*
+   */
+  antlrcpp::Any visitShowReplicationCluster(MemgraphCypher::ShowReplicationClusterContext *ctx) override;
+
+  /**
+   * @return CoordinatorQuery*
+   */
+  antlrcpp::Any visitDoFailover(MemgraphCypher::DoFailoverContext *ctx) override;
+
   /**
    * @return LockPathQuery*
    */

src/query/frontend/opencypher/grammar/MemgraphCypher.g4

@@ -48,10 +48,12 @@ memgraphCypherKeyword : cypherKeyword
                       | DATABASE
                       | DENY
                       | DROP
+                      | DO
                       | DUMP
                       | EDGE
                       | EDGE_TYPES
                       | EXECUTE
+                      | FAILOVER
                       | FOR
                       | FOREACH
                       | FREE
@@ -151,6 +153,7 @@ query : cypherQuery
       | multiDatabaseQuery
       | showDatabases
       | edgeImportModeQuery
+      | coordinatorQuery
       ;
 
 cypherQuery : ( indexHints )? singleQuery ( cypherUnion )* ( queryMemoryLimit )? ;
@@ -183,6 +186,11 @@ replicationQuery : setReplicationRole
                  | showReplicas
                  ;
 
+coordinatorQuery : registerCoordinatorServer
+                 | showReplicationCluster
+                 | doFailover
+                 ;
+
 triggerQuery : createTrigger
              | dropTrigger
              | showTriggers
@@ -244,6 +252,8 @@ transactionQueueQuery : showTransactions
 
 showTransactions : SHOW TRANSACTIONS ;
 
+doFailover : DO FAILOVER ;
+
 terminateTransactions : TERMINATE TRANSACTIONS transactionIdList;
 
 loadCsv : LOAD CSV FROM csvFile ( WITH | NO ) HEADER
@@ -323,6 +333,7 @@ privilege : CREATE
           | STORAGE_MODE
           | MULTI_DATABASE_EDIT
           | MULTI_DATABASE_USE
+          | COORDINATOR
           ;
 
 granularPrivilege : NOTHING | READ | UPDATE | CREATE_DELETE ;
@@ -364,14 +375,24 @@ setReplicationRole : SET REPLICATION ROLE TO ( MAIN | REPLICA )
 
 showReplicationRole : SHOW REPLICATION ROLE ;
 
-replicaName : symbolicName ;
+showReplicationCluster : SHOW REPLICATION CLUSTER ;
+
+instanceName : symbolicName ;
 
 socketAddress : literal ;
 
-registerReplica : REGISTER REPLICA replicaName ( SYNC | ASYNC )
+coordinatorSocketAddress : literal ;
+
+registerReplica : REGISTER REPLICA instanceName ( SYNC | ASYNC )
                 TO socketAddress ;
 
-dropReplica : DROP REPLICA replicaName ;
+registerReplicaCoordinatorServer: REGISTER REPLICA instanceName ( ASYNC | SYNC ) TO socketAddress WITH COORDINATOR SERVER ON coordinatorSocketAddress ;
+
+registerMainCoordinatorServer: REGISTER MAIN instanceName WITH COORDINATOR SERVER ON coordinatorSocketAddress ;
+
+registerCoordinatorServer : registerMainCoordinatorServer | registerReplicaCoordinatorServer ;
+
+dropReplica : DROP REPLICA instanceName ;
 
 showReplicas : SHOW REPLICAS ;
 

src/query/frontend/opencypher/grammar/MemgraphCypherLexer.g4

@@ -39,15 +39,18 @@ BOOTSTRAP_SERVERS       : B O O T S T R A P UNDERSCORE S E R V E R S ;
 CALL                    : C A L L ;
 CHECK                   : C H E C K ;
 CLEAR                   : C L E A R ;
+CLUSTER                 : C L U S T E R ;
 COMMIT                  : C O M M I T ;
 COMMITTED               : C O M M I T T E D ;
 CONFIG                  : C O N F I G ;
 CONFIGS                 : C O N F I G S;
 CONSUMER_GROUP          : C O N S U M E R UNDERSCORE G R O U P ;
+COORDINATOR             : C O O R D I N A T O R ;
 CREATE_DELETE           : C R E A T E UNDERSCORE D E L E T E ;
 CREDENTIALS             : C R E D E N T I A L S ;
 CSV                     : C S V ;
 DATA                    : D A T A ;
+DO                      : D O ;
 DELIMITER               : D E L I M I T E R ;
 DATABASE                : D A T A B A S E ;
 DATABASES               : D A T A B A S E S ;
@@ -59,6 +62,7 @@ DURABILITY              : D U R A B I L I T Y ;
 EDGE                    : E D G E ;
 EDGE_TYPES              : E D G E UNDERSCORE T Y P E S ;
 EXECUTE                 : E X E C U T E ;
+FAILOVER                : F A I L O V E R ;
 FOR                     : F O R ;
 FOREACH                 : F O R E A C H;
 FREE                    : F R E E ;
@@ -107,6 +111,7 @@ REVOKE                  : R E V O K E ;
 ROLE                    : R O L E ;
 ROLES                   : R O L E S ;
 QUOTE                   : Q U O T E ;
+SERVER                  : S E R V E R ;
 SERVICE_URL             : S E R V I C E UNDERSCORE U R L ;
 SESSION                 : S E S S I O N ;
 SETTING                 : S E T T I N G ;

src/query/frontend/semantic/required_privileges.cpp

@@ -116,6 +116,8 @@ class PrivilegeExtractor : public QueryVisitor<void>, public HierarchicalTreeVis
     AddPrivilege(AuthQuery::Privilege::MULTI_DATABASE_USE); /* OR EDIT */
   }
 
+  void Visit(CoordinatorQuery & /*coordinator_query*/) override { AddPrivilege(AuthQuery::Privilege::COORDINATOR); }
+
   bool PreVisit(Create & /*unused*/) override {
     AddPrivilege(AuthQuery::Privilege::CREATE);
     return false;

src/query/interpreter.cpp

@@ -35,9 +35,9 @@
 #include "auth/models.hpp"
 #include "csv/parsing.hpp"
 #include "dbms/database.hpp"
-#include "dbms/dbms_handler.hpp"
 #include "dbms/global.hpp"
 #include "dbms/inmemory/storage_helper.hpp"
+#include "flags/replication.hpp"
 #include "flags/run_time_configurable.hpp"
 #include "glue/communication.hpp"
 #include "license/license.hpp"
@@ -101,12 +101,18 @@
 #include "utils/typeinfo.hpp"
 #include "utils/variant_helpers.hpp"
 
+#include "dbms/coordinator_handler.hpp"
 #include "dbms/dbms_handler.hpp"
 #include "dbms/replication_handler.hpp"
 #include "query/auth_query_handler.hpp"
 #include "query/interpreter_context.hpp"
 #include "replication/state.hpp"
 
+#ifdef MG_ENTERPRISE
+#include "coordination/constants.hpp"
+#include "coordination/coordinator_entity_info.hpp"
+#endif
+
 namespace memgraph::metrics {
 extern Event ReadQuery;
 extern Event WriteQuery;
@@ -121,6 +127,7 @@ extern const Event CommitedTransactions;
 extern const Event RollbackedTransactions;
 extern const Event ActiveTransactions;
 }  // namespace memgraph::metrics
+
 void memgraph::query::CurrentDB::SetupDatabaseTransaction(
     std::optional<storage::IsolationLevel> override_isolation_level, bool could_commit, bool unique) {
   auto &db_acc = *db_acc_;
@@ -260,17 +267,32 @@ bool IsAllShortestPathsQuery(const std::vector<memgraph::query::Clause *> &claus
   return false;
 }
 
-inline auto convertToReplicationMode(const ReplicationQuery::SyncMode &sync_mode) -> replication::ReplicationMode {
+inline auto convertFromCoordinatorToReplicationMode(const CoordinatorQuery::SyncMode &sync_mode)
+    -> replication_coordination_glue::ReplicationMode {
   switch (sync_mode) {
-    case ReplicationQuery::SyncMode::ASYNC: {
+    case CoordinatorQuery::SyncMode::ASYNC: {
-      return replication::ReplicationMode::ASYNC;
+      return replication_coordination_glue::ReplicationMode::ASYNC;
     }
-    case ReplicationQuery::SyncMode::SYNC: {
+    case CoordinatorQuery::SyncMode::SYNC: {
-      return replication::ReplicationMode::SYNC;
+      return replication_coordination_glue::ReplicationMode::SYNC;
     }
   }
   // TODO: C++23 std::unreachable()
-  return replication::ReplicationMode::ASYNC;
+  return replication_coordination_glue::ReplicationMode::ASYNC;
+}
+
+inline auto convertToReplicationMode(const ReplicationQuery::SyncMode &sync_mode)
+    -> replication_coordination_glue::ReplicationMode {
+  switch (sync_mode) {
+    case ReplicationQuery::SyncMode::ASYNC: {
+      return replication_coordination_glue::ReplicationMode::ASYNC;
+    }
+    case ReplicationQuery::SyncMode::SYNC: {
+      return replication_coordination_glue::ReplicationMode::SYNC;
+    }
+  }
+  // TODO: C++23 std::unreachable()
+  return replication_coordination_glue::ReplicationMode::ASYNC;
 }
 
 class ReplQueryHandler {
@@ -289,14 +311,17 @@ class ReplQueryHandler {
 
   /// @throw QueryRuntimeException if an error ocurred.
   void SetReplicationRole(ReplicationQuery::ReplicationRole replication_role, std::optional<int64_t> port) {
-    if (replication_role == ReplicationQuery::ReplicationRole::MAIN) {
+    auto ValidatePort = [](std::optional<int64_t> port) -> void {
-      if (!handler_.SetReplicationRoleMain()) {
+      if (*port < 0 || *port > std::numeric_limits<uint16_t>::max()) {
-        throw QueryRuntimeException("Couldn't set role to main!");
-      }
-    } else {
-      if (!port || *port < 0 || *port > std::numeric_limits<uint16_t>::max()) {
         throw QueryRuntimeException("Port number invalid!");
       }
+    };
+    if (replication_role == ReplicationQuery::ReplicationRole::MAIN) {
+      if (!handler_.SetReplicationRoleMain()) {
+        throw QueryRuntimeException("Couldn't set replication role to main!");
+      }
+    } else {
+      ValidatePort(port);
 
       auto const config = memgraph::replication::ReplicationServerConfig{
           .ip_address = memgraph::replication::kDefaultReplicationServerIp,
@@ -323,27 +348,33 @@ class ReplQueryHandler {
   /// @throw QueryRuntimeException if an error ocurred.
   void RegisterReplica(const std::string &name, const std::string &socket_address,
                        const ReplicationQuery::SyncMode sync_mode, const std::chrono::seconds replica_check_frequency) {
+    // Coordinator is main by default so this check is OK although it should actually be nothing (neither main nor
+    // replica)
     if (handler_.IsReplica()) {
       // replica can't register another replica
       throw QueryRuntimeException("Replica can't register another replica!");
     }
 
-    auto repl_mode = convertToReplicationMode(sync_mode);
+    const auto repl_mode = convertToReplicationMode(sync_mode);
 
-    auto maybe_ip_and_port =
+    const auto maybe_ip_and_port =
         io::network::Endpoint::ParseSocketOrAddress(socket_address, memgraph::replication::kDefaultReplicationPort);
     if (maybe_ip_and_port) {
-      auto [ip, port] = *maybe_ip_and_port;
+      const auto [ip, port] = *maybe_ip_and_port;
-      auto config = replication::ReplicationClientConfig{.name = name,
+      const auto replication_config =
-                                                         .mode = repl_mode,
+          replication::ReplicationClientConfig{.name = name,
-                                                         .ip_address = ip,
+                                               .mode = repl_mode,
-                                                         .port = port,
+                                               .ip_address = ip,
-                                                         .replica_check_frequency = replica_check_frequency,
+                                               .port = port,
-                                                         .ssl = std::nullopt};
+                                               .replica_check_frequency = replica_check_frequency,
-      auto ret = handler_.RegisterReplica(config);
+                                               .ssl = std::nullopt};
-      if (ret.HasError()) {
+
+      const auto error = handler_.RegisterReplica(replication_config).HasError();
+
+      if (error) {
         throw QueryRuntimeException(fmt::format("Couldn't register replica '{}'!", name));
       }
+
     } else {
       throw QueryRuntimeException("Invalid socket address!");
     }
@@ -382,10 +413,10 @@ class ReplQueryHandler {
       replica.name = repl_info.name;
       replica.socket_address = repl_info.endpoint.SocketAddress();
       switch (repl_info.mode) {
-        case memgraph::replication::ReplicationMode::SYNC:
+        case replication_coordination_glue::ReplicationMode::SYNC:
           replica.sync_mode = ReplicationQuery::SyncMode::SYNC;
           break;
-        case memgraph::replication::ReplicationMode::ASYNC:
+        case replication_coordination_glue::ReplicationMode::ASYNC:
           replica.sync_mode = ReplicationQuery::SyncMode::ASYNC;
           break;
       }
@@ -420,6 +451,140 @@ class ReplQueryHandler {
   dbms::ReplicationHandler handler_;
 };
 
