messaging: able to pub sub multiple partitions

weed/messaging/client/subscriber.go

@@ -9,10 +9,33 @@ import (
 )
 
 type Subscriber struct {
-	subscriberClient messaging_pb.SeaweedMessaging_SubscribeClient
+	subscriberClients []messaging_pb.SeaweedMessaging_SubscribeClient
+	subscriberId      string
 }
 
 func (mc *MessagingClient) NewSubscriber(subscriberId, namespace, topic string) (*Subscriber, error) {
+	// read topic configuration
+	topicConfiguration := &messaging_pb.TopicConfiguration{
+		PartitionCount: 4,
+	}
+	subscriberClients := make([]messaging_pb.SeaweedMessaging_SubscribeClient, topicConfiguration.PartitionCount)
+
+	for i := 0; i < int(topicConfiguration.PartitionCount); i++ {
+		client, err := mc.setupSubscriberClient(subscriberId, namespace, topic, int32(i))
+		if err != nil {
+			return nil, err
+		}
+		subscriberClients[i] = client
+	}
+
+	return &Subscriber{
+		subscriberClients: subscriberClients,
+		subscriberId:      subscriberId,
+	}, nil
+}
+
+func (mc *MessagingClient) setupSubscriberClient(subscriberId, namespace, topic string, partition int32) (messaging_pb.SeaweedMessaging_SubscribeClient, error) {
+
 	stream, err := messaging_pb.NewSeaweedMessagingClient(mc.grpcConnection).Subscribe(context.Background())
 	if err != nil {
 		return nil, err
@@ -23,7 +46,7 @@ func (mc *MessagingClient) NewSubscriber(subscriberId, namespace, topic string)
 		Init: &messaging_pb.SubscriberMessage_InitMessage{
 			Namespace:     namespace,
 			Topic:         topic,
-			Partition:     0,
+			Partition:     partition,
 			StartPosition: messaging_pb.SubscriberMessage_InitMessage_TIMESTAMP,
 			TimestampNs:   time.Now().UnixNano(),
 			SubscriberId:  subscriberId,
@@ -42,20 +65,27 @@ func (mc *MessagingClient) NewSubscriber(subscriberId, namespace, topic string)
 		// TODO follow redirection
 	}
 
-	return &Subscriber{
-		subscriberClient: stream,
-	}, nil
+	return stream, nil
+
 }
 
-func (s *Subscriber) Subscribe(processFn func(m *messaging_pb.Message)) error {
+func (s *Subscriber) doSubscribe(partition int, processFn func(m *messaging_pb.Message)) error {
 	for {
-		resp, listenErr := s.subscriberClient.Recv()
+		resp, listenErr := s.subscriberClients[partition].Recv()
 		if listenErr == io.EOF {
 			return nil
 		}
 		if listenErr != nil {
+			println(listenErr.Error())
 			return listenErr
 		}
 		processFn(resp.Data)
 	}
 }
+
+// Subscribe starts goroutines to process the messages
+func (s *Subscriber) Subscribe(processFn func(m *messaging_pb.Message)) {
+	for i:=0;i<len(s.subscriberClients);i++{
+		go s.doSubscribe(i, processFn)
+	}
+}