From efbae39f41df9e91f8b2fd16a5acb40bcc3d3ed4 Mon Sep 17 00:00:00 2001
From: Kruno Tomola Fabro <krunotf@memgraph.io>
Date: Sun, 11 Sep 2016 22:22:52 +0100
Subject: [PATCH] Added logic for cleaning older snapshots.

---
 config/memgraph.yaml                 |  1 +
 include/config/config.hpp            |  1 +
 include/snapshot/snapshot_engine.hpp |  8 ++++
 src/snapshot/snapshot_engine.cpp     | 58 +++++++++++++++++++++++++++-
 4 files changed, 66 insertions(+), 2 deletions(-)

diff --git a/config/memgraph.yaml b/config/memgraph.yaml
index 7049cf781..a272f3ae5 100644
--- a/config/memgraph.yaml
+++ b/config/memgraph.yaml
@@ -5,3 +5,4 @@ template_cpu_hpp_path: "./template/template_code_cpu.hpp"
 snapshots_path: "./snapshots"
 cleaning_cycle_sec: "60"
 snapshot_cycle_sec: "60"
+max_retained_snapshots: "3"
diff --git a/include/config/config.hpp b/include/config/config.hpp
index 30b2b3407..0fb9e42cb 100644
--- a/include/config/config.hpp
+++ b/include/config/config.hpp
@@ -25,6 +25,7 @@ constexpr const char *BARRIER_TEMPLATE_CPU_CPP_PATH =
 constexpr const char *SNAPSHOTS_PATH = "snapshots_path";
 constexpr const char *CLEANING_CYCLE_SEC = "cleaning_cycle_sec";
 constexpr const char *SNAPSHOT_CYCLE_SEC = "snapshot_cycle_sec";
+constexpr const char *MAX_RETAINED_SNAPSHOTS = "max_retained_snapshots";
 // -- all possible Memgraph's keys --
 
 inline size_t to_int(std::string &&s) { return stoull(s); }
diff --git a/include/snapshot/snapshot_engine.hpp b/include/snapshot/snapshot_engine.hpp
index 448771122..5cffc520f 100644
--- a/include/snapshot/snapshot_engine.hpp
+++ b/include/snapshot/snapshot_engine.hpp
@@ -32,6 +32,9 @@ public:
     bool make_snapshot();
 
 private:
+    // Removes excess of snapshots starting with oldest one.
+    void clean_snapshots();
+
     // Makes snapshot of given type
     bool make_snapshot(std::time_t now, const char *type);
 
@@ -55,5 +58,10 @@ private:
     Db &db;
     std::mutex guard;
     const std::string snapshot_folder;
+
+    // Determines how many newest snapshot will be preserved, while the other
+    // ones will be deleted.
+    const size_t max_retained_snapshots;
+
     std::atomic<size_t> snapshoted_no_v = {0};
 };
diff --git a/src/snapshot/snapshot_engine.cpp b/src/snapshot/snapshot_engine.cpp
index 45b605c90..e3fd9e5be 100644
--- a/src/snapshot/snapshot_engine.cpp
+++ b/src/snapshot/snapshot_engine.cpp
@@ -11,6 +11,7 @@
 
 SnapshotEngine::SnapshotEngine(Db &db, std::string const &name)
     : snapshot_folder(CONFIG(config::SNAPSHOTS_PATH)), db(db),
+      max_retained_snapshots(CONFIG_INTEGER(config::MAX_RETAINED_SNAPSHOTS)),
       logger(logging::log->logger("SnapshotEngine db[" + name + "]"))
 {
 }
@@ -19,7 +20,58 @@ bool SnapshotEngine::make_snapshot()
 {
     std::lock_guard<std::mutex> lock(guard);
     std::time_t now = std::time(nullptr);
-    return make_snapshot(now, "full");
+    if (make_snapshot(now, "full")) {
+        clean_snapshots();
+        return true;
+    } else {
+        return false;
+    }
+}
+
+void SnapshotEngine::clean_snapshots()
+{
+    logger.info("Started cleaning commit_file");
+    std::vector<std::string> lines;
+    {
+        std::ifstream commit_file(snapshot_commit_file());
+
+        std::string line;
+        while (std::getline(commit_file, line)) {
+            lines.push_back(line);
+        }
+    }
+
+    int n = lines.size() - max_retained_snapshots;
+    if (n > 0) {
+        std::ofstream commit_file(snapshot_commit_file(), std::fstream::trunc);
+
+        for (auto i = n; i < lines.size(); i++) {
+            commit_file << lines[i] << std::endl;
+        }
+
+        auto res = sys::flush_file_to_disk(commit_file);
+        if (res == 0) {
+            commit_file.close();
+            logger.info("Removed {} snapshot from commit_file", n);
+
+            for (auto i = 0; i < n; i++) {
+                auto res = std::remove(lines[i].c_str());
+                if (res == 0) {
+                    logger.info("Succesfully deleted snapshot file \"{}\"",
+                                lines[i]);
+                } else {
+                    logger.error(
+                        "Error {} occured while deleting snapshot file \"{}\"",
+                        res, lines[i]);
+                }
+            }
+
+        } else {
+            logger.error("Error {} occured while flushing commit file", res);
+        }
+    }
+
+    logger.info("Finished cleaning commit_file");
 }
 
 bool SnapshotEngine::make_snapshot(std::time_t now, const char *type)
@@ -38,7 +90,9 @@ bool SnapshotEngine::make_snapshot(std::time_t now, const char *type)
 
         SnapshotEncoder snap(snapshot_file);
 
-        auto old_trans = tx::TransactionRead(db.tx_engine);
+        auto old_trans =
+            tx::TransactionRead(db.tx_engine); // Overenginered for incremental
+                                               // snapshot. Can be removed.
         snapshot(t, snap, old_trans);
 
         auto res = sys::flush_file_to_disk(snapshot_file);