Support wildcard subscriptions + getter for known types (optimized) (#40)

Co-authored-by: Raúl Kripalani <raul@protocol.ai>

.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

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
 

basic.go

@@ -1,4 +1,4 @@
-package event
+package eventbus
 
 import (
 	"errors"
@@ -6,144 +6,317 @@ 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.RWMutex
+	nodes    map[reflect.Type]*node
+	wildcard *wildcardNode
 }
 
-func NewBus() Bus {
-	return &bus{
-		nodes: map[string]*node{},
+var _ event.Bus = (*basicBus)(nil)
+
+type emitter struct {
+	n       *node
+	w       *wildcardNode
+	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)
+	e.w.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{},
+		wildcard: new(wildcardNode),
 	}
 }
 
-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 wildcardSub struct {
+	ch chan interface{}
+	w  *wildcardNode
+}
+
+func (w *wildcardSub) Out() <-chan interface{} {
+	return w.ch
+}
+
+func (w *wildcardSub) Close() error {
+	w.w.removeSink(w.ch)
+	return nil
+}
+
+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 := 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")
-	}
-
-	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)
+	if evtTypes == event.WildcardSubscription {
+		out := &wildcardSub{
+			ch: make(chan interface{}, settings.buffer),
+			w:  b.wildcard,
 		}
-		typ = settings.forcedType
+		b.wildcard.addSink(out.ch)
+		return out, nil
 	}
 
-	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
-		n.sub(refCh)
+	types, ok := evtTypes.([]interface{})
+	if !ok {
+		types = []interface{}{evtTypes}
+	}
 
-		c = func() {
-			n.lk.Lock()
-			for i := 0; i < len(n.sinks); i++ {
-				if n.sinks[i] == refCh {
-					n.sinks[i] = n.sinks[len(n.sinks)-1]
-					n.sinks = n.sinks[:len(n.sinks)-1]
-					break
+	if len(types) > 1 {
+		for _, t := range types {
+			if t == event.WildcardSubscription {
+				return nil, fmt.Errorf("wildcard subscriptions must be started separately")
+			}
+		}
+	}
+
+	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")
+		}
+	}
+
+	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
 			}
-			tryDrop := len(n.sinks) == 0 && n.nEmitters == 0
-			n.lk.Unlock()
-			if tryDrop {
-				b.tryDropNode(typ.Elem())
-			}
-		}
-	})
-	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) {
+	if evtType == event.WildcardSubscription {
+		return nil, fmt.Errorf("illegal emitter for wildcard subscription")
+	}
+
+	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, w: b.wildcard}
+	}, nil)
 	return
 }
 
+// GetAllEventTypes returns all the event types that this bus has emitters
+// or subscribers for.
+func (b *basicBus) GetAllEventTypes() []reflect.Type {
+	b.lk.RLock()
+	defer b.lk.RUnlock()
+
+	types := make([]reflect.Type, 0, len(b.nodes))
+	for t, _ := range b.nodes {
+		types = append(types, t)
+	}
+	return types
+}
+
 ///////////////////////
 // NODE
 
+type wildcardNode struct {
+	sync.RWMutex
+	nSinks int32
+	sinks  []chan interface{}
+}
+
+func (n *wildcardNode) addSink(ch chan interface{}) {
+	atomic.AddInt32(&n.nSinks, 1) // ok to do outside the lock
+	n.Lock()
+	n.sinks = append(n.sinks, ch)
+	n.Unlock()
+}
+
+func (n *wildcardNode) removeSink(ch chan interface{}) {
+	atomic.AddInt32(&n.nSinks, -1) // ok to do outside the lock
+	n.Lock()
+	for i := 0; i < len(n.sinks); i++ {
+		if n.sinks[i] == 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
+		}
+	}
+	n.Unlock()
+}
+
+func (n *wildcardNode) emit(evt interface{}) {
+	if atomic.LoadInt32(&n.nSinks) == 0 {
+		return
+	}
+
+	n.RLock()
+	for _, ch := range n.sinks {
+		ch <- evt
+	}
+	n.RUnlock()
+}
+
 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
 
@@ -151,9 +324,9 @@ type node struct {
 	nEmitters int32
 
 	keepLast bool
-	last     reflect.Value
+	last     interface{}
 
-	sinks []reflect.Value
+	sinks []chan interface{}
 }
 
 func newNode(typ reflect.Type) *node {
@@ -162,29 +335,19 @@ func newNode(typ reflect.Type) *node {
 	}
 }
 
-func (n *node) sub(outChan reflect.Value) {
-	n.sinks = append(n.sinks, outChan)
-}
-
-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()))
+func (n *node) emit(evt interface{}) {
+	typ := reflect.TypeOf(evt)
+	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 = evt
 	}
 
