add the emitter count method to the bus

Merge pull request #28 from libp2p/dependabot/go_modules/github.com/libp2p/go-libp2p-core-0.5.0
Bump github.com/libp2p/go-libp2p-core from 0.3.0 to 0.5.0
2026-08-20 15:03:27 +08:00 · 2020-03-26 10:53:55 +05:30 · 2020-03-11 11:48:10 -07:00 · 2020-03-09 11:18:09 +00:00 · 2019-12-17 12:46:43 +01:00 · 2019-12-12 11:19:39 +00:00
9 changed files with 814 additions and 252 deletions
--- a/.travis.yml
+++ b/.travis.yml
@@ -0,0 +1,30 @@
+os:
+  - linux
+
+language: go
+
+go:
+  - 1.13.x
+
+env:
+  global:
+    - GOTFLAGS="-race"
+  matrix:
+    - BUILD_DEPTYPE=gomod
+
+
+# disable travis install
+install:
+  - true
+
+script:
+  - bash <(curl -s https://raw.githubusercontent.com/ipfs/ci-helpers/master/travis-ci/run-standard-tests.sh)
+
+
+cache:
+  directories:
+    - $GOPATH/pkg/mod
+    - $HOME/.cache/go-build
+
+notifications:
+  email: false
--- a/README.md
+++ b/README.md
@@ -5,10 +5,10 @@
 [![](https://img.shields.io/badge/freenode-%23libp2p-yellow.svg?style=flat-square)](http://webchat.freenode.net/?channels=%23libp2p)
 [![GoDoc](https://godoc.org/github.com/libp2p/go-eventbus?status.svg)](https://godoc.org/github.com/libp2p/go-eventbus)
 [![Coverage Status](https://coveralls.io/repos/github/libp2p/go-eventbus/badge.svg?branch=master)](https://coveralls.io/github/libp2p/go-eventbus?branch=master)
-[![Build Status](https://travis-ci.org/libp2p/go-eventbus.svg?branch=master)](https://travis-ci.org/libp2p/go-eventbus)
+[![Build Status](https://travis-ci.com/libp2p/go-eventbus.svg?branch=master)](https://travis-ci.com/libp2p/go-eventbus)
 [![Discourse posts](https://img.shields.io/discourse/https/discuss.libp2p.io/posts.svg)](https://discuss.libp2p.io)

-> Simple and fast Go event bus
+> Simple and fast eventbus for type-based local event delivery.

 ## Install

--- a/basic.go
+++ b/basic.go
@@ -1,4 +1,4 @@
-package event
+package eventbus

 import (
 	"errors"
@@ -6,185 +6,278 @@ import (
 	"reflect"
 	"sync"
 	"sync/atomic"
+
+	"github.com/libp2p/go-libp2p-core/event"
 )

 ///////////////////////
 // BUS

-type bus struct {
-	lk sync.Mutex
-	nodes map[string]*node
+// basicBus is a type-based event delivery system
+type basicBus struct {
+	lk    sync.Mutex
+	nodes map[reflect.Type]*node
 }

-func NewBus() Bus {
-	return &bus{
-		nodes: map[string]*node{},
+var _ event.Bus = (*basicBus)(nil)
+
+type emitter struct {
+	n       *node
+	typ     reflect.Type
+	closed  int32
+	dropper func(reflect.Type)
+}
+
+func (e *emitter) Emit(evt interface{}) error {
+	if atomic.LoadInt32(&e.closed) != 0 {
+		return fmt.Errorf("emitter is closed")
+	}
+	e.n.emit(evt)
+	return nil
+}
+
+func (e *emitter) Close() error {
+	if !atomic.CompareAndSwapInt32(&e.closed, 0, 1) {
+		return fmt.Errorf("closed an emitter more than once")
+	}
+	if atomic.AddInt32(&e.n.nEmitters, -1) == 0 {
+		e.dropper(e.typ)
+	}
+	return nil
+}
+
+func NewBus() event.Bus {
+	return &basicBus{
+		nodes: map[reflect.Type]*node{},
 	}
 }

-func (b *bus) withNode(typ reflect.Type, cb func(*node)) error {
-	path := typePath(typ)
-
+func (b *basicBus) withNode(typ reflect.Type, cb func(*node), async func(*node)) {
 	b.lk.Lock()

-	n, ok := b.nodes[path]
+	n, ok := b.nodes[typ]
 	if !ok {
 		n = newNode(typ)
-		b.nodes[path] = n
+		b.nodes[typ] = n
 	}

 	n.lk.Lock()
 	b.lk.Unlock()
-	defer n.lk.Unlock()
+
 	cb(n)
-	return nil
+
+	if async == nil {
+		n.lk.Unlock()
+	} else {
+		go func() {
+			defer n.lk.Unlock()
+			async(n)
+		}()
+	}
 }

-func (b *bus) tryDropNode(typ reflect.Type) {
-	path := typePath(typ)
-
+func (b *basicBus) tryDropNode(typ reflect.Type) {
 	b.lk.Lock()
-	n, ok := b.nodes[path]
+	n, ok := b.nodes[typ]
 	if !ok { // already dropped
 		b.lk.Unlock()
 		return
 	}

 	n.lk.Lock()
-	if n.nEmitters > 0 || len(n.sinks) > 0 {
+	if atomic.LoadInt32(&n.nEmitters) > 0 || len(n.sinks) > 0 {
 		n.lk.Unlock()
 		b.lk.Unlock()
 		return // still in use
 	}
 	n.lk.Unlock()