+class CoordQueryHandler final : public query::CoordinatorQueryHandler {
+ public:
+  explicit CoordQueryHandler(dbms::DbmsHandler *dbms_handler) : handler_ { *dbms_handler }
+#ifdef MG_ENTERPRISE
+  , coordinator_handler_(*dbms_handler)
+#endif
+  {
+  }
+
+#ifdef MG_ENTERPRISE
+  /// @throw QueryRuntimeException if an error ocurred.
+  void RegisterReplicaCoordinatorServer(const std::string &replication_socket_address,
+                                        const std::string &coordinator_socket_address,
+                                        const std::chrono::seconds instance_check_frequency,
+                                        const std::string &instance_name,
+                                        CoordinatorQuery::SyncMode sync_mode) override {
+    const auto maybe_replication_ip_port =
+        io::network::Endpoint::ParseSocketOrAddress(replication_socket_address, std::nullopt);
+    if (!maybe_replication_ip_port) {
+      throw QueryRuntimeException("Invalid replication socket address!");
+    }
+
+    const auto maybe_coordinator_ip_port =
+        io::network::Endpoint::ParseSocketOrAddress(coordinator_socket_address, std::nullopt);
+    if (!maybe_replication_ip_port) {
+      throw QueryRuntimeException("Invalid replication socket address!");
+    }
+
+    const auto [replication_ip, replication_port] = *maybe_replication_ip_port;
+    const auto [coordinator_server_ip, coordinator_server_port] = *maybe_coordinator_ip_port;
+    const auto repl_config = coordination::CoordinatorClientConfig::ReplicationClientInfo{
+        .instance_name = instance_name,
+        .replication_mode = convertFromCoordinatorToReplicationMode(sync_mode),
+        .replication_ip_address = replication_ip,
+        .replication_port = replication_port};
+
+    const auto coordinator_client_config =
+        coordination::CoordinatorClientConfig{.instance_name = instance_name,
+                                              .ip_address = coordinator_server_ip,
+                                              .port = coordinator_server_port,
+                                              .health_check_frequency_sec = instance_check_frequency,
+                                              .replication_client_info = repl_config,
+                                              .ssl = std::nullopt};
+
+    if (const auto ret = coordinator_handler_.RegisterReplicaOnCoordinator(coordinator_client_config); ret.HasError()) {
+      throw QueryRuntimeException("Couldn't register replica on coordinator!");
+    }
+  }
+
+  void RegisterMainCoordinatorServer(const std::string &coordinator_socket_address,
+                                     const std::chrono::seconds instance_check_frequency,
+                                     const std::string &instance_name) override {
+    const auto maybe_ip_and_port =
+        io::network::Endpoint::ParseSocketOrAddress(coordinator_socket_address, std::nullopt);
+    if (!maybe_ip_and_port) {
+      throw QueryRuntimeException("Invalid socket address!");
+    }
+    const auto [ip, port] = *maybe_ip_and_port;
+    const auto config = coordination::CoordinatorClientConfig{.instance_name = instance_name,
+                                                              .ip_address = ip,
+                                                              .port = port,
+                                                              .health_check_frequency_sec = instance_check_frequency,
+                                                              .ssl = std::nullopt};
+
+    if (const auto ret = coordinator_handler_.RegisterMainOnCoordinator(config); ret.HasError()) {
+      throw QueryRuntimeException("Couldn't register main on coordinator!");
+    }
+  }
+
+  /// @throw QueryRuntimeException if an error ocurred.
+  void DoFailover() const override {
+    if (!FLAGS_coordinator) {
+      throw QueryRuntimeException("Only coordinator can register coordinator server!");
+    }
+
+    auto status = coordinator_handler_.DoFailover();
+    switch (status) {
+      using enum memgraph::dbms::DoFailoverStatus;
+      case ALL_REPLICAS_DOWN:
+        throw QueryRuntimeException("Failover aborted since all replicas are down!");
+      case MAIN_ALIVE:
+        throw QueryRuntimeException("Failover aborted since main is alive!");
+      case CLUSTER_UNINITIALIZED:
+        throw QueryRuntimeException("Failover aborted since cluster is uninitialized!");
+      case SUCCESS:
+        break;
+    }
+  }
+
+  std::vector<MainReplicaStatus> ShowMainReplicaStatus(
+      const std::vector<coordination::CoordinatorEntityInfo> &replicas,
+      const std::unordered_map<std::string_view, bool> &health_check_replicas,
+      const std::optional<coordination::CoordinatorEntityInfo> &main,
+      const std::optional<coordination::CoordinatorEntityHealthInfo> &health_check_main) const override {
+    std::vector<MainReplicaStatus> result{};
+    result.reserve(replicas.size() + 1);  // replicas + 1 main
+    std::ranges::transform(
+        replicas, std::back_inserter(result), [&health_check_replicas](const auto &replica) -> MainReplicaStatus {
+          return {replica.name, replica.endpoint.SocketAddress(), health_check_replicas.at(replica.name), false};
+        });
+    if (main) {
+      bool is_main_alive = health_check_main.has_value() ? health_check_main.value().alive : false;
+      result.emplace_back(main->name, main->endpoint.SocketAddress(), is_main_alive, true);
+    }
+    return result;
+  }
+
+#endif
+
+#ifdef MG_ENTERPRISE
+  std::vector<coordination::CoordinatorEntityInfo> ShowReplicasOnCoordinator() const override {
+    return coordinator_handler_.ShowReplicasOnCoordinator();
+  }
+
+  std::unordered_map<std::string_view, bool> PingReplicasOnCoordinator() const override {
+    return coordinator_handler_.PingReplicasOnCoordinator();
+  }
+
+  std::optional<coordination::CoordinatorEntityInfo> ShowMainOnCoordinator() const override {
+    return coordinator_handler_.ShowMainOnCoordinator();
+  }
+
+  std::optional<coordination::CoordinatorEntityHealthInfo> PingMainOnCoordinator() const override {
+    return coordinator_handler_.PingMainOnCoordinator();
+  }
+#endif
+
+ private:
+  dbms::ReplicationHandler handler_;
+#ifdef MG_ENTERPRISE
+  dbms::CoordinatorHandler coordinator_handler_;
+#endif
+};
+
 /// returns false if the replication role can't be set
 /// @throw QueryRuntimeException if an error ocurred.
 
@@ -723,6 +888,15 @@ Callback HandleReplicationQuery(ReplicationQuery *repl_query, const Parameters &
   Callback callback;
   switch (repl_query->action_) {
     case ReplicationQuery::Action::SET_REPLICATION_ROLE: {
+#ifdef MG_ENTERPRISE
+      if (FLAGS_coordinator) {
+        if (repl_query->role_ == ReplicationQuery::ReplicationRole::REPLICA) {
+          throw QueryRuntimeException("Coordinator cannot become a replica!");
+        }
+        throw QueryRuntimeException("Coordinator cannot become main!");
+      }
+#endif
+
       auto port = EvaluateOptionalExpression(repl_query->port_, evaluator);
       std::optional<int64_t> maybe_port;
       if (port.IsInt()) {
@@ -743,6 +917,12 @@ Callback HandleReplicationQuery(ReplicationQuery *repl_query, const Parameters &
       return callback;
     }
     case ReplicationQuery::Action::SHOW_REPLICATION_ROLE: {
+#ifdef MG_ENTERPRISE
+      if (FLAGS_coordinator) {
+        throw QueryRuntimeException("Coordinator doesn't have a replication role!");
+      }
+#endif
+
       callback.header = {"replication role"};
       callback.fn = [handler = ReplQueryHandler{dbms_handler}] {
         auto mode = handler.ShowReplicationRole();
@@ -758,7 +938,7 @@ Callback HandleReplicationQuery(ReplicationQuery *repl_query, const Parameters &
       return callback;
     }
     case ReplicationQuery::Action::REGISTER_REPLICA: {
-      const auto &name = repl_query->replica_name_;
+      const auto &name = repl_query->instance_name_;
       const auto &sync_mode = repl_query->sync_mode_;
       auto socket_address = repl_query->socket_address_->Accept(evaluator);
       const auto replica_check_frequency = config.replication_replica_check_frequency;
@@ -769,20 +949,27 @@ Callback HandleReplicationQuery(ReplicationQuery *repl_query, const Parameters &
         return std::vector<std::vector<TypedValue>>();
       };
       notifications->emplace_back(SeverityLevel::INFO, NotificationCode::REGISTER_REPLICA,
-                                  fmt::format("Replica {} is registered.", repl_query->replica_name_));
+                                  fmt::format("Replica {} is registered.", repl_query->instance_name_));
       return callback;
     }
+
     case ReplicationQuery::Action::DROP_REPLICA: {
-      const auto &name = repl_query->replica_name_;
+      const auto &name = repl_query->instance_name_;
       callback.fn = [handler = ReplQueryHandler{dbms_handler}, name]() mutable {
         handler.DropReplica(name);
         return std::vector<std::vector<TypedValue>>();
       };
       notifications->emplace_back(SeverityLevel::INFO, NotificationCode::DROP_REPLICA,
-                                  fmt::format("Replica {} is dropped.", repl_query->replica_name_));
+                                  fmt::format("Replica {} is dropped.", repl_query->instance_name_));
       return callback;
     }
     case ReplicationQuery::Action::SHOW_REPLICAS: {
+#ifdef MG_ENTERPRISE
+      if (FLAGS_coordinator) {
+        throw QueryRuntimeException("Coordinator cannot call SHOW REPLICAS! Use SHOW REPLICATION CLUSTER instead.");
+      }
+#endif
+
       callback.header = {
           "name", "socket_address", "sync_mode", "current_timestamp_of_replica", "number_of_timestamp_behind_master",
           "state"};
@@ -834,6 +1021,154 @@ Callback HandleReplicationQuery(ReplicationQuery *repl_query, const Parameters &
   }
 }
 
