Memcache writes returns as soon as the first write succeeds

server/memcache.go

@@ -90,25 +90,32 @@ func (m *memcacheReplicatedClient) writeAll(key string, value []byte, ttl int) e
 		Expiration: int32(ttl),
 	}
 
-	// Write to the memcache servers. At least one write must succeed.
-	caches := m.clients()
-	ch := make(chan error, len(caches))
-	defer close(ch)
-	for _, c := range caches {
+	// Write to all memcache servers. We return as soon as the first
+	// write succeeds, keeping a goroutine around to close the channel
+	// when all the writes are done. This leaks goroutines in case of
+	// network issues, so keep a short timeout.
+	ch := make(chan error, 1)
+	var wg sync.WaitGroup
+
+	for _, c := range m.clients() {
+		wg.Add(1)
 		go func(c *memcache.Client) {
 			ch <- c.Set(item)
+			wg.Done()
 		}(c)
 	}
-	var ok bool
-	for i := 0; i < len(caches); i++ {
-		if err := <-ch; err == nil {
-			ok = true
+
+	go func() {
+		wg.Wait()
+		close(ch)
+	}()
+
+	for err := range ch {
+		if err == nil {
+			return nil
 		}
 	}
-	if !ok {
-		return errors.New("all memcache servers failed")
-	}
-	return nil
+	return errors.New("all memcache servers failed")
 }
 
 func (m *memcacheReplicatedClient) readAny(key string) ([]byte, bool) {
@@ -125,14 +132,13 @@ func (m *memcacheReplicatedClient) readAny(key string) ([]byte, bool) {
 	for _, c := range m.clients() {
 		wg.Add(1)
 		go func(c *memcache.Client) {
-			defer wg.Done()
-
 			if item, err := c.Get(key); err == nil {
 				select {
 				case ch <- item.Value:
 				default:
 				}
 			}
+			wg.Done()
 		}(c)
 	}