-	delete(b.nodes, path)
+	delete(b.nodes, typ)
 	b.lk.Unlock()
 }

-func (b *bus) Subscribe(typedChan interface{}, opts ...SubOption) (c CancelFunc, err error) {
-	var settings SubSettings
+type sub struct {
+	ch      chan interface{}
+	nodes   []*node
+	dropper func(reflect.Type)
+}
+
+func (s *sub) Out() <-chan interface{} {
+	return s.ch
+}
+
+func (s *sub) Close() error {
+	go func() {
+		// drain the event channel, will return when closed and drained.
+		// this is necessary to unblock publishes to this channel.
+		for range s.ch {
+		}
+	}()
+
+	for _, n := range s.nodes {
+		n.lk.Lock()
+
+		for i := 0; i < len(n.sinks); i++ {
+			if n.sinks[i] == s.ch {
+				n.sinks[i], n.sinks[len(n.sinks)-1] = n.sinks[len(n.sinks)-1], nil
+				n.sinks = n.sinks[:len(n.sinks)-1]
+				break
+			}
+		}
+
+		tryDrop := len(n.sinks) == 0 && atomic.LoadInt32(&n.nEmitters) == 0
+
+		n.lk.Unlock()
+
+		if tryDrop {
+			s.dropper(n.typ)
+		}
+	}
+	close(s.ch)
+	return nil
+}
+
+var _ event.Subscription = (*sub)(nil)
+
+// Subscribe creates new subscription. Failing to drain the channel will cause
+// publishers to get blocked. CancelFunc is guaranteed to return after last send
+// to the channel
+func (b *basicBus) Subscribe(evtTypes interface{}, opts ...event.SubscriptionOpt) (_ event.Subscription, err error) {
+	settings := subSettings(subSettingsDefault)
 	for _, opt := range opts {
 		if err := opt(&settings); err != nil {
 			return nil, err
 		}
 	}

-	refCh := reflect.ValueOf(typedChan)
-	typ := refCh.Type()
-	if typ.Kind() != reflect.Chan {
-		return nil, errors.New("expected a channel")
-	}
-	if typ.ChanDir() & reflect.SendDir == 0 {
-		return nil, errors.New("channel doesn't allow send")
+	types, ok := evtTypes.([]interface{})
+	if !ok {
+		types = []interface{}{evtTypes}
 	}

-	if settings.forcedType != nil {
-		if settings.forcedType.Elem().AssignableTo(typ) {
-			return nil, fmt.Errorf("forced type %s cannot be sent to chan %s", settings.forcedType, typ)
+	out := &sub{
+		ch:    make(chan interface{}, settings.buffer),
+		nodes: make([]*node, len(types)),
+
+		dropper: b.tryDropNode,
+	}
+
+	for _, etyp := range types {
+		if reflect.TypeOf(etyp).Kind() != reflect.Ptr {
+			return nil, errors.New("subscribe called with non-pointer type")
 		}
-		typ = settings.forcedType
 	}

-	err = b.withNode(typ.Elem(), func(n *node) {
-		// when all subs are waiting on this channel, setting this to 1 doesn't
-		// really affect benchmarks
-		i := n.sub(refCh)
-		c = func() {
-			n.lk.Lock()
-			delete(n.sinks, i)
-			tryDrop := len(n.sinks) == 0 && n.nEmitters == 0
-			n.lk.Unlock()
-			if tryDrop {
-				b.tryDropNode(typ.Elem())
+	for i, etyp := range types {
+		typ := reflect.TypeOf(etyp)
+
+		b.withNode(typ.Elem(), func(n *node) {
+			n.sinks = append(n.sinks, out.ch)
+			out.nodes[i] = n
+		}, func(n *node) {
+			if n.keepLast {
+				l := n.last
+				if l == nil {
+					return
+				}
+				out.ch <- l
 			}
-		}
-	})
-	return
+		})
+	}
+
+	return out, nil
 }

-func (b *bus) Emitter(evtType interface{}, _ ...EmitterOption) (e EmitFunc, c CancelFunc, err error) {
+// Emitter creates new emitter
+//
+// eventType accepts typed nil pointers, and uses the type information to
+// select output type
+//
+// Example:
+// emit, err := eventbus.Emitter(new(EventT))
+// defer emit.Close() // MUST call this after being done with the emitter
+//
+// emit(EventT{})
+func (b *basicBus) Emitter(evtType interface{}, opts ...event.EmitterOpt) (e event.Emitter, err error) {
+	var settings emitterSettings
+
+	for _, opt := range opts {
+		if err := opt(&settings); err != nil {
+			return nil, err
+		}
+	}
+
 	typ := reflect.TypeOf(evtType)
 	if typ.Kind() != reflect.Ptr {
-		return nil, nil, errors.New("emitter called with non-pointer type")
+		return nil, errors.New("emitter called with non-pointer type")
 	}
 	typ = typ.Elem()

-	err = b.withNode(typ, func(n *node) {
+	b.withNode(typ, func(n *node) {
 		atomic.AddInt32(&n.nEmitters, 1)
-		closed := false
-
-		e = func(event interface{}) {
-			if closed {
-				panic("emitter is closed")
-			}
-			n.emit(event)
-		}
-
-		c = func() {
-			closed = true
-			if atomic.AddInt32(&n.nEmitters, -1) == 0 {
-				b.tryDropNode(typ)
-			}
-		}
-	})
+		n.keepLast = n.keepLast || settings.makeStateful
+		e = &emitter{n: n, typ: typ, dropper: b.tryDropNode}
+	}, nil)
 	return
 }