+Callback HandleCoordinatorQuery(CoordinatorQuery *coordinator_query, const Parameters &parameters,
+                                dbms::DbmsHandler *dbms_handler, const query::InterpreterConfig &config,
+                                std::vector<Notification> *notifications) {
+  Callback callback;
+  switch (coordinator_query->action_) {
+    case CoordinatorQuery::Action::REGISTER_MAIN_COORDINATOR_SERVER: {
+      if (!license::global_license_checker.IsEnterpriseValidFast()) {
+        throw QueryException("Trying to use enterprise feature without a valid license.");
+      }
+#ifdef MG_ENTERPRISE
+      if constexpr (!coordination::allow_ha) {
+        throw QueryRuntimeException(
+            "High availability is experimental feature. Please set MG_EXPERIMENTAL_HIGH_AVAILABILITY compile flag to "
+            "be able to use this functionality.");
+      }
+      if (!FLAGS_coordinator) {
+        throw QueryRuntimeException("Only coordinator can register coordinator server!");
+      }
+      // TODO: MemoryResource for EvaluationContext, it should probably be passed as
+      // the argument to Callback.
+      EvaluationContext evaluation_context{.timestamp = QueryTimestamp(), .parameters = parameters};
+      auto evaluator = PrimitiveLiteralExpressionEvaluator{evaluation_context};
+
+      auto coordinator_socket_address_tv = coordinator_query->coordinator_socket_address_->Accept(evaluator);
+      callback.fn = [handler = CoordQueryHandler{dbms_handler}, coordinator_socket_address_tv,
+                     main_check_frequency = config.replication_replica_check_frequency,
+                     instance_name = coordinator_query->instance_name_]() mutable {
+        handler.RegisterMainCoordinatorServer(std::string(coordinator_socket_address_tv.ValueString()),
+                                              main_check_frequency, instance_name);
+        return std::vector<std::vector<TypedValue>>();
+      };
+
+      notifications->emplace_back(
+          SeverityLevel::INFO, NotificationCode::REGISTER_COORDINATOR_SERVER,
+          fmt::format("Coordinator has registered coordinator server on {} for instance {}.",
+                      coordinator_socket_address_tv.ValueString(), coordinator_query->instance_name_));
+      return callback;
+#endif
+    }
+    case CoordinatorQuery::Action::REGISTER_REPLICA_COORDINATOR_SERVER: {
+      if (!license::global_license_checker.IsEnterpriseValidFast()) {
+        throw QueryException("Trying to use enterprise feature without a valid license.");
+      }
+#ifdef MG_ENTERPRISE
+      if constexpr (!coordination::allow_ha) {
+        throw QueryRuntimeException(
+            "High availability is experimental feature. Please set MG_EXPERIMENTAL_HIGH_AVAILABILITY compile flag to "
+            "be able to use this functionality.");
+      }
+      if (!FLAGS_coordinator) {
+        throw QueryRuntimeException("Only coordinator can register coordinator server!");
+      }
+      // TODO: MemoryResource for EvaluationContext, it should probably be passed as
+      // the argument to Callback.
+      EvaluationContext evaluation_context{.timestamp = QueryTimestamp(), .parameters = parameters};
+      auto evaluator = PrimitiveLiteralExpressionEvaluator{evaluation_context};
+      auto coordinator_socket_address_tv = coordinator_query->coordinator_socket_address_->Accept(evaluator);
+      auto replication_socket_address_tv = coordinator_query->socket_address_->Accept(evaluator);
+      callback.fn = [handler = CoordQueryHandler{dbms_handler}, coordinator_socket_address_tv,
+                     replication_socket_address_tv, main_check_frequency = config.replication_replica_check_frequency,
+                     instance_name = coordinator_query->instance_name_,
+                     sync_mode = coordinator_query->sync_mode_]() mutable {
+        handler.RegisterReplicaCoordinatorServer(std::string(replication_socket_address_tv.ValueString()),
+                                                 std::string(coordinator_socket_address_tv.ValueString()),
+                                                 main_check_frequency, instance_name, sync_mode);
+        return std::vector<std::vector<TypedValue>>();
+      };
+
+      notifications->emplace_back(
+          SeverityLevel::INFO, NotificationCode::REGISTER_COORDINATOR_SERVER,
+          fmt::format("Coordinator has registered coordinator server on {} for instance {}.",
+                      coordinator_socket_address_tv.ValueString(), coordinator_query->instance_name_));
+      return callback;
+#endif
+    }
+    case CoordinatorQuery::Action::SHOW_REPLICATION_CLUSTER: {
+      if (!license::global_license_checker.IsEnterpriseValidFast()) {
+        throw QueryException("Trying to use enterprise feature without a valid license.");
+      }
+#ifdef MG_ENTERPRISE
+      if constexpr (!coordination::allow_ha) {
+        throw QueryRuntimeException(
+            "High availability is experimental feature. Please set MG_EXPERIMENTAL_HIGH_AVAILABILITY compile flag to "
+            "be able to use this functionality.");
+      }
+      if (!FLAGS_coordinator) {
+        throw QueryRuntimeException("Only coordinator can run SHOW REPLICATION CLUSTER.");
+      }
+
+      callback.header = {"name", "socket_address", "alive", "role"};
+      callback.fn = [handler = CoordQueryHandler{dbms_handler}, replica_nfields = callback.header.size()]() mutable {
+        const auto main = handler.ShowMainOnCoordinator();
+        const auto health_check_main = main ? handler.PingMainOnCoordinator() : std::nullopt;
+        const auto result_status = handler.ShowMainReplicaStatus(
+            handler.ShowReplicasOnCoordinator(), handler.PingReplicasOnCoordinator(), main, health_check_main);
+        std::vector<std::vector<TypedValue>> result{};
+        result.reserve(result_status.size());
+
+        std::ranges::transform(result_status, std::back_inserter(result),
+                               [](const auto &status) -> std::vector<TypedValue> {
+                                 return {TypedValue{status.name}, TypedValue{status.socket_address},
+                                         TypedValue{status.alive}, TypedValue{status.is_main ? "main" : "replica"}};
+                               });
+        return result;
+      };
+      return callback;
+#endif
+    }
+    case CoordinatorQuery::Action::DO_FAILOVER: {
+      if (!license::global_license_checker.IsEnterpriseValidFast()) {
+        throw QueryException("Trying to use enterprise feature without a valid license.");
+      }
+#ifdef MG_ENTERPRISE
+      if constexpr (!coordination::allow_ha) {
+        throw QueryRuntimeException(
+            "High availability is experimental feature. Please set MG_EXPERIMENTAL_HIGH_AVAILABILITY compile flag to "
+            "be able to use this functionality.");
+      }
+      if (!FLAGS_coordinator) {
+        throw QueryRuntimeException("Only coordinator can run DO FAILOVER!");
+      }
+
+      callback.header = {"name", "socket_address", "alive", "role"};
+      callback.fn = [handler = CoordQueryHandler{dbms_handler}]() mutable {
+        handler.DoFailover();
+        const auto main = handler.ShowMainOnCoordinator();
+        const auto health_check_main = main ? handler.PingMainOnCoordinator() : std::nullopt;
+        const auto result_status = handler.ShowMainReplicaStatus(
+            handler.ShowReplicasOnCoordinator(), handler.PingReplicasOnCoordinator(), main, health_check_main);
+        std::vector<std::vector<TypedValue>> result{};
+        result.reserve(result_status.size());
+
+        std::ranges::transform(result_status, std::back_inserter(result),
+                               [](const auto &status) -> std::vector<TypedValue> {
+                                 return {TypedValue{status.name}, TypedValue{status.socket_address},
+                                         TypedValue{status.alive}, TypedValue{status.is_main ? "main" : "replica"}};
+                               });
+        return result;
+      };
+      notifications->emplace_back(SeverityLevel::INFO, NotificationCode::DO_FAILOVER,
+                                  "DO FAILOVER called on coordinator.");
+      return callback;
+#endif
+    }
+      return callback;
+  }
+}
+
 stream::CommonStreamInfo GetCommonStreamInfo(StreamQuery *stream_query, ExpressionVisitor<TypedValue> &evaluator) {
   return {
       .batch_interval = GetOptionalValue<std::chrono::milliseconds>(stream_query->batch_interval_, evaluator)
@@ -2293,6 +2628,34 @@ PreparedQuery PrepareReplicationQuery(ParsedQuery parsed_query, bool in_explicit
   // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks)
 }
 
+PreparedQuery PrepareCoordinatorQuery(ParsedQuery parsed_query, bool in_explicit_transaction,
+                                      std::vector<Notification> *notifications, dbms::DbmsHandler &dbms_handler,
+                                      const InterpreterConfig &config) {
+  if (in_explicit_transaction) {
+    throw CoordinatorModificationInMulticommandTxException();
+  }
+
+  auto *coordinator_query = utils::Downcast<CoordinatorQuery>(parsed_query.query);
+  auto callback =
+      HandleCoordinatorQuery(coordinator_query, parsed_query.parameters, &dbms_handler, config, notifications);
+
+  return PreparedQuery{callback.header, std::move(parsed_query.required_privileges),
+                       [callback_fn = std::move(callback.fn), pull_plan = std::shared_ptr<PullPlanVector>{nullptr}](
+                           AnyStream *stream, std::optional<int> n) mutable -> std::optional<QueryHandlerResult> {
+                         if (UNLIKELY(!pull_plan)) {
+                           pull_plan = std::make_shared<PullPlanVector>(callback_fn());
+                         }
+
+                         if (pull_plan->Pull(stream, n)) [[likely]] {
+                           return QueryHandlerResult::COMMIT;
+                         }
+                         return std::nullopt;
+                       },
+                       RWType::NONE};
+  // False positive report for the std::make_shared above
+  // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks)
+}
+
 PreparedQuery PrepareLockPathQuery(ParsedQuery parsed_query, bool in_explicit_transaction, CurrentDB &current_db) {
   if (in_explicit_transaction) {
     throw LockPathModificationInMulticommandTxException();
@@ -3795,6 +4158,13 @@ Interpreter::PrepareResult Interpreter::Prepare(const std::string &query_string,
       SetupDatabaseTransaction(could_commit, unique);
     }
 
+#ifdef MG_ENTERPRISE
+    if (FLAGS_coordinator && !utils::Downcast<CoordinatorQuery>(parsed_query.query) &&
+        !utils::Downcast<SettingQuery>(parsed_query.query)) {
+      throw QueryRuntimeException("Coordinator can run only coordinator queries!");
+    }
+#endif
+
     utils::Timer planning_timer;
     PreparedQuery prepared_query;
     utils::MemoryResource *memory_resource =
@@ -3837,6 +4207,10 @@ Interpreter::PrepareResult Interpreter::Prepare(const std::string &query_string,
       prepared_query =
           PrepareReplicationQuery(std::move(parsed_query), in_explicit_transaction_, &query_execution->notifications,
                                   *interpreter_context_->dbms_handler, current_db_, interpreter_context_->config);
+    } else if (utils::Downcast<CoordinatorQuery>(parsed_query.query)) {
+      prepared_query =
+          PrepareCoordinatorQuery(std::move(parsed_query), in_explicit_transaction_, &query_execution->notifications,
+                                  *interpreter_context_->dbms_handler, interpreter_context_->config);
     } else if (utils::Downcast<LockPathQuery>(parsed_query.query)) {
       prepared_query = PrepareLockPathQuery(std::move(parsed_query), in_explicit_transaction_, current_db_);
     } else if (utils::Downcast<FreeMemoryQuery>(parsed_query.query)) {

src/query/interpreter.hpp

@@ -15,6 +15,7 @@
 
 #include <gflags/gflags.h>
 
+#include "coordination/coordinator_entity_info.hpp"
 #include "dbms/database.hpp"
 #include "dbms/dbms_handler.hpp"
 #include "memory/query_memory_control.hpp"
@@ -68,6 +69,75 @@ inline constexpr size_t kExecutionPoolMaxBlockSize = 1024UL;  // 2 ^ 10
 
 enum class QueryHandlerResult { COMMIT, ABORT, NOTHING };
 
+class CoordinatorQueryHandler {
+ public:
+  CoordinatorQueryHandler() = default;
+  virtual ~CoordinatorQueryHandler() = default;
+
+  CoordinatorQueryHandler(const CoordinatorQueryHandler &) = default;
+  CoordinatorQueryHandler &operator=(const CoordinatorQueryHandler &) = default;
+
+  CoordinatorQueryHandler(CoordinatorQueryHandler &&) = default;
+  CoordinatorQueryHandler &operator=(CoordinatorQueryHandler &&) = default;
+
+  struct Replica {
+    std::string name;
+    std::string socket_address;
+    ReplicationQuery::SyncMode sync_mode;
+    std::optional<double> timeout;
+    uint64_t current_timestamp_of_replica;
+    uint64_t current_number_of_timestamp_behind_master;
+    ReplicationQuery::ReplicaState state;
+  };
+
+#ifdef MG_ENTERPRISE
+  struct MainReplicaStatus {
+    std::string_view name;
+    std::string socket_address;
+    bool alive;
+    bool is_main;
+
+    MainReplicaStatus(std::string_view name, std::string socket_address, bool alive, bool is_main)
+        : name{name}, socket_address{std::move(socket_address)}, alive{alive}, is_main{is_main} {}
+  };
+#endif
+
+#ifdef MG_ENTERPRISE
+  /// @throw QueryRuntimeException if an error ocurred.
+  virtual void RegisterReplicaCoordinatorServer(const std::string &replication_socket_address,
+                                                const std::string &coordinator_socket_address,
+                                                const std::chrono::seconds instance_check_frequency,
+                                                const std::string &instance_name,
+                                                CoordinatorQuery::SyncMode sync_mode) = 0;
+  virtual void RegisterMainCoordinatorServer(const std::string &socket_address,
+                                             const std::chrono::seconds instance_check_frequency,
+                                             const std::string &instance_name) = 0;
+
+  /// @throw QueryRuntimeException if an error ocurred.
+  virtual std::vector<coordination::CoordinatorEntityInfo> ShowReplicasOnCoordinator() const = 0;
+
+  /// @throw QueryRuntimeException if an error ocurred.
+  virtual std::optional<coordination::CoordinatorEntityInfo> ShowMainOnCoordinator() const = 0;
+
+  /// @throw QueryRuntimeException if an error ocurred.
+  virtual std::unordered_map<std::string_view, bool> PingReplicasOnCoordinator() const = 0;
+
+  /// @throw QueryRuntimeException if an error ocurred.
+  virtual std::optional<coordination::CoordinatorEntityHealthInfo> PingMainOnCoordinator() const = 0;
+
+  /// @throw QueryRuntimeException if an error ocurred.
+  virtual void DoFailover() const = 0;
+
+  /// @throw QueryRuntimeException if an error ocurred.
+  virtual std::vector<MainReplicaStatus> ShowMainReplicaStatus(
+      const std::vector<coordination::CoordinatorEntityInfo> &replicas,
+      const std::unordered_map<std::string_view, bool> &health_check_replicas,
+      const std::optional<coordination::CoordinatorEntityInfo> &main,
+      const std::optional<coordination::CoordinatorEntityHealthInfo> &health_check_main) const = 0;
+
+#endif
+};
+
 class AnalyzeGraphQueryHandler {
  public:
   AnalyzeGraphQueryHandler() = default;

src/query/metadata.cpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -66,6 +66,12 @@ constexpr std::string_view GetCodeString(const NotificationCode code) {
       return "PlanHinting"sv;
     case NotificationCode::REGISTER_REPLICA:
       return "RegisterReplica"sv;
+#ifdef MG_ENTERPRISE
+    case NotificationCode::REGISTER_COORDINATOR_SERVER:
+      return "RegisterCoordinatorServer"sv;
+    case NotificationCode::DO_FAILOVER:
+      return "DoFailover"sv;
+#endif
     case NotificationCode::REPLICA_PORT_WARNING:
       return "ReplicaPortWarning"sv;
     case NotificationCode::SET_REPLICA:

src/query/metadata.hpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -42,6 +42,10 @@ enum class NotificationCode : uint8_t {
   PLAN_HINTING,
   REPLICA_PORT_WARNING,
   REGISTER_REPLICA,
+#ifdef MG_ENTERPRISE
+  REGISTER_COORDINATOR_SERVER,
+  DO_FAILOVER,
+#endif
   SET_REPLICA,
   START_STREAM,
   START_ALL_STREAMS,

src/replication/CMakeLists.txt

@@ -5,10 +5,9 @@ target_sources(mg-replication
         include/replication/state.hpp
         include/replication/epoch.hpp
         include/replication/config.hpp
-        include/replication/mode.hpp
-        include/replication/messages.hpp
         include/replication/role.hpp
         include/replication/status.hpp
+        include/replication/messages.hpp
         include/replication/replication_client.hpp
         include/replication/replication_server.hpp
 
