fix: goroutine leak in publisher on close

internal/connectionmanager/connection_manager.go

@@ -23,6 +23,13 @@ type ConnectionManager struct {
 	reconnectionCount   uint
 	reconnectionCountMu *sync.Mutex
 	dispatcher          *dispatcher.Dispatcher
+
+	// universalNotifyBlockingReceiver receives block signal from underlying
+	// connection which are broadcasted to all publisherNotifyBlockingReceivers
+	universalNotifyBlockingReceiver     chan amqp.Blocking
+	universalNotifyBlockingReceiverUsed bool
+	publisherNotifyBlockingReceiversMu  *sync.RWMutex
+	publisherNotifyBlockingReceivers    []chan amqp.Blocking
 }
 
 type Resolver interface {
@@ -62,17 +69,20 @@ func NewConnectionManager(resolver Resolver, conf amqp.Config, log logger.Logger
 	}
 
 	connManager := ConnectionManager{
-		logger:              log,
-		resolver:            resolver,
-		connection:          conn,
-		amqpConfig:          conf,
-		connectionMu:        &sync.RWMutex{},
-		ReconnectInterval:   reconnectInterval,
-		reconnectionCount:   0,
-		reconnectionCountMu: &sync.Mutex{},
-		dispatcher:          dispatcher.NewDispatcher(),
+		logger:                             log,
+		resolver:                           resolver,
+		connection:                         conn,
+		amqpConfig:                         conf,
+		connectionMu:                       &sync.RWMutex{},
+		ReconnectInterval:                  reconnectInterval,
+		reconnectionCount:                  0,
+		reconnectionCountMu:                &sync.Mutex{},
+		dispatcher:                         dispatcher.NewDispatcher(),
+		universalNotifyBlockingReceiver:    make(chan amqp.Blocking),
+		publisherNotifyBlockingReceiversMu: &sync.RWMutex{},
 	}
 	go connManager.startNotifyClose()
+	go connManager.readUniversalBlockReceiver()
 	return &connManager, nil
 }
 

internal/connectionmanager/safe_wraps.go

@@ -8,10 +8,43 @@ import (
 func (connManager *ConnectionManager) NotifyBlockedSafe(
 	receiver chan amqp.Blocking,
 ) chan amqp.Blocking {
-	connManager.connectionMu.RLock()
-	defer connManager.connectionMu.RUnlock()
+	connManager.connectionMu.Lock()
+	defer connManager.connectionMu.Unlock()
 
-	return connManager.connection.NotifyBlocked(
-		receiver,
-	)
+	// add receiver to connection manager.
+	connManager.publisherNotifyBlockingReceiversMu.Lock()
+	connManager.publisherNotifyBlockingReceivers = append(connManager.publisherNotifyBlockingReceivers, receiver)
+	connManager.publisherNotifyBlockingReceiversMu.Unlock()
+
+	if !connManager.universalNotifyBlockingReceiverUsed {
+		connManager.connection.NotifyBlocked(
+			connManager.universalNotifyBlockingReceiver,
+		)
+		connManager.universalNotifyBlockingReceiverUsed = true
+	}
+
+	return receiver
+}
+
+// readUniversalBlockReceiver reads on universal blocking receiver and broadcasts event to all blocking receivers of
+// connection manager.
+func (connManager *ConnectionManager) readUniversalBlockReceiver() {
+	for b := range connManager.universalNotifyBlockingReceiver {
+		connManager.publisherNotifyBlockingReceiversMu.RLock()
+		for _, br := range connManager.publisherNotifyBlockingReceivers {
+			br <- b
+		}
+		connManager.publisherNotifyBlockingReceiversMu.RUnlock()
+	}
+}
+
+func (connManager *ConnectionManager) RemovePublisherBlockingReceiver(receiver chan amqp.Blocking) {
+	connManager.publisherNotifyBlockingReceiversMu.Lock()
+	for i, br := range connManager.publisherNotifyBlockingReceivers {
+		if br == receiver {
+			connManager.publisherNotifyBlockingReceivers = append(connManager.publisherNotifyBlockingReceivers[:i], connManager.publisherNotifyBlockingReceivers[i+1:]...)
+		}
+	}
+	connManager.publisherNotifyBlockingReceiversMu.Unlock()
+	close(receiver)
 }

publish.go

@@ -58,6 +58,8 @@ type Publisher struct {
 	notifyPublishHandler func(p Confirmation)
 
 	options PublisherOptions
+
+	blockings chan amqp.Blocking
 }
 
 type PublisherConfirmation []*amqp.DeferredConfirmation
@@ -286,6 +288,7 @@ func (publisher *Publisher) Close() {
 		publisher.options.Logger.Warnf("error while closing the channel: %v", err)
 	}
 	publisher.options.Logger.Infof("closing publisher...")
+	publisher.connManager.RemovePublisherBlockingReceiver(publisher.blockings)
 	go func() {
 		publisher.closeConnectionToManagerCh <- struct{}{}
 	}()

publish_flow_block.go

@@ -26,6 +26,7 @@ func (publisher *Publisher) startNotifyFlowHandler() {
 func (publisher *Publisher) startNotifyBlockedHandler() {
 	blockings := publisher.connManager.NotifyBlockedSafe(make(chan amqp.Blocking))
 	publisher.disablePublishDueToBlockedMu.Lock()
+	publisher.blockings = blockings
 	publisher.disablePublishDueToBlocked = false
 	publisher.disablePublishDueToBlockedMu.Unlock()