+func (b *basicBus) EmitterCount(evtType interface{}) (int, error) {
+	// discern the type of the interface and ensure it's a pointer
+	typ := reflect.TypeOf(evtType)
+	if typ.Kind() != reflect.Ptr {
+		return 0, errors.New("emitterCount called with non-pointer type")
+	}
+	typ = typ.Elem()
+
+	// get the count
+	b.lk.Lock()
+	n, ok := b.nodes[typ]
+	if !ok {
+		b.lk.Unlock()
+		return 0, nil
+	}
+	b.lk.Unlock()
+
+	return int(atomic.LoadInt32(&n.nEmitters)), nil
+}
+
 ///////////////////////
 // NODE

 type node struct {
-	// Note: make sure to NEVER lock bus.lk when this lock is held
-	lk sync.RWMutex
+	// Note: make sure to NEVER lock basicBus.lk when this lock is held
+	lk sync.Mutex

 	typ reflect.Type

 	// emitter ref count
 	nEmitters int32

-	// sink index counter
-	sinkC     int
+	keepLast bool
+	last     interface{}

-	// TODO: we could make emit a bit faster by making this into an array, but
-	//  it doesn't seem needed for now
-	sinks  map[int]reflect.Value
+	sinks []chan interface{}
 }

 func newNode(typ reflect.Type) *node {
 	return &node{
 		typ: typ,
-
-		sinks: map[int]reflect.Value{},
 	}
 }

-func (n *node) sub(outChan reflect.Value) int {
-	i := n.sinkC
-	n.sinkC++
-	n.sinks[i] = outChan
-	return i
-}
-
 func (n *node) emit(event interface{}) {
-	eval := reflect.ValueOf(event)
-	if eval.Type() != n.typ {
-		panic(fmt.Sprintf("Emit called with wrong type. expected: %s, got: %s", n.typ, eval.Type()))
+	typ := reflect.TypeOf(event)
+	if typ != n.typ {
+		panic(fmt.Sprintf("Emit called with wrong type. expected: %s, got: %s", n.typ, typ))
+	}
+
+	n.lk.Lock()
+	if n.keepLast {
+		n.last = event
 	}

-	n.lk.RLock()
-	// TODO: try using reflect.Select
 	for _, ch := range n.sinks {
-		ch.Send(eval)
+		ch <- event
 	}
-	n.lk.RUnlock()
+	n.lk.Unlock()
 }
-
-///////////////////////
-// UTILS
-
-func typePath(t reflect.Type) string {
-	return t.PkgPath() + "/" + t.String()
-}
-
-var _ Bus = &bus{}
--- a/basic_test.go
+++ b/basic_test.go
@@ -1,4 +1,4 @@
-package event
+package eventbus

 import (
 	"fmt"
@@ -6,41 +6,61 @@ import (
 	"sync/atomic"
 	"testing"
 	"time"
+
+	"github.com/libp2p/go-libp2p-testing/race"
+	"github.com/stretchr/testify/require"
 )

 type EventA struct{}
 type EventB int

+func getN() int {
+	n := 50000
+	if race.WithRace() {
+		n = 1000
+	}
+	return n
+}
+
 func (EventA) String() string {
 	return "Oh, Hello"
 }

+func TestDefaultSubIsBuffered(t *testing.T) {
+	bus := NewBus()
+	s, err := bus.Subscribe(new(EventA))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if cap(s.(*sub).ch) == 0 {
+		t.Fatalf("without any options subscribe should be buffered. was %d", cap(s.(*sub).ch))
+	}
+}
+
 func TestEmit(t *testing.T) {
 	bus := NewBus()
-	events := make(chan EventA)
-	cancel, err := bus.Subscribe(events)
+	sub, err := bus.Subscribe(new(EventA))
 	if err != nil {
 		t.Fatal(err)
 	}

 	go func() {
-		defer cancel()
-		<-events
+		defer sub.Close()
+		<-sub.Out()
 	}()

-	emit, cancel, err := bus.Emitter(new(EventA))
+	em, err := bus.Emitter(new(EventA))
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer cancel()
+	defer em.Close()

-	emit(EventA{})
+	em.Emit(EventA{})
 }

 func TestSub(t *testing.T) {
 	bus := NewBus()
-	events := make(chan EventB)
-	cancel, err := bus.Subscribe(events)
+	sub, err := bus.Subscribe(new(EventB))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -51,18 +71,18 @@ func TestSub(t *testing.T) {
 	wait.Add(1)

 	go func() {
-		defer cancel()
-		event = <-events
+		defer sub.Close()
+		event = (<-sub.Out()).(EventB)
 		wait.Done()
 	}()

-	emit, cancel, err := bus.Emitter(new(EventB))
+	em, err := bus.Emitter(new(EventB))
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer cancel()
+	defer em.Close()

-	emit(EventB(7))
+	em.Emit(EventB(7))
 	wait.Wait()

 	if event != 7 {
@@ -70,43 +90,61 @@ func TestSub(t *testing.T) {
 	}
 }

+func TestEmitterCount(t *testing.T) {
+	bus := NewBus()
+	c, err := bus.EmitterCount(new(EventB))
+	require.NoError(t, err)
+	require.Equal(t, 0, c)
+
+	em, err := bus.Emitter(new(EventB))
+	defer em.Close()
+	require.NoError(t, err)
+	c, err = bus.EmitterCount(new(EventB))
+	require.Equal(t, 1, c)
+
+	em2, err := bus.Emitter(new(EventB))
+	defer em2.Close()
+	require.NoError(t, err)
+	c, err = bus.EmitterCount(new(EventB))
+	require.Equal(t, 2, c)
+
+	// test for error
+	_, err = bus.EmitterCount(EventA{})
+	require.Error(t, err)
+}
+
 func TestEmitNoSubNoBlock(t *testing.T) {
 	bus := NewBus()