@@ -25,6 +24,6 @@ target_include_directories(mg-replication PUBLIC include)
 
 find_package(fmt REQUIRED)
 target_link_libraries(mg-replication
-    PUBLIC mg::utils mg::kvstore lib::json mg::rpc mg::slk
+    PUBLIC mg::utils mg::kvstore lib::json mg::rpc mg::slk mg::io mg::repl_coord_glue
     PRIVATE fmt::fmt
 )

src/replication/include/replication/config.hpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -15,7 +15,7 @@
 #include <cstdint>
 #include <optional>
 #include <string>
-#include "replication/mode.hpp"
+#include "replication_coordination_glue/mode.hpp"
 
 namespace memgraph::replication {
 
@@ -24,7 +24,7 @@ inline constexpr auto *kDefaultReplicationServerIp = "0.0.0.0";
 
 struct ReplicationClientConfig {
   std::string name;
-  ReplicationMode mode{};
+  replication_coordination_glue::ReplicationMode mode{};
   std::string ip_address;
   uint16_t port{};
 

src/replication/include/replication/messages.hpp

@@ -15,27 +15,6 @@
 #include "slk/serialization.hpp"
 
 namespace memgraph::replication {
-
-struct FrequentHeartbeatReq {
-  static const utils::TypeInfo kType;                            // TODO: make constexpr?
-  static const utils::TypeInfo &GetTypeInfo() { return kType; }  // WHAT?
-
-  static void Load(FrequentHeartbeatReq *self, memgraph::slk::Reader *reader);
-  static void Save(const FrequentHeartbeatReq &self, memgraph::slk::Builder *builder);
-  FrequentHeartbeatReq() = default;
-};
-
-struct FrequentHeartbeatRes {
-  static const utils::TypeInfo kType;
-  static const utils::TypeInfo &GetTypeInfo() { return kType; }
-
-  static void Load(FrequentHeartbeatRes *self, memgraph::slk::Reader *reader);
-  static void Save(const FrequentHeartbeatRes &self, memgraph::slk::Builder *builder);
-  FrequentHeartbeatRes() = default;
-};
-
-using FrequentHeartbeatRpc = rpc::RequestResponse<FrequentHeartbeatReq, FrequentHeartbeatRes>;
-
 struct SystemHeartbeatReq {
   static const utils::TypeInfo kType;
   static const utils::TypeInfo &GetTypeInfo() { return kType; }
@@ -58,16 +37,9 @@ struct SystemHeartbeatRes {
 };
 
 using SystemHeartbeatRpc = rpc::RequestResponse<SystemHeartbeatReq, SystemHeartbeatRes>;
-
-void FrequentHeartbeatHandler(slk::Reader *req_reader, slk::Builder *res_builder);
-
 }  // namespace memgraph::replication
 
 namespace memgraph::slk {
-void Save(const memgraph::replication::FrequentHeartbeatRes &self, memgraph::slk::Builder *builder);
-void Load(memgraph::replication::FrequentHeartbeatRes *self, memgraph::slk::Reader *reader);
-void Save(const memgraph::replication::FrequentHeartbeatReq & /*self*/, memgraph::slk::Builder * /*builder*/);
-void Load(memgraph::replication::FrequentHeartbeatReq * /*self*/, memgraph::slk::Reader * /*reader*/);
 void Save(const memgraph::replication::SystemHeartbeatRes &self, memgraph::slk::Builder *builder);
 void Load(memgraph::replication::SystemHeartbeatRes *self, memgraph::slk::Reader *reader);
 void Save(const memgraph::replication::SystemHeartbeatReq & /*self*/, memgraph::slk::Builder * /*builder*/);

src/replication/include/replication/replication_client.hpp

@@ -12,7 +12,7 @@
 #pragma once
 
 #include "replication/config.hpp"
-#include "replication/messages.hpp"
+#include "replication_coordination_glue/messages.hpp"
 #include "rpc/client.hpp"
 #include "utils/scheduler.hpp"
 #include "utils/synchronized.hpp"
@@ -45,7 +45,7 @@ struct ReplicationClient {
                            [this, cb = std::forward<F>(callback), reconnect = false]() mutable {
                              try {
                                {
-                                 auto stream{rpc_client_.Stream<memgraph::replication::FrequentHeartbeatRpc>()};
+                                 auto stream{rpc_client_.Stream<memgraph::replication_coordination_glue::FrequentHeartbeatRpc>()};
                                  stream.AwaitResponse();
                                }
                                cb(reconnect, *this);
@@ -73,7 +73,7 @@ struct ReplicationClient {
   };
   utils::Synchronized<State> state_{State::BEHIND};
 
-  memgraph::replication::ReplicationMode mode_{memgraph::replication::ReplicationMode::SYNC};
+  replication_coordination_glue::ReplicationMode mode_{replication_coordination_glue::ReplicationMode::SYNC};
   // This thread pool is used for background tasks so we don't
   // block the main storage thread
   // We use only 1 thread for 2 reasons:

src/replication/include/replication/state.hpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -14,9 +14,9 @@
 #include "kvstore/kvstore.hpp"
 #include "replication/config.hpp"
 #include "replication/epoch.hpp"
-#include "replication/mode.hpp"
 #include "replication/replication_client.hpp"
 #include "replication/role.hpp"
+#include "replication_coordination_glue/mode.hpp"
 #include "replication_server.hpp"
 #include "status.hpp"
 #include "utils/result.hpp"

src/replication/include/replication/status.hpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -42,7 +42,7 @@ struct MainRole {
 
 // fragment of key: "__replication_role"
 struct ReplicaRole {
-  ReplicationServerConfig config;
+  ReplicationServerConfig config{};
   friend bool operator==(ReplicaRole const &, ReplicaRole const &) = default;
 };
 

src/replication/messages.cpp

@@ -8,25 +8,32 @@
 // the Business Source License, use of this software will be governed
 // by the Apache License, Version 2.0, included in the file
 // licenses/APL.txt.
-
 #include "replication/messages.hpp"
-#include "rpc/messages.hpp"
+
-#include "slk/serialization.hpp"
+namespace memgraph::replication {
-#include "slk/streams.hpp"
+
+constexpr utils::TypeInfo SystemHeartbeatReq::kType{utils::TypeId::REP_SYSTEM_HEARTBEAT_REQ, "SystemHeartbeatReq",
+                                                    nullptr};
+
+constexpr utils::TypeInfo SystemHeartbeatRes::kType{utils::TypeId::REP_SYSTEM_HEARTBEAT_RES, "SystemHeartbeatRes",
+                                                    nullptr};
+
+void SystemHeartbeatReq::Save(const SystemHeartbeatReq &self, memgraph::slk::Builder *builder) {
+  memgraph::slk::Save(self, builder);
+}
+void SystemHeartbeatReq::Load(SystemHeartbeatReq *self, memgraph::slk::Reader *reader) {
+  memgraph::slk::Load(self, reader);
+}
+void SystemHeartbeatRes::Save(const SystemHeartbeatRes &self, memgraph::slk::Builder *builder) {
+  memgraph::slk::Save(self, builder);
+}
+void SystemHeartbeatRes::Load(SystemHeartbeatRes *self, memgraph::slk::Reader *reader) {
+  memgraph::slk::Load(self, reader);
+}
+
+}  // namespace memgraph::replication
 
 namespace memgraph::slk {
-// Serialize code for FrequentHeartbeatRes
-void Save(const memgraph::replication::FrequentHeartbeatRes &self, memgraph::slk::Builder *builder) {}
-void Load(memgraph::replication::FrequentHeartbeatRes *self, memgraph::slk::Reader *reader) {}
-
-// Serialize code for FrequentHeartbeatReq
-void Save(const memgraph::replication::FrequentHeartbeatReq & /*self*/, memgraph::slk::Builder * /*builder*/) {
-  /* Nothing to serialize */
-}
-void Load(memgraph::replication::FrequentHeartbeatReq * /*self*/, memgraph::slk::Reader * /*reader*/) {
-  /* Nothing to serialize */
-}
-
 // Serialize code for SystemHeartbeatRes
 void Save(const memgraph::replication::SystemHeartbeatRes &self, memgraph::slk::Builder *builder) {
   memgraph::slk::Save(self.system_timestamp, builder);
@@ -42,55 +49,4 @@ void Save(const memgraph::replication::SystemHeartbeatReq & /*self*/, memgraph::
 void Load(memgraph::replication::SystemHeartbeatReq * /*self*/, memgraph::slk::Reader * /*reader*/) {
   /* Nothing to serialize */
 }
-
 }  // namespace memgraph::slk
-
-namespace memgraph::replication {
-
-constexpr utils::TypeInfo FrequentHeartbeatReq::kType{utils::TypeId::REP_FREQUENT_HEARTBEAT_REQ, "FrequentHeartbeatReq",
-                                                      nullptr};
-
-constexpr utils::TypeInfo FrequentHeartbeatRes::kType{utils::TypeId::REP_FREQUENT_HEARTBEAT_RES, "FrequentHeartbeatRes",
-                                                      nullptr};
-
-constexpr utils::TypeInfo SystemHeartbeatReq::kType{utils::TypeId::REP_SYSTEM_HEARTBEAT_REQ, "SystemHeartbeatReq",
-                                                    nullptr};
-
-constexpr utils::TypeInfo SystemHeartbeatRes::kType{utils::TypeId::REP_SYSTEM_HEARTBEAT_RES, "SystemHeartbeatRes",
-                                                    nullptr};
-
-void FrequentHeartbeatReq::Save(const FrequentHeartbeatReq &self, memgraph::slk::Builder *builder) {
-  memgraph::slk::Save(self, builder);
-}
-void FrequentHeartbeatReq::Load(FrequentHeartbeatReq *self, memgraph::slk::Reader *reader) {
-  memgraph::slk::Load(self, reader);
-}
-void FrequentHeartbeatRes::Save(const FrequentHeartbeatRes &self, memgraph::slk::Builder *builder) {
-  memgraph::slk::Save(self, builder);
-}
-void FrequentHeartbeatRes::Load(FrequentHeartbeatRes *self, memgraph::slk::Reader *reader) {
-  memgraph::slk::Load(self, reader);
-}
-
-void SystemHeartbeatReq::Save(const SystemHeartbeatReq &self, memgraph::slk::Builder *builder) {
-  memgraph::slk::Save(self, builder);
-}
-void SystemHeartbeatReq::Load(SystemHeartbeatReq *self, memgraph::slk::Reader *reader) {
-  memgraph::slk::Load(self, reader);
-}
-void SystemHeartbeatRes::Save(const SystemHeartbeatRes &self, memgraph::slk::Builder *builder) {
-  memgraph::slk::Save(self, builder);
-}
-void SystemHeartbeatRes::Load(SystemHeartbeatRes *self, memgraph::slk::Reader *reader) {
-  memgraph::slk::Load(self, reader);
-}
-
-void FrequentHeartbeatHandler(slk::Reader *req_reader, slk::Builder *res_builder) {
-  FrequentHeartbeatReq req;
-  FrequentHeartbeatReq::Load(&req, req_reader);
-  memgraph::slk::Load(&req, req_reader);
-  FrequentHeartbeatRes res{};
-  memgraph::slk::Save(res, res_builder);
-}
-
-}  // namespace memgraph::replication

src/replication/replication_client.cpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -28,8 +28,8 @@ ReplicationClient::ReplicationClient(const memgraph::replication::ReplicationCli
       mode_{config.mode} {}
 
 ReplicationClient::~ReplicationClient() {
-  auto endpoint = rpc_client_.Endpoint();
   try {
+    auto const &endpoint = rpc_client_.Endpoint();
     spdlog::trace("Closing replication client on {}:{}", endpoint.address, endpoint.port);
   } catch (...) {
     // Logging can throw. Not a big deal, just ignore.

src/replication/replication_server.cpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -10,7 +10,7 @@
 // licenses/APL.txt.
 
