Do not allow writing events after fluent.Close()

fluent/fluent.go

@@ -98,7 +98,7 @@ type Fluent struct {
 	cancelDialings context.CancelFunc
 	pending        chan *msgToSend
 	pendingMutex   sync.RWMutex
-	chanClosed     bool
+	closed         bool
 	wg             sync.WaitGroup
 
 	muconn sync.RWMutex
@@ -274,7 +274,11 @@ func (f *Fluent) postRawData(msg *msgToSend) error {
 	if f.Config.Async {
 		return f.appendBuffer(msg)
 	}
+
 	// Synchronous write
+	if f.closed {
+		return fmt.Errorf("fluent#postRawData: Logger already closed")
+	}
 	return f.writeWithRetry(context.Background(), msg)
 }
 
@@ -350,11 +354,11 @@ func (f *Fluent) EncodeData(tag string, tm time.Time, message interface{}) (msg
 func (f *Fluent) Close() (err error) {
 	if f.Config.Async {
 		f.pendingMutex.Lock()
-		if f.chanClosed {
+		if f.closed {
 			f.pendingMutex.Unlock()
 			return nil
 		}
-		f.chanClosed = true
+		f.closed = true
 		f.pendingMutex.Unlock()
 
 		if f.Config.ForceStopAsyncSend {
@@ -364,7 +368,7 @@ func (f *Fluent) Close() (err error) {
 
 		close(f.pending)
 		// If ForceStopAsyncSend is false, all logs in the channel have to be sent
-		// before closing the connection. At this point chanClosed is true so no more
+		// before closing the connection. At this point closed is true so no more
 		// logs are written to the channel and f.pending has been closed, so run()
 		// goroutine will exit as soon as all logs in the channel are sent.
 		if !f.Config.ForceStopAsyncSend {
@@ -374,6 +378,7 @@ func (f *Fluent) Close() (err error) {
 
 	f.muconn.Lock()
 	f.close()
+	f.closed = true
 	f.muconn.Unlock()
 
 	// If ForceStopAsyncSend is true, we shall close the connection before waiting for
@@ -383,15 +388,14 @@ func (f *Fluent) Close() (err error) {
 	if f.Config.ForceStopAsyncSend {
 		f.wg.Wait()
 	}
-
 	return
 }
 
 // appendBuffer appends data to buffer with lock.
 func (f *Fluent) appendBuffer(msg *msgToSend) error {
 	f.pendingMutex.RLock()
 	defer f.pendingMutex.RUnlock()
-	if f.chanClosed {
+	if f.closed {
 		return fmt.Errorf("fluent#appendBuffer: Logger already closed")
 	}
 	select {

fluent/fluent_test.go

@@ -732,6 +732,39 @@ func TestCloseWhileWaitingForAckResponse(t *testing.T) {
 	}, "failed to close the logger")
 }
 
+func TestSyncWriteAfterCloseFails(t *testing.T) {
+	d := newTestDialer()
+
+	go func() {
+		f, err := newWithDialer(Config{Async: false}, d)
+		if err != nil {
+			t.Errorf("Unexpected error: %v", err)
+		}
+
+		err = f.PostWithTime("tag_name", time.Unix(1482493046, 0), map[string]string{"foo": "bar"})
+		if err != nil {
+			t.Errorf("Unexpected error: %v", err)
+		}
+
+		err = f.Close()
+		if err != nil {
+			t.Errorf("Unexpected error: %v", err)
+		}
+
+		// Now let's post some event after Fluent.Close().
+		err = f.PostWithTime("tag_name", time.Unix(1482493050, 0), map[string]string{"foo": "buzz"})
+
+		// The event submission must fail,
+		assert.NotEqual(t, err, nil);
+
+		// and also must keep Fluentd closed.
+		assert.NotEqual(t, f.closed, false);
+	}()
+
+	conn := d.waitForNextDialing(true, false)
+	conn.waitForNextWrite(true, "")
+}
+
 func Benchmark_PostWithShortMessage(b *testing.B) {
 	b.StopTimer()
 	d := newTestDialer()