-	emit, cancel, err := bus.Emitter(new(EventA))
+	em, err := bus.Emitter(new(EventA))
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer cancel()
+	defer em.Close()

-	emit(EventA{})
+	em.Emit(EventA{})
 }

 func TestEmitOnClosed(t *testing.T) {
 	bus := NewBus()

-	emit, cancel, err := bus.Emitter(new(EventA))
+	em, err := bus.Emitter(new(EventA))
 	if err != nil {
 		t.Fatal(err)
 	}
-	cancel()
-
-	defer func() {
-		r := recover()
-		if r == nil {
-			t.Errorf("expected panic")
-		}
-		if r.(string) != "emitter is closed" {
-			t.Error("unexpected message")
-		}
-	}()
-
-	emit(EventA{})
+	em.Close()
+	err = em.Emit(EventA{})
+	if err == nil {
+		t.Errorf("expected error")
+	}
+	if err.Error() != "emitter is closed" {
+		t.Error("unexpected message")
+	}
 }

 func TestClosingRaces(t *testing.T) {
-	subs := 50000
-	emits := 50000
+	subs := getN()
+	emits := getN()

 	var wg sync.WaitGroup
 	var lk sync.RWMutex
@@ -121,9 +159,9 @@ func TestClosingRaces(t *testing.T) {
 			lk.RLock()
 			defer lk.RUnlock()

-			cancel, _ := b.Subscribe(make(chan EventA))
+			sub, _ := b.Subscribe(new(EventA))
 			time.Sleep(10 * time.Millisecond)
-			cancel()
+			sub.Close()

 			wg.Done()
 		}()
@@ -133,9 +171,9 @@ func TestClosingRaces(t *testing.T) {
 			lk.RLock()
 			defer lk.RUnlock()

-			_, cancel, _ := b.Emitter(new(EventA))
+			emit, _ := b.Emitter(new(EventA))
 			time.Sleep(10 * time.Millisecond)
-			cancel()
+			emit.Close()

 			wg.Done()
 		}()
@@ -146,7 +184,7 @@ func TestClosingRaces(t *testing.T) {

 	wg.Wait()

-	if len(b.(*bus).nodes) != 0 {
+	if len(b.(*basicBus).nodes) != 0 {
 		t.Error("expected no nodes")
 	}
 }
@@ -156,7 +194,7 @@ func TestSubMany(t *testing.T) {

 	var r int32

-	n := 50000
+	n := getN()
 	var wait sync.WaitGroup
 	var ready sync.WaitGroup
 	wait.Add(n)
@@ -164,39 +202,37 @@ func TestSubMany(t *testing.T) {

 	for i := 0; i < n; i++ {
 		go func() {
-			events := make(chan EventB)
-			cancel, err := bus.Subscribe(events)
+			sub, err := bus.Subscribe(new(EventB))
 			if err != nil {
 				panic(err)
 			}
-			defer cancel()
+			defer sub.Close()

 			ready.Done()
-			atomic.AddInt32(&r, int32(<-events))
+			atomic.AddInt32(&r, int32((<-sub.Out()).(EventB)))
 			wait.Done()
 		}()
 	}

-	emit, cancel, err := bus.Emitter(new(EventB))
+	em, err := bus.Emitter(new(EventB))
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer cancel()
+	defer em.Close()

 	ready.Wait()

-	emit(EventB(7))
+	em.Emit(EventB(7))
 	wait.Wait()

-	if int(r) != 7 * n {
+	if int(r) != 7*n {
 		t.Error("got wrong result")
 	}
 }

 func TestSubType(t *testing.T) {
 	bus := NewBus()
-	events := make(chan fmt.Stringer)
-	cancel, err := bus.Subscribe(events, ForceSubType(new(EventA)))
+	sub, err := bus.Subscribe([]interface{}{new(EventA), new(EventB)})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -207,18 +243,18 @@ func TestSubType(t *testing.T) {
 	wait.Add(1)

 	go func() {
-		defer cancel()
-		event = <-events
+		defer sub.Close()
+		event = (<-sub.Out()).(EventA)
 		wait.Done()
 	}()

-	emit, cancel, err := bus.Emitter(new(EventA))
+	em, err := bus.Emitter(new(EventA))
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer cancel()
+	defer em.Close()

-	emit(EventA{})
+	em.Emit(EventA{})
 	wait.Wait()

 	if event.String() != "Oh, Hello" {
@@ -226,7 +262,119 @@ func TestSubType(t *testing.T) {
 	}
 }