 #include "replication/replication_server.hpp"
-#include "replication/messages.hpp"
+#include "replication_coordination_glue/messages.hpp"
 
 namespace memgraph::replication {
 namespace {
@@ -32,9 +32,9 @@ ReplicationServer::ReplicationServer(const memgraph::replication::ReplicationSer
     : rpc_server_context_{CreateServerContext(config)},
       rpc_server_{io::network::Endpoint{config.ip_address, config.port}, &rpc_server_context_,
                   kReplicationServerThreads} {
-  rpc_server_.Register<FrequentHeartbeatRpc>([](auto *req_reader, auto *res_builder) {
+  rpc_server_.Register<replication_coordination_glue::FrequentHeartbeatRpc>([](auto *req_reader, auto *res_builder) {
     spdlog::debug("Received FrequentHeartbeatRpc");
-    FrequentHeartbeatHandler(req_reader, res_builder);
+    replication_coordination_glue::FrequentHeartbeatHandler(req_reader, res_builder);
   });
 }
 

src/replication/state.cpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -219,10 +219,12 @@ bool ReplicationState::TryPersistRegisteredReplica(const ReplicationClientConfig
 
 bool ReplicationState::SetReplicationRoleMain() {
   auto new_epoch = utils::GenerateUUID();
+
   if (!TryPersistRoleMain(new_epoch)) {
     return false;
   }
   replication_data_ = RoleMainData{ReplicationEpoch{new_epoch}};
+
   return true;
 }
 
@@ -237,6 +239,7 @@ bool ReplicationState::SetReplicationRoleReplica(const ReplicationServerConfig &
 utils::BasicResult<RegisterReplicaError, ReplicationClient *> ReplicationState::RegisterReplica(
     const ReplicationClientConfig &config) {
   auto const replica_handler = [](RoleReplicaData const &) { return RegisterReplicaError::NOT_MAIN; };
+
   ReplicationClient *client{nullptr};
   auto const main_handler = [&client, &config, this](RoleMainData &mainData) -> RegisterReplicaError {
     // name check

src/replication/status.cpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -95,7 +95,7 @@ void from_json(const nlohmann::json &j, ReplicationReplicaEntry &p) {
   auto seconds = j.at(kCheckFrequency).get<std::chrono::seconds::rep>();
   auto config = ReplicationClientConfig{
       .name = j.at(kReplicaName).get<std::string>(),
-      .mode = j.at(kSyncMode).get<ReplicationMode>(),
+      .mode = j.at(kSyncMode).get<replication_coordination_glue::ReplicationMode>(),
       .ip_address = j.at(kIpAddress).get<std::string>(),
       .port = j.at(kPort).get<uint16_t>(),
       .replica_check_frequency = std::chrono::seconds{seconds},

src/replication_coordination_glue/CMakeLists.txt

@@ -0,0 +1,13 @@
+add_library(mg-repl_coord_glue STATIC )
+add_library(mg::repl_coord_glue ALIAS mg-repl_coord_glue)
+
+target_sources(mg-repl_coord_glue
+        PUBLIC
+        messages.hpp
+        mode.hpp
+
+        PRIVATE
+        messages.cpp
+)
+
+target_link_libraries(mg-repl_coord_glue mg-rpc mg-slk)

src/replication_coordination_glue/messages.cpp

@@ -0,0 +1,63 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#include "replication_coordination_glue/messages.hpp"
+#include "rpc/messages.hpp"
+#include "slk/serialization.hpp"
+#include "slk/streams.hpp"
+
+namespace memgraph::slk {
+// Serialize code for FrequentHeartbeatRes
+void Save(const memgraph::replication_coordination_glue::FrequentHeartbeatRes &self, memgraph::slk::Builder *builder) {}
+void Load(memgraph::replication_coordination_glue::FrequentHeartbeatRes *self, memgraph::slk::Reader *reader) {}
+
+// Serialize code for FrequentHeartbeatReq
+void Save(const memgraph::replication_coordination_glue::FrequentHeartbeatReq & /*self*/,
+          memgraph::slk::Builder * /*builder*/) {
+  /* Nothing to serialize */
+}
+void Load(memgraph::replication_coordination_glue::FrequentHeartbeatReq * /*self*/,
+          memgraph::slk::Reader * /*reader*/) {
+  /* Nothing to serialize */
+}
+
+}  // namespace memgraph::slk
+
+namespace memgraph::replication_coordination_glue {
+
+constexpr utils::TypeInfo FrequentHeartbeatReq::kType{utils::TypeId::REP_FREQUENT_HEARTBEAT_REQ, "FrequentHeartbeatReq",
+                                                      nullptr};
+
+constexpr utils::TypeInfo FrequentHeartbeatRes::kType{utils::TypeId::REP_FREQUENT_HEARTBEAT_RES, "FrequentHeartbeatRes",
+                                                      nullptr};
+
+void FrequentHeartbeatReq::Save(const FrequentHeartbeatReq &self, memgraph::slk::Builder *builder) {
+  memgraph::slk::Save(self, builder);
+}
+void FrequentHeartbeatReq::Load(FrequentHeartbeatReq *self, memgraph::slk::Reader *reader) {
+  memgraph::slk::Load(self, reader);
+}
+void FrequentHeartbeatRes::Save(const FrequentHeartbeatRes &self, memgraph::slk::Builder *builder) {
+  memgraph::slk::Save(self, builder);
+}
+void FrequentHeartbeatRes::Load(FrequentHeartbeatRes *self, memgraph::slk::Reader *reader) {
+  memgraph::slk::Load(self, reader);
+}
+
+void FrequentHeartbeatHandler(slk::Reader *req_reader, slk::Builder *res_builder) {
+  FrequentHeartbeatReq req;
+  FrequentHeartbeatReq::Load(&req, req_reader);
+  memgraph::slk::Load(&req, req_reader);
+  FrequentHeartbeatRes res{};
+  memgraph::slk::Save(res, res_builder);
+}
+
+}  // namespace memgraph::replication_coordination_glue

src/replication_coordination_glue/messages.hpp

@@ -0,0 +1,49 @@
+// Copyright 2024 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include "rpc/messages.hpp"
+#include "slk/serialization.hpp"
+
+namespace memgraph::replication_coordination_glue {
+
+struct FrequentHeartbeatReq {
+  static const utils::TypeInfo kType;  // TODO: make constexpr?
+  static const utils::TypeInfo &GetTypeInfo() { return kType; }
+
+  static void Load(FrequentHeartbeatReq *self, memgraph::slk::Reader *reader);
+  static void Save(const FrequentHeartbeatReq &self, memgraph::slk::Builder *builder);
+  FrequentHeartbeatReq() = default;
+};
+
+struct FrequentHeartbeatRes {
+  static const utils::TypeInfo kType;
+  static const utils::TypeInfo &GetTypeInfo() { return kType; }
+
+  static void Load(FrequentHeartbeatRes *self, memgraph::slk::Reader *reader);
+  static void Save(const FrequentHeartbeatRes &self, memgraph::slk::Builder *builder);
+  FrequentHeartbeatRes() = default;
+};
+
+using FrequentHeartbeatRpc = rpc::RequestResponse<FrequentHeartbeatReq, FrequentHeartbeatRes>;
+
+void FrequentHeartbeatHandler(slk::Reader *req_reader, slk::Builder *res_builder);
+
+}  // namespace memgraph::replication_coordination_glue
+
+namespace memgraph::slk {
+void Save(const memgraph::replication_coordination_glue::FrequentHeartbeatRes &self, memgraph::slk::Builder *builder);
+void Load(memgraph::replication_coordination_glue::FrequentHeartbeatRes *self, memgraph::slk::Reader *reader);
+void Save(const memgraph::replication_coordination_glue::FrequentHeartbeatReq & /*self*/,
+          memgraph::slk::Builder * /*builder*/);
+void Load(memgraph::replication_coordination_glue::FrequentHeartbeatReq * /*self*/, memgraph::slk::Reader * /*reader*/);
+}  // namespace memgraph::slk

src/replication_coordination_glue/mode.hpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -10,7 +10,9 @@
 // licenses/APL.txt.
 
 #pragma once
+
 #include <cstdint>
-namespace memgraph::replication {
+
+namespace memgraph::replication_coordination_glue {
 enum class ReplicationMode : std::uint8_t { SYNC, ASYNC };
-}
+}  // namespace memgraph::replication_coordination_glue

src/slk/serialization.hpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -55,6 +55,12 @@ class SlkDecodeException : public utils::BasicException {
 // here because C++ doesn't know how to resolve the function call if it isn't in
 // the global namespace.
 
+template <typename T>
+inline void Save(const std::vector<T> &obj, Builder *builder,
+                 std::function<void(const T &, Builder *)> item_save_function);
+template <typename T>
+inline void Load(std::vector<T> *obj, Reader *reader, std::function<void(T *, Reader *)> item_load_function);
+
 template <typename T>
 void Save(const std::vector<T> &obj, Builder *builder);
 template <typename T>
@@ -509,4 +515,17 @@ inline void Load(utils::TypeId *obj, Reader *reader) {
   *obj = utils::TypeId(utils::MemcpyCast<enum_type>(obj_encoded));
 }
 
+template <utils::Enum T>
+void Save(const T &enum_value, slk::Builder *builder) {
+  slk::Save(utils::UnderlyingCast(enum_value), builder);
+}
+
+template <utils::Enum T>
+void Load(T *enum_value, slk::Reader *reader) {
+  using UnderlyingType = std::underlying_type_t<T>;
+  UnderlyingType value;
+  slk::Load(&value, reader);
+  *enum_value = static_cast<T>(value);
+}
+
 }  // namespace memgraph::slk

src/storage/v2/property_store.cpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -1050,14 +1050,11 @@ bool PropertyStore::HasProperty(PropertyId property) const {
   return ExistsSpecificProperty(&reader, property) == ExpectedPropertyStatus::EQUAL;
 }
 
-/// TODO: andi write a unit test for it
 bool PropertyStore::HasAllProperties(const std::set<PropertyId> &properties) const {
   return std::all_of(properties.begin(), properties.end(), [this](const auto &prop) { return HasProperty(prop); });
 }
 
-/// TODO: andi write a unit test for it
 bool PropertyStore::HasAllPropertyValues(const std::vector<PropertyValue> &property_values) const {
-  /// TODO: andi extract this into a private method
   auto property_map = Properties();
   std::vector<PropertyValue> all_property_values;
   transform(property_map.begin(), property_map.end(), back_inserter(all_property_values),

src/storage/v2/property_store.hpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -55,7 +55,6 @@ class PropertyStore {
 
   /// Checks whether all property values in the vector `property_values` exist in the store. The time
   /// complexity of this function is O(n^2).
-  /// TODO: andi Not so sure it is quadratic complexity
   bool HasAllPropertyValues(const std::vector<PropertyValue> &property_values) const;
 
   /// Extracts property values for all property ids in the set `properties`. The time

src/storage/v2/replication/global.hpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -31,7 +31,7 @@ struct TimestampInfo {
 
 struct ReplicaInfo {
   std::string name;
-  memgraph::replication::ReplicationMode mode;
+  replication_coordination_glue::ReplicationMode mode;
   io::network::Endpoint endpoint;
   replication::ReplicaState state;
   TimestampInfo timestamp_info;

src/storage/v2/replication/replication_client.cpp

@@ -226,7 +226,7 @@ bool ReplicationStorageClient::FinalizeTransactionReplication(Storage *storage,
     }
   };
 
-  if (client_.mode_ == memgraph::replication::ReplicationMode::ASYNC) {
+  if (client_.mode_ == replication_coordination_glue::ReplicationMode::ASYNC) {
     client_.thread_pool_.AddTask([task = std::move(task)]() mutable { (void)task(); });
     return true;
   }

src/storage/v2/replication/replication_client.hpp

@@ -13,8 +13,8 @@
 
 #include "replication/config.hpp"
 #include "replication/epoch.hpp"
-#include "replication/messages.hpp"
 #include "replication/replication_client.hpp"
+#include "replication_coordination_glue/messages.hpp"
 #include "rpc/client.hpp"
 #include "storage/v2/database_access.hpp"
 #include "storage/v2/durability/storage_global_operation.hpp"
@@ -94,7 +94,7 @@ class ReplicationStorageClient {
   ~ReplicationStorageClient() = default;
 
   // TODO Remove the client related functions
-  auto Mode() const -> memgraph::replication::ReplicationMode { return client_.mode_; }
+  auto Mode() const -> memgraph::replication_coordination_glue::ReplicationMode { return client_.mode_; }
   auto Name() const -> std::string const & { return client_.name_; }
   auto Endpoint() const -> io::network::Endpoint const & { return client_.rpc_client_.Endpoint(); }
 

src/storage/v2/replication/replication_storage_state.cpp

@@ -64,7 +64,7 @@ bool ReplicationStorageState::FinalizeTransaction(uint64_t timestamp, Storage *s
       client->IfStreamingTransaction([&](auto &stream) { stream.AppendTransactionEnd(timestamp); });
       const auto finalized = client->FinalizeTransactionReplication(storage, std::move(db_acc));
 
-      if (client->Mode() == memgraph::replication::ReplicationMode::SYNC) {
+      if (client->Mode() == replication_coordination_glue::ReplicationMode::SYNC) {
         finalized_on_all_replicas = finalized && finalized_on_all_replicas;
       }
     }

src/storage/v2/replication/slk.hpp

@@ -1,4 +1,4 @@
-// Copyright 2022 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -25,17 +25,4 @@ void Load(storage::Gid *gid, slk::Reader *reader);
 void Save(const storage::PropertyValue &value, slk::Builder *builder);
 void Load(storage::PropertyValue *value, slk::Reader *reader);
 
-template <utils::Enum T>
-void Save(const T &enum_value, slk::Builder *builder) {
-  slk::Save(utils::UnderlyingCast(enum_value), builder);
-}
-
-template <utils::Enum T>
-void Load(T *enum_value, slk::Reader *reader) {
-  using UnderlyingType = std::underlying_type_t<T>;
-  UnderlyingType value;
-  slk::Load(&value, reader);
-  *enum_value = static_cast<T>(value);
-}
-
 }  // namespace memgraph::slk

src/utils/typeinfo.hpp

@@ -94,6 +94,10 @@ enum class TypeId : uint64_t {
   REP_SYSTEM_RECOVERY_REQ,
   REP_SYSTEM_RECOVERY_RES,
 
+  // Coordinator
+  COORD_FAILOVER_REQ,
+  COORD_FAILOVER_RES,
+
   // AST
   AST_LABELIX = 3000,
   AST_PROPERTYIX,
@@ -201,6 +205,7 @@ enum class TypeId : uint64_t {
   AST_SHOW_DATABASES,
   AST_EDGE_IMPORT_MODE_QUERY,
   AST_PATTERN_COMPREHENSION,
+  AST_COORDINATOR_QUERY,
 
   // Symbol
   SYMBOL = 4000,

tests/e2e/CMakeLists.txt

@@ -77,8 +77,13 @@ add_subdirectory(query_modules_storage_modes)
 add_subdirectory(garbage_collection)
 add_subdirectory(query_planning)
 