-	n.lk.RLock()
-	// TODO: try using reflect.Select
 	for _, ch := range n.sinks {
-		ch.Send(eval)
+		ch <- evt
 	}
-	n.lk.RUnlock()
+	n.lk.Unlock()
 }
-
-///////////////////////
-// UTILS
-
-func typePath(t reflect.Type) string {
-	return t.PkgPath() + "/" + t.String()
-}
-
-var _ Bus = &bus{}

basic_test.go

@@ -1,46 +1,70 @@
-package event
+package eventbus
 
 import (
+	"context"
 	"fmt"
+	"reflect"
 	"sync"
 	"sync/atomic"
 	"testing"
 	"time"
+
+	"github.com/libp2p/go-libp2p-core/event"
+	"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 +75,18 @@ 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 +94,62 @@ func TestSub(t *testing.T) {
 	}
 }
 
+func TestGetAllEventTypes(t *testing.T) {
+	bus := NewBus()
+	require.Empty(t, bus.GetAllEventTypes())
+
+	// the wildcard subscription should be returned.
+	_, err := bus.Subscribe(event.WildcardSubscription)
+	require.NoError(t, err)
+
+	_, err = bus.Subscribe(new(EventB))
+	require.NoError(t, err)
+
+	evts := bus.GetAllEventTypes()
+	require.Len(t, evts, 1)
+	require.Equal(t, reflect.TypeOf((*EventB)(nil)).Elem(), evts[0])
+
+	_, err = bus.Emitter(new(EventA))
+	require.NoError(t, err)
+
+	evts = bus.GetAllEventTypes()
+	require.Len(t, evts, 2)
+	require.Contains(t, evts, reflect.TypeOf((*EventB)(nil)).Elem())
+	require.Contains(t, evts, reflect.TypeOf((*EventA)(nil)).Elem())
+}
+
 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 +164,9 @@ 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 +176,9 @@ 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 +189,7 @@ 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 +199,7 @@ func TestSubMany(t *testing.T) {
 
 	var r int32
 
-	n := 50000
+	n := getN()
 	var wait sync.WaitGroup
 	var ready sync.WaitGroup
 	wait.Add(n)
@@ -164,28 +207,27 @@ 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 {
@@ -193,10 +235,111 @@ func TestSubMany(t *testing.T) {
 	}
 }
 
+func TestWildcardSubscription(t *testing.T) {
+	bus := NewBus()
+	sub, err := bus.Subscribe(event.WildcardSubscription)
+	require.NoError(t, err)
+	defer sub.Close()
+
+	em1, err := bus.Emitter(new(EventA))
+	require.NoError(t, err)
+	defer em1.Close()
+
+	em2, err := bus.Emitter(new(EventB))
+	require.NoError(t, err)
+	defer em2.Close()
+
+	require.NoError(t, em1.Emit(EventA{}))
+	require.NoError(t, em2.Emit(EventB(1)))
+
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	var evts []interface{}
+
+LOOP:
+	for {
+		select {
+		case evt := <-sub.Out():
+			if evta, ok := evt.(EventA); ok {
+				evts = append(evts, evta)
+			}
+
+			if evtb, ok := evt.(EventB); ok {
+				evts = append(evts, evtb)
+			}
+
+			if len(evts) == 2 {
+				break LOOP
+			}
+
+		case <-ctx.Done():
+			t.Fatalf("did not receive events")
+		}
+	}
+}
+
+func TestManyWildcardSubscriptions(t *testing.T) {
+	bus := NewBus()
+	var subs []event.Subscription
+	for i := 0; i < 10; i++ {
+		sub, err := bus.Subscribe(event.WildcardSubscription)
+		require.NoError(t, err)
+		subs = append(subs, sub)
+	}
+
+	em1, err := bus.Emitter(new(EventA))
+	require.NoError(t, err)
+	defer em1.Close()
+
+	em2, err := bus.Emitter(new(EventB))
+	require.NoError(t, err)
+	defer em2.Close()
+
+	require.NoError(t, em1.Emit(EventA{}))
+	require.NoError(t, em2.Emit(EventB(1)))
+
+	// all 10 subscriptions received all 2 events.
+	for _, s := range subs {
+		require.Len(t, s.Out(), 2)
+	}
+
+	// close the first five subscriptions.
+	for _, s := range subs[:5] {
+		require.NoError(t, s.Close())
+	}
+
+	// emit another 2 events.
+	require.NoError(t, em1.Emit(EventA{}))
+	require.NoError(t, em2.Emit(EventB(1)))
+
+	// the first five still have 2 events, while the other five have 4 events.
+	for _, s := range subs[:5] {
+		require.Len(t, s.Out(), 2)
+	}
+
+	for _, s := range subs[5:] {
+		require.Len(t, s.Out(), 4)
+	}
+
+	// close them all, the first five will be closed twice (asserts idempotency).
+	for _, s := range subs {
+		require.NoError(t, s.Close())
+	}
+}
+
+func TestWildcardValidations(t *testing.T) {
+	bus := NewBus()
+
+	_, err := bus.Subscribe([]interface{}{event.WildcardSubscription, new(EventA), new(EventB)})
+	require.Error(t, err)
+
+	_, err = bus.Emitter(event.WildcardSubscription)
+	require.Error(t, err)
+}
+
 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 +350,18 @@ 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 +369,119 @@ 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 +493,19 @@ 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))
+				e, ok := <-sub.Out()
+				if !ok {
+					panic("wat")
+				}
+				atomic.AddInt64(&r, int64(e.(EventB)))
 			}
 			wait.Done()
 		}()
@@ -255,16 +513,19 @@ 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()
@@ -279,72 +540,125 @@ func testMany(t testing.TB, subs, emits, msgs int) {
 }
 