-func testMany(t testing.TB, subs, emits, msgs int) {
+func TestNonStateful(t *testing.T) {
+	bus := NewBus()
+	em, err := bus.Emitter(new(EventB))
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer em.Close()
+
+	sub1, err := bus.Subscribe(new(EventB), BufSize(1))
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer sub1.Close()
+
+	select {
+	case <-sub1.Out():
+		t.Fatal("didn't expect to get an event")
+	default:
+	}
+
+	em.Emit(EventB(1))
+
+	select {
+	case e := <-sub1.Out():
+		if e.(EventB) != 1 {
+			t.Fatal("got wrong event")
+		}
+	default:
+		t.Fatal("expected to get an event")
+	}
+
+	sub2, err := bus.Subscribe(new(EventB), BufSize(1))
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer sub2.Close()
+
+	select {
+	case <-sub2.Out():
+		t.Fatal("didn't expect to get an event")
+	default:
+	}
+}
+
+func TestStateful(t *testing.T) {
+	bus := NewBus()
+	em, err := bus.Emitter(new(EventB), Stateful)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer em.Close()
+
+	em.Emit(EventB(2))
+
+	sub, err := bus.Subscribe(new(EventB), BufSize(1))
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer sub.Close()
+
+	if (<-sub.Out()).(EventB) != 2 {
+		t.Fatal("got wrong event")
+	}
+}
+
+func TestCloseBlocking(t *testing.T) {
+	bus := NewBus()
+	em, err := bus.Emitter(new(EventB))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	sub, err := bus.Subscribe(new(EventB))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	go func() {
+		em.Emit(EventB(159))
+	}()
+
+	time.Sleep(10 * time.Millisecond) // make sure that emit is blocked
+
+	sub.Close() // cancel sub
+}
+
+func panicOnTimeout(d time.Duration) {
+	<-time.After(d)
+	panic("timeout reached")
+}
+
+func TestSubFailFully(t *testing.T) {
+	bus := NewBus()
+	em, err := bus.Emitter(new(EventB))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = bus.Subscribe([]interface{}{new(EventB), 5})
+	if err == nil || err.Error() != "subscribe called with non-pointer type" {
+		t.Fatal(err)
+	}
+
+	go panicOnTimeout(5 * time.Second)
+
+	em.Emit(EventB(159)) // will hang if sub doesn't fail properly
+}
+
+func testMany(t testing.TB, subs, emits, msgs int, stateful bool) {
+	if race.WithRace() && subs+emits > 5000 {
+		t.SkipNow()
+	}
+
 	bus := NewBus()

 	var r int64
@@ -238,16 +386,19 @@ func testMany(t testing.TB, subs, emits, msgs int) {

 	for i := 0; i < subs; i++ {
 		go func() {
-			events := make(chan EventB)
-			cancel, err := bus.Subscribe(events)
+			sub, err := bus.Subscribe(new(EventB))
 			if err != nil {
 				panic(err)
 			}
-			defer cancel()
+			defer sub.Close()

 			ready.Done()
-			for i := 0; i < emits * msgs; i++ {
-				atomic.AddInt64(&r, int64(<-events))
+			for i := 0; i < emits*msgs; i++ {
+				e, ok := <-sub.Out()
+				if !ok {
+					panic("wat")
+				}
+				atomic.AddInt64(&r, int64(e.(EventB)))
 			}
 			wait.Done()
 		}()
@@ -255,16 +406,19 @@ func testMany(t testing.TB, subs, emits, msgs int) {

 	for i := 0; i < emits; i++ {
 		go func() {
-			emit, cancel, err := bus.Emitter(new(EventB))
+			em, err := bus.Emitter(new(EventB), func(settings interface{}) error {
+				settings.(*emitterSettings).makeStateful = stateful
+				return nil
+			})
 			if err != nil {
 				panic(err)
 			}
-			defer cancel()
+			defer em.Close()

 			ready.Wait()

 			for i := 0; i < msgs; i++ {
-				emit(EventB(97))
+				em.Emit(EventB(97))
 			}

 			wait.Done()
@@ -273,66 +427,131 @@ func testMany(t testing.TB, subs, emits, msgs int) {

 	wait.Wait()

-	if int(r) != 97 * subs * emits * msgs {
+	if int(r) != 97*subs*emits*msgs {
 		t.Fatal("got wrong result")
 	}
 }

 func TestBothMany(t *testing.T) {
-	testMany(t, 10000, 100, 10)
+	testMany(t, 10000, 100, 10, false)
 }

-func BenchmarkSubs(b *testing.B) {
-	b.ReportAllocs()
-	testMany(b, b.N, 100, 100)
+type benchCase struct {
+	subs     int
+	emits    int
+	stateful bool
 }

-func BenchmarkEmits(b *testing.B) {
-	b.ReportAllocs()
-	testMany(b, 100, b.N, 100)
+func (bc benchCase) name() string {
+	return fmt.Sprintf("subs-%03d/emits-%03d/stateful-%t", bc.subs, bc.emits, bc.stateful)
 }

-func BenchmarkMsgs(b *testing.B) {
-	b.ReportAllocs()
-	testMany(b, 100, 100, b.N)
+func genTestCases() []benchCase {
+	ret := make([]benchCase, 0, 200)
+	for stateful := 0; stateful < 2; stateful++ {
+		for subs := uint(0); subs <= 8; subs = subs + 4 {
+			for emits := uint(0); emits <= 8; emits = emits + 4 {
+				ret = append(ret, benchCase{1 << subs, 1 << emits, stateful == 1})
+			}
+		}
+	}
+	return ret
 }

-func BenchmarkOneToMany(b *testing.B) {
-	b.ReportAllocs()
-	testMany(b, b.N, 1, 100)
+func BenchmarkEvents(b *testing.B) {
+	for _, bc := range genTestCases() {
+		b.Run(bc.name(), benchMany(bc))
+	}
 }

-func BenchmarkManyToOne(b *testing.B) {
-	b.ReportAllocs()
-	testMany(b, 1, b.N, 100)
+func benchMany(bc benchCase) func(*testing.B) {
+	return func(b *testing.B) {
+		b.ReportAllocs()
+		subs := bc.subs
+		emits := bc.emits
+		stateful := bc.stateful
+		bus := NewBus()
+		var wait sync.WaitGroup
+		var ready sync.WaitGroup
+		wait.Add(subs + emits)
+		ready.Add(subs + emits)
+
+		for i := 0; i < subs; i++ {
+			go func() {
+				sub, err := bus.Subscribe(new(EventB))
+				if err != nil {
+					panic(err)
+				}
+				defer sub.Close()
+
+				ready.Done()
+				ready.Wait()
+				for i := 0; i < (b.N/emits)*emits; i++ {
+					_, ok := <-sub.Out()
+					if !ok {
+						panic("wat")
+					}
+				}
+				wait.Done()
+			}()
+		}
+
+		for i := 0; i < emits; i++ {
+			go func() {
+				em, err := bus.Emitter(new(EventB), func(settings interface{}) error {
+					settings.(*emitterSettings).makeStateful = stateful
+					return nil
+				})
+				if err != nil {
+					panic(err)
+				}
+				defer em.Close()
+
+				ready.Done()
+				ready.Wait()
+
+				for i := 0; i < b.N/emits; i++ {
+					em.Emit(EventB(97))
+				}
+
+				wait.Done()
+			}()
+		}
+		ready.Wait()
+		b.ResetTimer()
+		wait.Wait()
+	}
 }