+if (MG_EXPERIMENTAL_HIGH_AVAILABILITY)
+  add_subdirectory(high_availability_experimental)
+endif ()
+
+
 if (MG_EXPERIMENTAL_REPLICATION_MULTITENANCY)
-        add_subdirectory(replication_experimental)
+  add_subdirectory(replication_experimental)
 endif ()
 
 copy_e2e_python_files(pytest_runner pytest_runner.sh "")

tests/e2e/configuration/default_config.py

@@ -66,6 +66,8 @@ startup_config_dict = {
         "Time in seconds after which inactive Bolt sessions will be closed.",
     ),
     "cartesian_product_enabled": ("true", "true", "Enable cartesian product expansion."),
+    "coordinator": ("false", "false", "Controls whether the instance is a replication coordinator."),
+    "coordinator_server_port": ("0", "0", "Port on which coordinator servers will be started."),
     "data_directory": ("mg_data", "mg_data", "Path to directory in which to save all permanent data."),
     "data_recovery_on_startup": (
         "false",

tests/e2e/configuration/storage_info.py

@@ -11,7 +11,6 @@
 
 import sys
 
-import default_config
 import mgclient
 import pytest
 

tests/e2e/high_availability_experimental/CMakeLists.txt

@@ -0,0 +1,12 @@
+find_package(gflags REQUIRED)
+
+copy_e2e_python_files(ha_experimental coordinator.py)
+copy_e2e_python_files(ha_experimental client_initiated_failover.py)
+copy_e2e_python_files(ha_experimental uninitialized_cluster.py)
+copy_e2e_python_files(ha_experimental common.py)
+copy_e2e_python_files(ha_experimental conftest.py)
+copy_e2e_python_files(ha_experimental workloads.yaml)
+
+copy_e2e_python_files_from_parent_folder(ha_experimental ".." memgraph.py)
+copy_e2e_python_files_from_parent_folder(ha_experimental ".." interactive_mg_runner.py)
+copy_e2e_python_files_from_parent_folder(ha_experimental ".." mg_utils.py)

tests/e2e/high_availability_experimental/client_initiated_failover.py

@@ -0,0 +1,224 @@
+# Copyright 2022 Memgraph Ltd.
+#
+# Use of this software is governed by the Business Source License
+# included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+# License, and you may not use this file except in compliance with the Business Source License.
+#
+# As of the Change Date specified in that file, in accordance with
+# the Business Source License, use of this software will be governed
+# by the Apache License, Version 2.0, included in the file
+# licenses/APL.txt.
+
+import os
+import sys
+
+import interactive_mg_runner
+import pytest
+from common import execute_and_fetch_all
+from mg_utils import mg_sleep_and_assert
+
+interactive_mg_runner.SCRIPT_DIR = os.path.dirname(os.path.realpath(__file__))
+interactive_mg_runner.PROJECT_DIR = os.path.normpath(
+    os.path.join(interactive_mg_runner.SCRIPT_DIR, "..", "..", "..", "..")
+)
+interactive_mg_runner.BUILD_DIR = os.path.normpath(os.path.join(interactive_mg_runner.PROJECT_DIR, "build"))
+interactive_mg_runner.MEMGRAPH_BINARY = os.path.normpath(os.path.join(interactive_mg_runner.BUILD_DIR, "memgraph"))
+
+MEMGRAPH_INSTANCES_DESCRIPTION = {
+    "instance_1": {
+        "args": ["--bolt-port", "7688", "--log-level", "TRACE", "--coordinator-server-port", "10011"],
+        "log_file": "replica1.log",
+        "setup_queries": ["SET REPLICATION ROLE TO REPLICA WITH PORT 10001;"],
+    },
+    "instance_2": {
+        "args": ["--bolt-port", "7689", "--log-level", "TRACE", "--coordinator-server-port", "10012"],
+        "log_file": "replica2.log",
+        "setup_queries": ["SET REPLICATION ROLE TO REPLICA WITH PORT 10002;"],
+    },
+    "instance_3": {
+        "args": ["--bolt-port", "7687", "--log-level", "TRACE", "--coordinator-server-port", "10013"],
+        "log_file": "main.log",
+        "setup_queries": [
+            "REGISTER REPLICA instance_1 SYNC TO '127.0.0.1:10001'",
+            "REGISTER REPLICA instance_2 SYNC TO '127.0.0.1:10002'",
+        ],
+    },
+    "coordinator": {
+        "args": ["--bolt-port", "7690", "--log-level=TRACE", "--coordinator"],
+        "log_file": "replica3.log",
+        "setup_queries": [
+            "REGISTER REPLICA instance_1 SYNC TO '127.0.0.1:10001' WITH COORDINATOR SERVER ON '127.0.0.1:10011';",
+            "REGISTER REPLICA instance_2 SYNC TO '127.0.0.1:10002' WITH COORDINATOR SERVER ON '127.0.0.1:10012';",
+            "REGISTER MAIN instance_3 WITH COORDINATOR SERVER ON '127.0.0.1:10013';",
+        ],
+    },
+}
+
+
+def test_show_replication_cluster(connection):
+    # Goal of this test is to check the SHOW REPLICATION CLUSTER command.
+    # 1. We start all replicas, main and coordinator manually: we want to be able to kill them ourselves without relying on external tooling to kill processes.
+    # 2. We check that all replicas and main have the correct state: they should all be alive.
+    # 3. We kill one replica. It should not appear anymore in the SHOW REPLICATION CLUSTER command.
+    # 4. We kill main. It should not appear anymore in the SHOW REPLICATION CLUSTER command.
+
+    # 1.
+    interactive_mg_runner.start_all(MEMGRAPH_INSTANCES_DESCRIPTION)
+
+    cursor = connection(7690, "coordinator").cursor()
+
+    # 2.
+
+    # We leave some time for the coordinator to realise the replicas are down.
+    def retrieve_data():
+        return set(execute_and_fetch_all(cursor, "SHOW REPLICATION CLUSTER;"))
+
+    expected_data = {
+        ("instance_1", "127.0.0.1:10011", True, "replica"),
+        ("instance_2", "127.0.0.1:10012", True, "replica"),
+        ("instance_3", "127.0.0.1:10013", True, "main"),
+    }
+    mg_sleep_and_assert(expected_data, retrieve_data)
+
+    # 3.
+    interactive_mg_runner.kill(MEMGRAPH_INSTANCES_DESCRIPTION, "instance_1")
+
+    expected_data = {
+        ("instance_2", "127.0.0.1:10012", True, "replica"),
+        ("instance_3", "127.0.0.1:10013", True, "main"),
+        ("instance_1", "127.0.0.1:10011", False, "replica"),
+    }
+    mg_sleep_and_assert(expected_data, retrieve_data)
+
+    # 4.
+    interactive_mg_runner.kill(MEMGRAPH_INSTANCES_DESCRIPTION, "instance_3")
+
+    expected_data = {
+        ("instance_2", "127.0.0.1:10012", True, "replica"),
+        ("instance_1", "127.0.0.1:10011", False, "replica"),
+        ("instance_3", "127.0.0.1:10013", False, "main"),
+    }
+    mg_sleep_and_assert(expected_data, retrieve_data)
+
+
+def test_simple_client_initiated_failover(connection):
+    # 1. Start all instances
+    # 2. Kill main
+    # 3. Run DO FAILOVER on COORDINATOR
+    # 4. Assert new config on coordinator by running show replication cluster
+    # 5. Assert replicas on new main
+
+    # 1.
+    interactive_mg_runner.start_all(MEMGRAPH_INSTANCES_DESCRIPTION)
+
+    # 2.
+    main_cursor = connection(7687, "instance_3").cursor()
+    expected_data_on_main = {
+        ("instance_1", "127.0.0.1:10001", "sync", 0, 0, "ready"),
+        ("instance_2", "127.0.0.1:10002", "sync", 0, 0, "ready"),
+    }
+    actual_data_on_main = set(execute_and_fetch_all(main_cursor, "SHOW REPLICAS;"))
+    assert actual_data_on_main == expected_data_on_main
+
+    interactive_mg_runner.kill(MEMGRAPH_INSTANCES_DESCRIPTION, "instance_3")
+    coord_cursor = connection(7690, "coordinator").cursor()
+
+    def retrieve_data_show_repl_cluster():
+        return set(execute_and_fetch_all(coord_cursor, "SHOW REPLICATION CLUSTER;"))
+
+    expected_data_on_coord = {
+        ("instance_1", "127.0.0.1:10011", True, "replica"),
+        ("instance_2", "127.0.0.1:10012", True, "replica"),
+        ("instance_3", "127.0.0.1:10013", False, "main"),
+    }
+    mg_sleep_and_assert(expected_data_on_coord, retrieve_data_show_repl_cluster)
+
+    # 3.
+    execute_and_fetch_all(coord_cursor, "DO FAILOVER")
+
+    expected_data_on_coord = {
+        ("instance_1", "127.0.0.1:10011", True, "main"),
+        ("instance_2", "127.0.0.1:10012", True, "replica"),
+    }
+    mg_sleep_and_assert(expected_data_on_coord, retrieve_data_show_repl_cluster)
+
+    # 4.
+    new_main_cursor = connection(7688, "instance_1").cursor()
+
+    def retrieve_data_show_replicas():
+        return set(execute_and_fetch_all(new_main_cursor, "SHOW REPLICAS;"))
+
+    expected_data_on_new_main = {
+        ("instance_2", "127.0.0.1:10002", "sync", 0, 0, "ready"),
+    }
+    mg_sleep_and_assert(expected_data_on_new_main, retrieve_data_show_replicas)
+
+
+def test_failover_fails_all_replicas_down(connection):
+    # 1. Start all instances
+    # 2. Kill all replicas
+    # 3. Kill main
+    # 4. Run DO FAILOVER on COORDINATOR. Assert exception is being thrown due to all replicas being down
+    # 5. Assert cluster status didn't change
+
+    # 1.
+    interactive_mg_runner.start_all(MEMGRAPH_INSTANCES_DESCRIPTION)
+
+    # 2.
+    interactive_mg_runner.kill(MEMGRAPH_INSTANCES_DESCRIPTION, "instance_1")
+    interactive_mg_runner.kill(MEMGRAPH_INSTANCES_DESCRIPTION, "instance_2")
+
+    # 3.
+    interactive_mg_runner.kill(MEMGRAPH_INSTANCES_DESCRIPTION, "instance_3")
+
+    coord_cursor = connection(7690, "coordinator").cursor()
+    # 4.
+    with pytest.raises(Exception) as e:
+        execute_and_fetch_all(coord_cursor, "DO FAILOVER;")
+    assert str(e.value) == "Failover aborted since all replicas are down!"
+
+    # 5.
+
+    def retrieve_data():
+        return set(execute_and_fetch_all(coord_cursor, "SHOW REPLICATION CLUSTER;"))
+
+    expected_data_on_coord = {
+        ("instance_1", "127.0.0.1:10011", False, "replica"),
+        ("instance_2", "127.0.0.1:10012", False, "replica"),
+        ("instance_3", "127.0.0.1:10013", False, "main"),
+    }
+    mg_sleep_and_assert(expected_data_on_coord, retrieve_data)
+
+
+def test_failover_fails_main_is_alive(connection):
+    # 1. Start all instances
+    # 2. Run DO FAILOVER on COORDINATOR. Assert exception is being thrown due to main is still live.
+    # 3. Assert cluster status didn't change
+
+    # 1.
+    interactive_mg_runner.start_all(MEMGRAPH_INSTANCES_DESCRIPTION)
+
+    # 2.
+    coord_cursor = connection(7690, "coordinator").cursor()
+
+    def retrieve_data():
+        return set(execute_and_fetch_all(coord_cursor, "SHOW REPLICATION CLUSTER;"))
+
+    expected_data_on_coord = {
+        ("instance_1", "127.0.0.1:10011", True, "replica"),
+        ("instance_2", "127.0.0.1:10012", True, "replica"),
+        ("instance_3", "127.0.0.1:10013", True, "main"),
+    }
+    mg_sleep_and_assert(expected_data_on_coord, retrieve_data)
+
+    # 4.
+    with pytest.raises(Exception) as e:
+        execute_and_fetch_all(coord_cursor, "DO FAILOVER;")
+    assert str(e.value) == "Failover aborted since main is alive!"
+
+    # 5.
+    mg_sleep_and_assert(expected_data_on_coord, retrieve_data)
+
+
+if __name__ == "__main__":
+    sys.exit(pytest.main([__file__, "-rA"]))

tests/e2e/high_availability_experimental/common.py

@@ -0,0 +1,25 @@
+# Copyright 2022 Memgraph Ltd.
+#
+# Use of this software is governed by the Business Source License
+# included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+# License, and you may not use this file except in compliance with the Business Source License.
+#
+# As of the Change Date specified in that file, in accordance with
+# the Business Source License, use of this software will be governed
+# by the Apache License, Version 2.0, included in the file
+# licenses/APL.txt.
+
+import typing
+
+import mgclient
+
+
+def execute_and_fetch_all(cursor: mgclient.Cursor, query: str, params: dict = {}) -> typing.List[tuple]:
+    cursor.execute(query, params)
+    return cursor.fetchall()
+
+
+def connect(**kwargs) -> mgclient.Connection:
+    connection = mgclient.connect(**kwargs)
+    connection.autocommit = True
+    return connection

