[eventsHandler] Use Lock/Unlock to sync a write access

Delete keys from internal maps in a lazy way.
The heavy Lock is acquired only when we have errors.

Signed-off-by: Anton Tiurin <noxiouz@yandex.ru>

api/events.go

@@ -49,11 +49,12 @@ func (eh *eventsHandler) Handle(e *cluster.Event) error {
 		"time", e.Time,
 		"node", cluster.SerializeNode(e.Node))
 
+	var failed []string
+
 	for key, w := range eh.ws {
 		if _, err := fmt.Fprintf(w, str); err != nil {
-			close(eh.cs[key])
-			delete(eh.ws, key)
-			delete(eh.cs, key)
+			// collect them to handle later under Lock
+			failed = append(failed, key)
 			continue
 		}
 
@@ -62,7 +63,24 @@ func (eh *eventsHandler) Handle(e *cluster.Event) error {
 		}
 
 	}
+
 	eh.RUnlock()
+
+	if len(failed) > 0 {
+		eh.Lock()
+
+		for _, key := range failed {
+			if ch, ok := eh.cs[key]; ok {
+				close(ch)
+				// the maps are expected to have the same keys
+				delete(eh.cs, key)
+				delete(eh.ws, key)
+			}
+		}
+
+		eh.Unlock()
+	}
+
 	return nil
 }