-func BenchmarkMs1e2m4(b *testing.B) {
-	b.N = 1000000
+var div = 100
+
+func BenchmarkSubscribe(b *testing.B) {
 	b.ReportAllocs()
-	testMany(b, 10, 100, 10000)
+	for i := 0; i < b.N/div; i++ {
+		bus := NewBus()
+		for j := 0; j < div; j++ {
+			bus.Subscribe(new(EventA))
+		}
+	}
 }

-func BenchmarkMs1e0m6(b *testing.B) {
-	b.N = 10000000
+func BenchmarkEmitter(b *testing.B) {
 	b.ReportAllocs()
-	testMany(b, 10, 1, 1000000)
+	for i := 0; i < b.N/div; i++ {
+		bus := NewBus()
+		for j := 0; j < div; j++ {
+			bus.Emitter(new(EventA))
+		}
+	}
 }

-func BenchmarkMs0e0m6(b *testing.B) {
-	b.N = 1000000
+func BenchmarkSubscribeAndEmitter(b *testing.B) {
 	b.ReportAllocs()
-	testMany(b, 1, 1, 1000000)
-}
-
-func BenchmarkMs0e6m0(b *testing.B) {
-	b.N = 1000000
-	b.ReportAllocs()
-	testMany(b, 1, 1000000, 1)
-}
-
-func BenchmarkMs6e0m0(b *testing.B) {
-	b.N = 1000000
-	b.ReportAllocs()
-	testMany(b, 1000000, 1, 1)
+	for i := 0; i < b.N/div; i++ {
+		bus := NewBus()
+		for j := 0; j < div; j++ {
+			bus.Subscribe(new(EventA))
+			bus.Emitter(new(EventA))
+		}
+	}
 }
--- a/codecov.yml
+++ b/codecov.yml
@@ -0,0 +1,3 @@
+coverage:
+  range: "50...100"
+comment: off
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,9 @@
 module github.com/libp2p/go-eventbus