tests/e2e/high_availability_experimental/conftest.py

@@ -0,0 +1,43 @@
+# Copyright 2022 Memgraph Ltd.
+#
+# Use of this software is governed by the Business Source License
+# included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+# License, and you may not use this file except in compliance with the Business Source License.
+#
+# As of the Change Date specified in that file, in accordance with
+# the Business Source License, use of this software will be governed
+# by the Apache License, Version 2.0, included in the file
+# licenses/APL.txt.
+
+import pytest
+from common import connect, execute_and_fetch_all
+
+
+# The fixture here is more complex because the connection has to be
+# parameterized based on the test parameters (info has to be available on both
+# sides).
+#
+# https://docs.pytest.org/en/latest/example/parametrize.html#indirect-parametrization
+# is not an elegant/feasible solution here.
+#
+# The solution was independently developed and then I stumbled upon the same
+# approach here https://stackoverflow.com/a/68286553/4888809 which I think is
+# optimal.
+@pytest.fixture(scope="function")
+def connection():
+    connection_holder = None
+    role_holder = None
+
+    def inner_connection(port, role):
+        nonlocal connection_holder, role_holder
+        connection_holder = connect(host="localhost", port=port)
+        role_holder = role
+        return connection_holder
+
+    yield inner_connection
+
+    # Only main instance can be cleaned up because replicas do NOT accept
+    # writes.
+    if role_holder == "main":
+        cursor = connection_holder.cursor()
+        execute_and_fetch_all(cursor, "MATCH (n) DETACH DELETE n;")

tests/e2e/high_availability_experimental/coordinator.py

@@ -0,0 +1,98 @@
+# Copyright 2022 Memgraph Ltd.
+#
+# Use of this software is governed by the Business Source License
+# included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+# License, and you may not use this file except in compliance with the Business Source License.
+#
+# As of the Change Date specified in that file, in accordance with
+# the Business Source License, use of this software will be governed
+# by the Apache License, Version 2.0, included in the file
+# licenses/APL.txt.
+
+import sys
+
+import pytest
+from common import execute_and_fetch_all
+from mg_utils import mg_sleep_and_assert
+
+
+def test_disable_cypher_queries(connection):
+    cursor = connection(7690, "coordinator").cursor()
+    with pytest.raises(Exception) as e:
+        execute_and_fetch_all(cursor, "CREATE (n:TestNode {prop: 'test'})")
+    assert str(e.value) == "Coordinator can run only coordinator queries!"
+
+
+def test_coordinator_cannot_be_replica_role(connection):
+    cursor = connection(7690, "coordinator").cursor()
+    with pytest.raises(Exception) as e:
+        execute_and_fetch_all(cursor, "SET REPLICATION ROLE TO REPLICA WITH PORT 10001;")
+    assert str(e.value) == "Coordinator can run only coordinator queries!"
+
+
+def test_coordinator_cannot_run_show_repl_role(connection):
+    cursor = connection(7690, "coordinator").cursor()
+    with pytest.raises(Exception) as e:
+        execute_and_fetch_all(cursor, "SHOW REPLICATION ROLE;")
+    assert str(e.value) == "Coordinator can run only coordinator queries!"
+
+
+def test_coordinator_show_replication_cluster(connection):
+    cursor = connection(7690, "coordinator").cursor()
+
+    def retrieve_data():
+        return set(execute_and_fetch_all(cursor, "SHOW REPLICATION CLUSTER;"))
+
+    expected_data = {
+        ("main", "127.0.0.1:10013", True, "main"),
+        ("replica_1", "127.0.0.1:10011", True, "replica"),
+        ("replica_2", "127.0.0.1:10012", True, "replica"),
+    }
+    mg_sleep_and_assert(expected_data, retrieve_data)
+
+
+def test_coordinator_cannot_call_show_replicas(connection):
+    cursor = connection(7690, "coordinator").cursor()
+    with pytest.raises(Exception) as e:
+        execute_and_fetch_all(cursor, "SHOW REPLICAS;")
+    assert str(e.value) == "Coordinator can run only coordinator queries!"
+
+
+@pytest.mark.parametrize(
+    "port, role",
+    [(7687, "main"), (7688, "replica"), (7689, "replica")],
+)
+def test_main_and_replicas_cannot_call_show_repl_cluster(port, role, connection):
+    cursor = connection(port, role).cursor()
+    with pytest.raises(Exception) as e:
+        execute_and_fetch_all(cursor, "SHOW REPLICATION CLUSTER;")
+    assert str(e.value) == "Only coordinator can run SHOW REPLICATION CLUSTER."
+
+
+@pytest.mark.parametrize(
+    "port, role",
+    [(7687, "main"), (7688, "replica"), (7689, "replica")],
+)
+def test_main_and_replicas_cannot_register_coord_server(port, role, connection):
+    cursor = connection(port, role).cursor()
+    with pytest.raises(Exception) as e:
+        execute_and_fetch_all(
+            cursor,
+            "REGISTER REPLICA instance_1 SYNC TO '127.0.0.1:10001' WITH COORDINATOR SERVER ON '127.0.0.1:10011';",
+        )
+    assert str(e.value) == "Only coordinator can register coordinator server!"
+
+
+@pytest.mark.parametrize(
+    "port, role",
+    [(7687, "main"), (7688, "replica"), (7689, "replica")],
+)
+def test_main_and_replicas_cannot_run_do_failover(port, role, connection):
+    cursor = connection(port, role).cursor()
+    with pytest.raises(Exception) as e:
+        execute_and_fetch_all(cursor, "DO FAILOVER;")
+    assert str(e.value) == "Only coordinator can run DO FAILOVER!"
+
+
+if __name__ == "__main__":
+    sys.exit(pytest.main([__file__, "-rA"]))

tests/e2e/high_availability_experimental/uninitialized_cluster.py

@@ -0,0 +1,26 @@
+# Copyright 2022 Memgraph Ltd.
+#
+# Use of this software is governed by the Business Source License
+# included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+# License, and you may not use this file except in compliance with the Business Source License.
+#
+# As of the Change Date specified in that file, in accordance with
+# the Business Source License, use of this software will be governed
+# by the Apache License, Version 2.0, included in the file
+# licenses/APL.txt.
+
+import sys
+
+import pytest
+from common import execute_and_fetch_all
+
+
+def test_failover_on_non_setup_cluster(connection):
+    cursor = connection(7690, "coordinator").cursor()
+    with pytest.raises(Exception) as e:
+        execute_and_fetch_all(cursor, "DO FAILOVER;")
+    assert str(e.value) == "Failover aborted since cluster is uninitialized!"
+
+
+if __name__ == "__main__":
+    sys.exit(pytest.main([__file__, "-rA"]))

tests/e2e/high_availability_experimental/workloads.yaml

@@ -0,0 +1,63 @@
+ha_cluster: &ha_cluster
+  cluster:
+    replica_1:
+      args: ["--bolt-port", "7688", "--log-level=TRACE", "--coordinator-server-port=10011"]
+      log_file: "replication-e2e-replica1.log"
+      setup_queries: ["SET REPLICATION ROLE TO REPLICA WITH PORT 10001;"]
+    replica_2:
+      args: ["--bolt-port", "7689", "--log-level=TRACE", "--coordinator-server-port=10012"]
+      log_file: "replication-e2e-replica2.log"
+      setup_queries: ["SET REPLICATION ROLE TO REPLICA WITH PORT 10002;"]
+    main:
+      args: ["--bolt-port", "7687", "--log-level=TRACE", "--coordinator-server-port=10013"]
+      log_file: "replication-e2e-main.log"
+      setup_queries: [
+        "REGISTER REPLICA replica_1 SYNC TO '127.0.0.1:10001'",
+        "REGISTER REPLICA replica_2 SYNC TO '127.0.0.1:10002'",
+      ]
+    coordinator:
+      args: ["--bolt-port", "7690", "--log-level=TRACE", "--coordinator"]
+      log_file: "replication-e2e-coordinator.log"
+      setup_queries: [
+        "REGISTER MAIN main WITH COORDINATOR SERVER ON '127.0.0.1:10013'",
+        "REGISTER REPLICA replica_1 SYNC TO '127.0.0.1:10001' WITH COORDINATOR SERVER ON '127.0.0.1:10011'",
+        "REGISTER REPLICA replica_2 SYNC TO '127.0.0.1:10002' WITH COORDINATOR SERVER ON '127.0.0.1:10012'",
+      ]
+
+noninitialized_cluster: &noninitialized_cluster
+  cluster:
+    replica_1:
+      args: ["--bolt-port", "7688", "--log-level=TRACE", "--coordinator-server-port=10011"]
+      log_file: "replication-e2e-replica1.log"
+      setup_queries: ["SET REPLICATION ROLE TO REPLICA WITH PORT 10001;"]
+    replica_2:
+      args: ["--bolt-port", "7689", "--log-level=TRACE", "--coordinator-server-port=10012"]
+      log_file: "replication-e2e-replica2.log"
+      setup_queries: ["SET REPLICATION ROLE TO REPLICA WITH PORT 10002;"]
+    main:
+      args: ["--bolt-port", "7687", "--log-level=TRACE", "--coordinator-server-port=10013"]
+      log_file: "replication-e2e-main.log"
+      setup_queries: [
+        "REGISTER REPLICA replica_1 SYNC TO '127.0.0.1:10001'",
+        "REGISTER REPLICA replica_2 SYNC TO '127.0.0.1:10002'",
+      ]
+    coordinator:
+      args: ["--bolt-port", "7690", "--log-level=TRACE", "--coordinator"]
+      log_file: "replication-e2e-coordinator.log"
+      setup_queries: []
+
+
+workloads:
+  - name: "Coordinator"
+    binary: "tests/e2e/pytest_runner.sh"
+    args: ["high_availability_experimental/coordinator.py"]
+    <<: *ha_cluster
+
+  - name: "Uninitialized cluster"
+    binary: "tests/e2e/pytest_runner.sh"
+    args: ["high_availability_experimental/uninitialized_cluster.py"]
+    <<: *noninitialized_cluster
+
+  - name: "Client initiated failover"
+    binary: "tests/e2e/pytest_runner.sh"
+    args: ["high_availability_experimental/client_initiated_failover.py"]

tests/e2e/lba_procedures/show_privileges.py

@@ -40,6 +40,7 @@ BASIC_PRIVILEGES = [
     "STORAGE_MODE",
     "MULTI_DATABASE_EDIT",
     "MULTI_DATABASE_USE",
+    "COORDINATOR",
 ]
 
 
@@ -63,7 +64,7 @@ def test_lba_procedures_show_privileges_first_user():
     cursor = connect(username="Josip", password="").cursor()
     result = execute_and_fetch_all(cursor, "SHOW PRIVILEGES FOR Josip;")
 
-    assert len(result) == 34
+    assert len(result) == 35
 
     fine_privilege_results = [res for res in result if res[0] not in BASIC_PRIVILEGES]
 

tests/e2e/replication/CMakeLists.txt

@@ -9,13 +9,13 @@ target_link_libraries(memgraph__e2e__replication__indices gflags mgclient mg-uti
 add_executable(memgraph__e2e__replication__read_write_benchmark read_write_benchmark.cpp)
 target_link_libraries(memgraph__e2e__replication__read_write_benchmark gflags json mgclient mg-utils mg-io Threads::Threads)
 
-copy_e2e_python_files(replication_show common.py)
+copy_e2e_python_files(replication common.py)
-copy_e2e_python_files(replication_show conftest.py)
+copy_e2e_python_files(replication conftest.py)
-copy_e2e_python_files(replication_show show.py)
+copy_e2e_python_files(replication show.py)
-copy_e2e_python_files(replication_show show_while_creating_invalid_state.py)
+copy_e2e_python_files(replication show_while_creating_invalid_state.py)
-copy_e2e_python_files(replication_show edge_delete.py)
+copy_e2e_python_files(replication edge_delete.py)
-copy_e2e_python_files_from_parent_folder(replication_show ".." memgraph.py)
+copy_e2e_python_files_from_parent_folder(replication ".." memgraph.py)
-copy_e2e_python_files_from_parent_folder(replication_show ".." interactive_mg_runner.py)
+copy_e2e_python_files_from_parent_folder(replication ".." interactive_mg_runner.py)
-copy_e2e_python_files_from_parent_folder(replication_show ".." mg_utils.py)
+copy_e2e_python_files_from_parent_folder(replication ".." mg_utils.py)
 
 copy_e2e_files(replication workloads.yaml)

tests/e2e/replication/workloads.yaml

@@ -11,7 +11,7 @@ template_validation_queries: &template_validation_queries
 template_simple_cluster: &template_simple_cluster
   cluster:
     replica_1:
-      args: [ "--bolt-port", "7688", "--log-level=TRACE" ]
+      args: [ "--bolt-port", "7688", "--log-level=TRACE"]
       log_file: "replication-e2e-replica1.log"
       setup_queries: [ "SET REPLICATION ROLE TO REPLICA WITH PORT 10001;" ]
     replica_2:
@@ -25,6 +25,7 @@ template_simple_cluster: &template_simple_cluster
         "REGISTER REPLICA replica_1 SYNC TO '127.0.0.1:10001'",
         "REGISTER REPLICA replica_2 ASYNC TO '127.0.0.1:10002'",
       ]
+
 template_cluster: &template_cluster
   cluster:
     replica_1:
@@ -50,7 +51,6 @@ template_cluster: &template_cluster
         "REGISTER REPLICA replica_2 SYNC TO '127.0.0.1:10002'",
         "REGISTER REPLICA replica_3 ASYNC TO '127.0.0.1:10003'"
       ]
-      <<: *template_validation_queries
 
