Merge pull request #56 from fjl/feature/raceless-eventer

Fix Eventer race

eventer/eventer.go

 package eventer
 
+import "sync"
+
 // Basic receiver interface.
 type Receiver interface {
 	Send(Event)
@@ -27,17 +29,18 @@ type Event struct {
 type Channels map[string][]Receiver
 
 type EventMachine struct {
+	mu       sync.RWMutex
 	channels Channels
 }
 
 func New() *EventMachine {
-	return &EventMachine{
-		channels: make(Channels),
-	}
+	return &EventMachine{channels: make(Channels)}
 }
 
 func (self *EventMachine) add(typ string, r Receiver) {
+	self.mu.Lock()
 	self.channels[typ] = append(self.channels[typ], r)
+	self.mu.Unlock()
 }
 
 // Generalised methods for the known receiver types
@@ -64,11 +67,11 @@ func (self *EventMachine) RegisterFunc(typ string, f Function) {
 func (self *EventMachine) Register(typ string) Channel {
 	c := make(Channel, 1)
 	self.add(typ, c)
-
 	return c
 }
 
 func (self *EventMachine) Post(typ string, data interface{}) {
+	self.mu.RLock()
 	if self.channels[typ] != nil {
 		ev := Event{typ, data}
 		for _, receiver := range self.channels[typ] {
@@ -76,4 +79,5 @@ func (self *EventMachine) Post(typ string, data interface{}) {
 			receiver.Send(ev)
 		}
 	}
+	self.mu.RUnlock()
 }

eventer/eventer_test.go

 package eventer
 
-import "testing"
+import (
+	"math/rand"
+	"testing"
+	"time"
+)
 
 func TestChannel(t *testing.T) {
-	eventer := New(nil)
+	eventer := New()
 
 	c := make(Channel, 1)
 	eventer.RegisterChannel("test", c)
@@ -17,7 +21,7 @@ func TestChannel(t *testing.T) {
 }
 
 func TestFunction(t *testing.T) {
-	eventer := New(nil)
+	eventer := New()
 
 	var data string
 	eventer.RegisterFunc("test", func(ev Event) {
@@ -31,7 +35,7 @@ func TestFunction(t *testing.T) {
 }
 
 func TestRegister(t *testing.T) {
-	eventer := New(nil)
+	eventer := New()
 
 	c := eventer.Register("test")
 	eventer.Post("test", "hello world")
@@ -44,7 +48,7 @@ func TestRegister(t *testing.T) {
 }
 
 func TestOn(t *testing.T) {
-	eventer := New(nil)
+	eventer := New()
 
 	c := make(Channel, 1)
 	eventer.On("test", c)
@@ -64,3 +68,46 @@ func TestOn(t *testing.T) {
 		t.Error("Expected function event with data 'hello world'. Got", data)
 	}
 }
+
+func TestConcurrentUsage(t *testing.T) {
+	rand.Seed(time.Now().Unix())
+	eventer := New()
+	stop := make(chan struct{})
+	recv := make(chan int)
+	poster := func() {
+		for {
+			select {
+			case <-stop:
+				return
+			default:
+				eventer.Post("test", "hi")
+			}
+		}
+	}
+	listener := func(i int) {
+		time.Sleep(time.Duration(rand.Intn(99)) * time.Millisecond)
+		c := eventer.Register("test")
+		// wait for the first event
+		<-c
+		recv <- i
+		// keep receiving to prevent deadlock
+		for {
+			select {
+			case <-stop:
+				return
+			case <-c:
+			}
+		}
+	}
+
+	nlisteners := 200
+	go poster()
+	for i := 0; i < nlisteners; i++ {
+		go listener(i)
+	}
+	// wait until everyone has been served
+	for i := 0; i < nlisteners; i++ {
+		<-recv
+	}
+	close(stop)
+}