 go 1.12
+
+require (
+	github.com/libp2p/go-libp2p-core v0.5.1-0.20200326052016-dc8b8fa8c504
+	github.com/libp2p/go-libp2p-testing v0.1.1
+	github.com/stretchr/testify v1.4.0
+)
--- a/go.sum
+++ b/go.sum
@@ -0,0 +1,229 @@
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--- a/interface.go
+++ b/interface.go
@@ -1,50 +0,0 @@
-package event
-
-import (
-	"errors"
-	"reflect"
-)
-
-type SubSettings struct {
-	forcedType reflect.Type
-}
-type SubOption func(*SubSettings) error
-
-func ForceSubType(evtType interface{}) SubOption {
-	return func(s *SubSettings) error {
-		typ := reflect.TypeOf(evtType)
-		if typ.Kind() != reflect.Ptr {
-			return errors.New("ForceSubType called with non-pointer type")
-		}
-		s.forcedType = typ
-		return nil
-	}
-}
-
-type EmitterSettings struct {}
-type EmitterOption func(*EmitterSettings)
-
-type Bus interface {
-	// Subscribe creates new subscription. Failing to drain the incoming channel
-	// will cause publishers to get blocked
-	//
-	// evtTypes only accepts typed nil pointers, and uses the type information to
-	// select output type
-	//
-	// Example:
-	// sub, cancel, err := eventbus.Subscribe(new(os.Signal))
-	// defer cancel()
-	//
-	// evt := (<-sub).(os.Signal) // guaranteed to be safe
-	Subscribe(typedChan interface{}, opts ...SubOption) (CancelFunc, error)
-
-	Emitter(eventType interface{}, opts ...EmitterOption) (EmitFunc, CancelFunc, error)
-}
-
-// EmitFunc emits events. If any channel subscribed to the topic is blocked,
-// calls to EmitFunc will block
-//
-// Calling this function with wrong event type will cause a panic
-type EmitFunc func(event interface{})
-
-type CancelFunc func()
--- a/opts.go
+++ b/opts.go
@@ -0,0 +1,32 @@
+package eventbus
+
+type subSettings struct {
+	buffer int
+}
+
+var subSettingsDefault = subSettings{
+	buffer: 16,
+}
+
+func BufSize(n int) func(interface{}) error {
+	return func(s interface{}) error {
+		s.(*subSettings).buffer = n
+		return nil
+	}
+}
+
+type emitterSettings struct {
+	makeStateful bool
+}
+
+// Stateful is an Emitter option which makes makes the eventbus channel
+// 'remember' last event sent, and when a new subscriber joins the
+// bus, the remembered event is immediately sent to the subscription
+// channel.
+//
+// This allows to provide state tracking for dynamic systems, and/or
+// allows new subscribers to verify that there are Emitters on the channel
+func Stateful(s interface{}) error {
+	s.(*emitterSettings).makeStateful = true
+	return nil
+}
Author	SHA1	Message	Date
Aarsh Shah	c30c9409b9	add the emitter count method to the bus	2020-03-26 10:53:55 +05:30
Steven Allen	5e53d8f064	Merge pull request #28 from libp2p/dependabot/go_modules/github.com/libp2p/go-libp2p-core-0.5.0 Bump github.com/libp2p/go-libp2p-core from 0.3.0 to 0.5.0	2020-03-11 11:48:10 -07:00
dependabot-preview[bot]	258b78fa88	Bump github.com/libp2p/go-libp2p-core from 0.3.0 to 0.5.0 Bumps [github.com/libp2p/go-libp2p-core](https://github.com/libp2p/go-libp2p-core) from 0.3.0 to 0.5.0. - [Release notes](https://github.com/libp2p/go-libp2p-core/releases) - [Commits](https://github.com/libp2p/go-libp2p-core/compare/v0.3.0...v0.5.0) Signed-off-by: dependabot-preview[bot] <support@dependabot.com>	2020-03-09 11:18:09 +00:00
Steven Allen	ff9925e51f	Merge pull request #25 from libp2p/dependabot/go_modules/github.com/libp2p/go-libp2p-core-0.3.0 Bump github.com/libp2p/go-libp2p-core from 0.2.5 to 0.3.0	2019-12-17 12:46:43 +01:00
dependabot-preview[bot]	0e3045bb10	Bump github.com/libp2p/go-libp2p-core from 0.2.5 to 0.3.0 Bumps [github.com/libp2p/go-libp2p-core](https://github.com/libp2p/go-libp2p-core) from 0.2.5 to 0.3.0. - [Release notes](https://github.com/libp2p/go-libp2p-core/releases) - [Commits](https://github.com/libp2p/go-libp2p-core/compare/v0.2.5...v0.3.0) Signed-off-by: dependabot-preview[bot] <support@dependabot.com>	2019-12-12 11:19:39 +00:00
Steven Allen	8ae18d1356	Merge pull request #23 from libp2p/dependabot/go_modules/github.com/libp2p/go-libp2p-core-0.2.5 Bump github.com/libp2p/go-libp2p-core from 0.2.2 to 0.2.5	2019-12-06 20:13:11 -05:00
dependabot-preview[bot]	11999efa2d	Bump github.com/libp2p/go-libp2p-core from 0.2.2 to 0.2.5 Bumps [github.com/libp2p/go-libp2p-core](https://github.com/libp2p/go-libp2p-core) from 0.2.2 to 0.2.5. - [Release notes](https://github.com/libp2p/go-libp2p-core/releases) - [Commits](https://github.com/libp2p/go-libp2p-core/compare/v0.2.2...v0.2.5) Signed-off-by: dependabot-preview[bot] <support@dependabot.com>	2019-12-07 01:09:51 +00:00
Steven Allen	e358464c5b	Merge pull request #22 from libp2p/dependabot/go_modules/github.com/libp2p/go-libp2p-testing-0.1.1 Bump github.com/libp2p/go-libp2p-testing from 0.0.4 to 0.1.1	2019-12-06 20:07:30 -05:00
Steven Allen	0a84ebcf30	Merge pull request #24 from libp2p/ci/go-1.13 ci: bump go to 1.13	2019-12-06 16:56:17 -05:00
Steven Allen	0f2b217368	ci: bump to go 1.13	2019-12-06 16:30:18 -05:00
dependabot-preview[bot]	2a09bc5311	Bump github.com/libp2p/go-libp2p-testing from 0.0.4 to 0.1.1 Bumps [github.com/libp2p/go-libp2p-testing](https://github.com/libp2p/go-libp2p-testing) from 0.0.4 to 0.1.1. - [Release notes](https://github.com/libp2p/go-libp2p-testing/releases) - [Commits](https://github.com/libp2p/go-libp2p-testing/compare/v0.0.4...v0.1.1) Signed-off-by: dependabot-preview[bot] <support@dependabot.com>	2019-12-06 17:40:46 +00:00