 workloads:
   - name: "Constraints"

tests/unit/CMakeLists.txt

@@ -350,7 +350,7 @@ add_unit_test(storage_v2_wal_file.cpp)
 target_link_libraries(${test_prefix}storage_v2_wal_file mg-storage-v2 storage_test_utils fmt)
 
 add_unit_test(storage_v2_replication.cpp)
-target_link_libraries(${test_prefix}storage_v2_replication mg-storage-v2 mg-dbms fmt)
+target_link_libraries(${test_prefix}storage_v2_replication mg-storage-v2 mg-dbms fmt mg-repl_coord_glue)
 
 add_unit_test(storage_v2_isolation_level.cpp)
 target_link_libraries(${test_prefix}storage_v2_isolation_level mg-storage-v2)
@@ -368,7 +368,7 @@ add_unit_test(storage_v2_storage_mode.cpp)
 target_link_libraries(${test_prefix}storage_v2_storage_mode mg-storage-v2 storage_test_utils mg-query mg-glue)
 
 add_unit_test(replication_persistence_helper.cpp)
-target_link_libraries(${test_prefix}replication_persistence_helper mg-storage-v2)
+target_link_libraries(${test_prefix}replication_persistence_helper mg-storage-v2 mg-repl_coord_glue)
 
 add_unit_test(auth_checker.cpp)
 target_link_libraries(${test_prefix}auth_checker mg-glue mg-auth)
@@ -389,7 +389,7 @@ endif()
 # Test mg-slk
 if(MG_ENTERPRISE)
   add_unit_test(slk_advanced.cpp)
-  target_link_libraries(${test_prefix}slk_advanced mg-storage-v2)
+  target_link_libraries(${test_prefix}slk_advanced mg-storage-v2 mg-replication mg-coordination mg-repl_coord_glue)
 endif()
 
 add_unit_test(slk_core.cpp)

tests/unit/cypher_main_visitor.cpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -43,6 +43,7 @@
 #include "query/procedure/module.hpp"
 #include "query/typed_value.hpp"
 
+#include "utils/logging.hpp"
 #include "utils/string.hpp"
 #include "utils/variant_helpers.hpp"
 
@@ -2550,7 +2551,7 @@ TEST_P(CypherMainVisitorTest, ShowUsersForRole) {
 void check_replication_query(Base *ast_generator, const ReplicationQuery *query, const std::string name,
                              const std::optional<TypedValue> socket_address, const ReplicationQuery::SyncMode sync_mode,
                              const std::optional<TypedValue> port = {}) {
-  EXPECT_EQ(query->replica_name_, name);
+  EXPECT_EQ(query->instance_name_, name);
   EXPECT_EQ(query->sync_mode_, sync_mode);
   ASSERT_EQ(static_cast<bool>(query->socket_address_), static_cast<bool>(socket_address));
   if (socket_address) {
@@ -2597,7 +2598,7 @@ TEST_P(CypherMainVisitorTest, TestSetReplicationMode) {
   }
 
   {
-    const std::string query = "SET REPLICATION ROLE TO MAIN WITH PORT 10000";
+    const std::string query = "SET REPLICATION ROLE TO REPLICA";
     ASSERT_THROW(ast_generator.ParseQuery(query), SemanticException);
   }
 
@@ -2631,6 +2632,77 @@ TEST_P(CypherMainVisitorTest, TestRegisterReplicationQuery) {
                           ReplicationQuery::SyncMode::SYNC);
 }
 
+#ifdef MG_ENTERPRISE
+TEST_P(CypherMainVisitorTest, TestRegisterCoordinatorServer) {
+  auto &ast_generator = *GetParam();
+
+  {
+    const std::string faulty_query_1 = "REGISTER MAIN COORDINATOR SERVER TO";
+    ASSERT_THROW(ast_generator.ParseQuery(faulty_query_1), SyntaxException);
+  }
+
+  {
+    const std::string faulty_query_2 = "REGISTER MAIN COORDINATOR SERVER TO MAIN";
+    ASSERT_THROW(ast_generator.ParseQuery(faulty_query_2), SyntaxException);
+  }
+
+  {
+    std::string full_query = "REGISTER MAIN main WITH COORDINATOR SERVER ON '127.0.0.1:10011';";
+
+    auto *full_query_parsed = dynamic_cast<CoordinatorQuery *>(ast_generator.ParseQuery(full_query));
+
+    ASSERT_TRUE(full_query_parsed);
+    EXPECT_EQ(full_query_parsed->action_, CoordinatorQuery::Action::REGISTER_MAIN_COORDINATOR_SERVER);
+    EXPECT_EQ(full_query_parsed->role_, CoordinatorQuery::ReplicationRole::MAIN);
+    EXPECT_EQ(full_query_parsed->instance_name_, "main");
+    ast_generator.CheckLiteral(full_query_parsed->coordinator_socket_address_, "127.0.0.1:10011");
+    ASSERT_EQ(full_query_parsed->socket_address_, nullptr);
+  }
+
+  {
+    std::string full_query =
+        R"(REGISTER REPLICA replica_1 SYNC TO "127.0.0.1:10002" WITH COORDINATOR SERVER ON "127.0.0.1:10012")";
+    auto *full_query_parsed = dynamic_cast<CoordinatorQuery *>(ast_generator.ParseQuery(full_query));
+    ASSERT_TRUE(full_query_parsed);
+    EXPECT_EQ(full_query_parsed->action_, CoordinatorQuery::Action::REGISTER_REPLICA_COORDINATOR_SERVER);
+    EXPECT_EQ(full_query_parsed->role_, CoordinatorQuery::ReplicationRole::REPLICA);
+    ast_generator.CheckLiteral(full_query_parsed->socket_address_, "127.0.0.1:10002");
+    ast_generator.CheckLiteral(full_query_parsed->coordinator_socket_address_, "127.0.0.1:10012");
+    EXPECT_EQ(full_query_parsed->instance_name_, "replica_1");
+    EXPECT_EQ(full_query_parsed->sync_mode_, CoordinatorQuery::SyncMode::SYNC);
+  }
+
+  {
+    std::string full_query =
+        R"(REGISTER REPLICA replica_1 ASYNC TO '127.0.0.1:10002' WITH COORDINATOR SERVER ON '127.0.0.1:10012')";
+    auto *full_query_parsed = dynamic_cast<CoordinatorQuery *>(ast_generator.ParseQuery(full_query));
+    ASSERT_TRUE(full_query_parsed);
+    EXPECT_EQ(full_query_parsed->action_, CoordinatorQuery::Action::REGISTER_REPLICA_COORDINATOR_SERVER);
+    EXPECT_EQ(full_query_parsed->role_, CoordinatorQuery::ReplicationRole::REPLICA);
+    ast_generator.CheckLiteral(full_query_parsed->socket_address_, "127.0.0.1:10002");
+    ast_generator.CheckLiteral(full_query_parsed->coordinator_socket_address_, "127.0.0.1:10012");
+    EXPECT_EQ(full_query_parsed->instance_name_, "replica_1");
+    EXPECT_EQ(full_query_parsed->sync_mode_, CoordinatorQuery::SyncMode::ASYNC);
+  }
+}
+
+TEST_P(CypherMainVisitorTest, TestDoFailover) {
+  auto &ast_generator = *GetParam();
+
+  {
+    std::string invalid_query = "DO FAILO";
+    ASSERT_THROW(ast_generator.ParseQuery(invalid_query), SyntaxException);
+  }
+
+  {
+    std::string correct_query = "DO FAILOVER";
+    auto *correct_query_parsed = dynamic_cast<CoordinatorQuery *>(ast_generator.ParseQuery(correct_query));
+    ASSERT_TRUE(correct_query_parsed);
+    EXPECT_EQ(correct_query_parsed->action_, CoordinatorQuery::Action::DO_FAILOVER);
+  }
+}
+#endif
+
 TEST_P(CypherMainVisitorTest, TestDeleteReplica) {
   auto &ast_generator = *GetParam();
 
@@ -2640,7 +2712,7 @@ TEST_P(CypherMainVisitorTest, TestDeleteReplica) {
   std::string correct_query = "DROP REPLICA replica1";
   auto *correct_query_parsed = dynamic_cast<ReplicationQuery *>(ast_generator.ParseQuery(correct_query));
   ASSERT_TRUE(correct_query_parsed);
-  EXPECT_EQ(correct_query_parsed->replica_name_, "replica1");
+  EXPECT_EQ(correct_query_parsed->instance_name_, "replica1");
 }
 
 TEST_P(CypherMainVisitorTest, TestExplainRegularQuery) {
@@ -3645,7 +3717,7 @@ TEST_P(CypherMainVisitorTest, MemoryLimit) {
     ASSERT_TRUE(query->single_query_);
     auto *single_query = query->single_query_;
     ASSERT_EQ(single_query->clauses_.size(), 2U);
-    auto *call_proc = dynamic_cast<CallProcedure *>(single_query->clauses_[0]);
+    [[maybe_unused]] auto *call_proc = dynamic_cast<CallProcedure *>(single_query->clauses_[0]);
   }
 
   {
@@ -3705,7 +3777,7 @@ TEST_P(CypherMainVisitorTest, MemoryLimit) {
     ASSERT_TRUE(query->single_query_);
     auto *single_query = query->single_query_;
     ASSERT_EQ(single_query->clauses_.size(), 1U);
-    auto *call_proc = dynamic_cast<CallProcedure *>(single_query->clauses_[0]);
+    [[maybe_unused]] auto *call_proc = dynamic_cast<CallProcedure *>(single_query->clauses_[0]);
   }
 }
 

tests/unit/replication_persistence_helper.cpp

@@ -1,4 +1,4 @@
-// Copyright 2023 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -22,12 +22,7 @@
 
 using namespace memgraph::replication::durability;
 using namespace memgraph::replication;
-
+using namespace memgraph::replication_coordination_glue;
-static_assert(sizeof(ReplicationRoleEntry) == 168,
-              "Most likely you modified ReplicationRoleEntry without updating the tests. ");
-
-static_assert(sizeof(ReplicationReplicaEntry) == 160,
-              "Most likely you modified ReplicationReplicaEntry without updating the tests.");
 
 TEST(ReplicationDurability, V1Main) {
   auto const role_entry = ReplicationRoleEntry{.version = DurabilityVersion::V1,

tests/unit/slk_advanced.cpp

@@ -1,4 +1,4 @@
-// Copyright 2022 Memgraph Ltd.
+// Copyright 2024 Memgraph Ltd.
 //
 // Use of this software is governed by the Business Source License
 // included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
@@ -11,10 +11,13 @@
 
 #include <gtest/gtest.h>
 
+#include "coordination/coordinator_config.hpp"
+#include "coordination/coordinator_slk.hpp"
+#include "replication/config.hpp"
+#include "replication_coordination_glue/mode.hpp"
+#include "slk_common.hpp"
 #include "storage/v2/property_value.hpp"
 #include "storage/v2/replication/slk.hpp"
-
-#include "slk_common.hpp"
 #include "storage/v2/temporal.hpp"
 
 TEST(SlkAdvanced, PropertyValueList) {
@@ -114,3 +117,34 @@ TEST(SlkAdvanced, PropertyValueComplex) {
 
   ASSERT_EQ(original, decoded);
 }
+
+TEST(SlkAdvanced, ReplicationClientConfigs) {
+  using ReplicationClientInfo = memgraph::coordination::CoordinatorClientConfig::ReplicationClientInfo;
+  using ReplicationClientInfoVec = std::vector<ReplicationClientInfo>;
+  using ReplicationMode = memgraph::replication_coordination_glue::ReplicationMode;
+
+  ReplicationClientInfoVec original{ReplicationClientInfo{.instance_name = "replica1",
+                                                          .replication_mode = ReplicationMode::SYNC,
+                                                          .replication_ip_address = "127.0.0.1",
+                                                          .replication_port = 10000},
+                                    ReplicationClientInfo{.instance_name = "replica2",
+                                                          .replication_mode = ReplicationMode::ASYNC,
+                                                          .replication_ip_address = "127.0.1.1",
+                                                          .replication_port = 10010},
+                                    ReplicationClientInfo{
+                                        .instance_name = "replica3",
+                                        .replication_mode = ReplicationMode::ASYNC,
+                                        .replication_ip_address = "127.1.1.1",
+                                        .replication_port = 1110,
+                                    }};
+
+  memgraph::slk::Loopback loopback;
+  auto builder = loopback.GetBuilder();
+  memgraph::slk::Save(original, builder);
+
+  ReplicationClientInfoVec decoded;
+  auto reader = loopback.GetReader();
+  memgraph::slk::Load(&decoded, reader);
+
+  ASSERT_EQ(original, decoded);
+}

tests/unit/storage_v2_replication.cpp

@@ -39,9 +39,9 @@ using memgraph::dbms::RegisterReplicaError;
 using memgraph::dbms::ReplicationHandler;
 using memgraph::dbms::UnregisterReplicaResult;
 using memgraph::replication::ReplicationClientConfig;
-using memgraph::replication::ReplicationMode;
 using memgraph::replication::ReplicationRole;
 using memgraph::replication::ReplicationServerConfig;
+using memgraph::replication_coordination_glue::ReplicationMode;
 using memgraph::storage::Config;
 using memgraph::storage::EdgeAccessor;
 using memgraph::storage::Gid;