消费来自JMS主题的消息时出现延迟

Question

I have a topic with durable subscribers. I can publish and consume the messages, however I see there is some delay while reading the messages from topic.

I am not able read the messages in a single call. I need to call the method multiple times to read the messages. Am I missing anything?

    private void publishMessage() {
        TopicConnection topicConnection = null;
        TopicSession topicSession = null;
        TopicPublisher topicPublisher = null;
        try {
          topicConnection = connectionFactory.createTopicConnection();
          topicSession = topicConnection.createTopicSession(false, TopicSession.AUTO_ACKNOWLEDGE);
          Topic topicName= topicSession.createTopic(topicName);
          topicPublisher = topicSession.createPublisher(topicName);
          ObjectMessage message = topicSession.createObjectMessage(customObject)
          message.setStringProperty("user", userProperty);
          topicPublisher.publish(message, DeliveryMode.PERSISTENT, Message.DEFAULT_PRIORITY, timeToLive);
        } catch (JMSException e) {
          throw new RuntimeException("Error Sending UMessage", e);
        } finally {
          closeConnections(null, topicPublisher, topicSession, topicConnection);
        }
    }

public void consumeMessages(String userId, int maxResults) {
    TopicConnection topicConnection = null;
    TopicSession topicSession = null;
    TopicSubscriber topicSubscriber = null;

    try {
      topicConnection = connectionFactory.createTopicConnection("guest","guest");
      topicConnection.setClientID("topic");
      topicSession = topicConnection.createTopicSession(false, TopicSession.AUTO_ACKNOWLEDGE);
      Topic topicName= topicSession.createTopic(topicName);
      topicSubscriber = topicSession.createDurableSubscriber(topicName, "subscriptionname", String.format("user = '%s'", userName), false);
      topicConnection.start();
      Message msg = null;

      do {
        msg = topicSubscriber.receiveNoWait();
        if (msg instanceof ObjectMessage) {
          ObjectMessage om = (ObjectMessage) msg;
         else {
            log.error(String.format(" %s", om.getObject().getClass().getSimpleName()));
          }
        } else if (msg != null) {
          log.error(String.format("e %s", msg.getClass().getSimpleName()));
        }
      } while (msg != null && out.size() <= maxResults);
    } catch (JMSException e) {
      throw new RuntimeException("Error retrieving User Messages", e);
    } finally {
      closeConnections(topicSubscriber, null, topicSession, topicConnection);
    }
    return out;
}

Answer 1

You are calling receiveNoWait() which will retrieve one message at a time. What normally happens, depending on your JMS provider, is that the JMS client will retrieve a number of messages at once and cache them on the client side to reduce network latency. When you call receive it is then taking the message from this cache and giving it to you.

If you are seeing minute long delays there is either something wrong with how you are putting these messages onto the topic or you are blocking your message receive while you process each message. If you would like to not block your message receipt while processing take a look at implementing the MessageListener interface instead of the using the receive methods or you can take the messages from your receive method and process them on a thread pool asynchronously.

When you create the consumer you can add the listener like so:

MessageListener listener = new MyListener();
consumer.setMessageListener(listener);

Then create a class to handle the messages or implement the interface in your existing consumer class:

public class MyListener implements MessageListener {
  public void onMessage(Message message)
  {
     TextMessage text = (TextMessage) message;

     System.out.println("Message: " + text.getText());
  }
}