bigs	d34a18eba2	Merge pull request #21 from libp2p/bug/panic-after-close [DEPENDENT MERGE] Return error rather than panic in Emit	2019-08-06 16:48:00 -04:00
Cole Brown	7c7260c6f3	Bump go-libp2p-core	2019-08-06 16:37:00 -04:00
bigs	40251732b1	Update test error message Co-Authored-By: Łukasz Magiera <magik6k@users.noreply.github.com>	2019-08-01 09:38:57 -08:00
Cole Brown	217da8e826	Return error when closing already closed emitter	2019-07-31 19:46:51 -04:00
Cole Brown	b1629519a0	Return error rather than panic in Emit	2019-07-30 15:51:57 -04:00
Łukasz Magiera	4afad1f620	Merge pull request #17 from libp2p/fix/with-node nit: fix with-node	2019-06-28 00:40:03 +02:00
Łukasz Magiera	d88ec38bc6	Merge pull request #19 from libp2p/fix/16 fix: serialize publishing	2019-06-28 00:38:22 +02:00
Steven Allen	25d54bbbec	fix: serialize publishing Ensure that all subscribers see events in the same order. This also ensures that the subscribers never see the initial "latest" event after some other event. fixes #16	2019-06-27 22:34:44 +02:00
Łukasz Magiera	04058af20a	Merge pull request #18 from libp2p/fix/fully-drain fix: completely drain on close	2019-06-27 22:15:01 +02:00
Steven Allen	a77f09c820	fix: completely drain on close Issue: We could partially drain and end up with, e.g., a close event missing a matching open event.	2019-06-27 20:17:04 +02:00
Steven Allen	7b280b5c1b	nit: fix with-node 1. It doesn't return an error and we weren't checking it anyways. 2. Avoid a goroutine unless we need it.	2019-06-27 20:13:36 +02:00
Steven Allen	df5be7d7dd	Merge pull request #11 from libp2p/fix/things Fix close deadlock and Sub type error	2019-06-27 20:13:09 +02:00
Łukasz Magiera	0c299185af	Merge pull request #14 from libp2p/nit/simple-reflect nit: avoid ValueOf	2019-06-27 19:40:02 +02:00
Steven Allen	12782426ed	nit: avoid ValueOf We only need TypeOf.	2019-06-27 19:20:43 +02:00
Łukasz Magiera	9c3fe0580a	Merge pull request #13 from libp2p/feat/buffer-by-default Enable buffering by default	2019-06-25 22:07:48 +02:00
Jakub Sztandera	0976d4b358	Enable buffering by default License: MIT Signed-off-by: Jakub Sztandera <kubuxu@protonmail.ch>	2019-06-25 20:47:02 +02:00
Łukasz Magiera	61257f90a2	Merge pull request #12 from libp2p/feat/better-bench Improve benchmarks	2019-06-22 17:41:26 +02:00
Jakub Sztandera	85cd6aa7c7	Add benchmarks for subscribe and emitter License: MIT Signed-off-by: Jakub Sztandera <kubuxu@protonmail.ch>	2019-06-22 17:39:16 +02:00
Jakub Sztandera	fc8fa53d99	Clean up format License: MIT Signed-off-by: Jakub Sztandera <kubuxu@protonmail.ch>	2019-06-22 15:50:30 +02:00
Jakub Sztandera	facb8f2fed	Reduce number of samples License: MIT Signed-off-by: Jakub Sztandera <kubuxu@protonmail.ch>	2019-06-22 15:48:06 +02:00
Jakub Sztandera	454cbe5497	Make the test fail in reasonable time License: MIT Signed-off-by: Jakub Sztandera <kubuxu@protonmail.ch>	2019-06-22 15:45:09 +02:00
Jakub Sztandera	d2cb2a10b6	Improve benchmarks License: MIT Signed-off-by: Jakub Sztandera <kubuxu@protonmail.ch>	2019-06-22 15:30:12 +02:00
Łukasz Magiera	3fd76c7eac	Add test for #10	2019-06-22 15:14:04 +02:00
Łukasz Magiera	525a0e67fe	fix close deadlock and Sub type error	2019-06-22 12:05:03 +02:00
Łukasz Magiera	6212a929bf	refactor interfaces (#9 )	2019-06-21 17:50:36 +01:00
Raúl Kripalani	f100eac4ef	Refinements before first release 🎉 (#7 )	2019-06-20 16:17:57 +01:00
Raúl Kripalani	c7aefba960	update go-libp2p-core dep.	2019-06-20 00:01:35 +01:00
Raúl Kripalani	fe6d9d1489	rename eventbus package. (#4 )	2019-06-19 16:55:25 +01:00
Łukasz Magiera	131418619d	Merge pull request #1 from libp2p/feat/implement Implement	2019-06-19 17:32:27 +02:00
Raúl Kripalani	015ba825e9	fix compile error in tests.	2019-06-19 16:21:55 +01:00
Raúl Kripalani	8b7b645962	remove superfluous types.	2019-06-19 16:13:28 +01:00
Raúl Kripalani	bd8289f870	make Emitter an interface.	2019-06-19 16:10:03 +01:00
Łukasz Magiera	1ab671b0ca	Merge pull request #2 from libp2p/ci/enable ci: enable	2019-06-19 16:04:46 +02:00
Łukasz Magiera	a1807fd415	Drop the interface	2019-06-19 15:36:31 +02:00
Łukasz Magiera	2341c42dab	Merge pull request #3 from libp2p/feat/interface generify options.	2019-06-19 15:13:27 +02:00
Raúl Kripalani	2ea3b26fbd	generify options.	2019-06-19 14:09:12 +01:00
Łukasz Magiera	04b7ec33de	BasicBus to basicBus	2019-06-19 15:00:22 +02:00
Łukasz Magiera	401bb25f47	return struct from NewBus	2019-06-19 14:48:41 +02:00
Łukasz Magiera	2f028f9607	Update Emitter docs	2019-06-19 14:32:55 +02:00
Łukasz Magiera	942c134291	Move close to EmitFunc	2019-06-19 14:27:37 +02:00
Łukasz Magiera	d23aaa9b5c	Address @stebalien's review	2019-06-19 14:22:10 +02:00
Łukasz Magiera	1cb839f3b0	Document options	2019-06-19 14:13:48 +02:00
Steven Allen	3abafaf475	ci: enable	2019-06-19 14:12:41 +02:00
Łukasz Magiera	71ffb0ebf1	Use reflect.Type in node map	2019-06-19 13:51:25 +02:00
Łukasz Magiera	8b50ba1149	Some more docs	2019-06-19 12:46:59 +02:00
Łukasz Magiera	c54e8ebbe9	Simplify withNode a bit	2019-06-19 12:31:36 +02:00
Łukasz Magiera	5b845983c2	Fix data races	2019-06-19 12:13:18 +02:00
Łukasz Magiera	287e2189af	Stateful emits	2019-06-16 21:42:47 +02:00
Jakub Sztandera	821aef1f4b	Use slice instead of map License: MIT Signed-off-by: Jakub Sztandera <kubuxu@protonmail.ch>	2019-06-16 19:20:10 +02:00
Łukasz Magiera	1c855d2c2d	Gofmt	2019-06-16 19:20:10 +02:00