Hi, Sorry, this is a bit of a long post/question... I have an application where I need to use the synchronous API of the activemq-cpp library where I will have one thread that needs to subscribe to, and receive messages from, multiple topics. After studying the API docs, I don't see a way to efficiently wait for messages from multiple MessageConsumer instances (belonging to the same Session) and receive the messages in the order they were published. (I'm not sure that ActiveMQ guarantees message order across multiple topics.) The only approach I see would be to poll the consumers using receiveNoWait(); however, that will burn CPU cycles and won't preserve message order across topics.
I experimented with adapting the Asynchronous API to my needs; however, I can't use the MessageListener approach due to the need to perform potentially long/complex processing within the onMessage callback function - and deferring the processing till later leads to complexity with Message/Request buffering within the client code under heavy message loads (i.e. I can't implement flow control within client code without eventual deadlocks). This lead me to the MessageAvailableListener API, which seemed like a good solution. I used an internal buffer to store pointers to MessageConsumer instances with available messages (messages stay in the prefetch buffer, so flow control works), then synchronize with an efficiently waiting receiver to receive the messages. This almost worked; however, it appears that the receiver does not always receive onMessageAvailable() callbacks for every message delivered to the prefetch buffer, which causes the client code to get out of synch with the incoming message flow. I'm not sure if this is a bug or not, as the issue arises when dynamically subscribing to topics under heavy load. I stop() the Connection, create the consumer, set the listener, then start() the Connection, but messages still seem to arrive in the prefetch buffer. (The test case for this is fairly complex...) So, does anyone have any suggestions for an approach to have a single client thread synchronously and efficiently receive messages from multiple message consumers? (i.e. like the socket API and using the select() statement) Thanks in advance! -- View this message in context: http://activemq.2283324.n4.nabble.com/Activemq-cpp-Synchronous-Receive-from-Multiple-Consumers-tp4702375.html Sent from the ActiveMQ - User mailing list archive at Nabble.com.