 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 BenchmarkOneToMany(b *testing.B) {
-	b.ReportAllocs()
-	testMany(b, b.N, 1, 100)
-}
-
-func BenchmarkManyToOne(b *testing.B) {
-	b.ReportAllocs()
-	testMany(b, 1, b.N, 100)
-}
-
-func BenchmarkMs1e2m4(b *testing.B) {
-	b.N = 1000000
-	b.ReportAllocs()
-	testMany(b, 10, 100, 10000)
-}
-
-func BenchmarkMs1e0m6(b *testing.B) {
-	b.N = 10000000
-	b.ReportAllocs()
-	testMany(b, 10, 1, 1000000)
-}
-
-func BenchmarkMs0e0m6(b *testing.B) {
-	b.N = 1000000
-	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)
-}
-
-func t() {
-	bus := NewBus()
-
-	events := make(chan fmt.Stringer)
-	cancel, err := bus.Subscribe(events, Stateful)
-	if err != nil {
-		//
+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 BenchmarkEvents(b *testing.B) {
+	for _, bc := range genTestCases() {
+		b.Run(bc.name(), benchMany(bc))
+	}
+}
+
+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()
+	}
+}
+
+var div = 100
+
+func BenchmarkSubscribe(b *testing.B) {
+	b.ReportAllocs()
+	for i := 0; i < b.N/div; i++ {
+		bus := NewBus()
+		for j := 0; j < div; j++ {
+			bus.Subscribe(new(EventA))
+		}
+	}
+}
+
+func BenchmarkEmitter(b *testing.B) {
+	b.ReportAllocs()
+	for i := 0; i < b.N/div; i++ {
+		bus := NewBus()
+		for j := 0; j < div; j++ {
+			bus.Emitter(new(EventA))
+		}
+	}
+}
+
+func BenchmarkSubscribeAndEmitter(b *testing.B) {
+	b.ReportAllocs()
+	for i := 0; i < b.N/div; i++ {
+		bus := NewBus()
+		for j := 0; j < div; j++ {
+			bus.Subscribe(new(EventA))
+			bus.Emitter(new(EventA))
+		}
 	}
-	defer cancel()
-
 }

codecov.yml

@@ -0,0 +1,3 @@
+coverage:
+  range: "50...100"
+comment: off

go.mod

@@ -1,3 +1,9 @@
 module github.com/libp2p/go-eventbus
 
 go 1.12
+
+require (
+	github.com/libp2p/go-libp2p-core v0.5.7-0.20200520143746-39497bae12c5
+	github.com/libp2p/go-libp2p-testing v0.1.1
+	github.com/stretchr/testify v1.4.0
+)

go.sum

@@ -0,0 +1,177 @@
+cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
+github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
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+github.com/btcsuite/btcd v0.20.1-beta h1:Ik4hyJqN8Jfyv3S4AGBOmyouMsYE3EdYODkMbQjwPGw=
+github.com/btcsuite/btcd v0.20.1-beta/go.mod h1:wVuoA8VJLEcwgqHBwHmzLRazpKxTv13Px/pDuV7OomQ=
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+gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=

interface.go

@@ -1,49 +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 channel will cause
-	// publishers to get blocked
-	Subscribe(typedChan interface{}, opts ...SubOption) (CancelFunc, error)
-
-	// Emitter creates new emitter
-	//
-	// eventType accepts typed nil pointers, and uses the type information to
-	// select output type
-	//
-	// Example:
-	// sub, cancel, err := eventbus.Subscribe(new(os.Signal))
-	// defer cancel()
-	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()

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
+}