How can sender know the message already be consumed with MQ JMS API?
I'm dealing with a standalone MQ JMS application, our app need to "aware" that client already consumed the message producer put on the queue. Because client app is not responsible by us. So we cannot let them to write something like "msg.acknowledge();" thing on their side (msg.acknowledge() is not the right approach on my condition.). I search the history answer in the stackoverflow. Find following is quite the same what I want:
https://stackoverflow.com/questions/6521117/how-to-guarantee-delivery-of-the-message-in-jms
Do the JMS spec or the various implementations support delivery confirmation of messages?
My question is, is there any other way to archive this in the MQ API or JMS API? I need to do the coding only on the msg produce side, it is can be queue or topic.
Another question is in the JMS the acknowledge mode CLIENT_ACKNOWLEDGE, is that produce irrelevant? I always believe that this mode can block the application when call send() method until the client consume the message and call the msg.acknowledge(), but seems not like that. The produce just exit the app after message be delivered, and the message just store in the queue until client call the acknowledge(). Is that possible let the producer app hang there wait until the message be acknowledged by the client?
If my concept is not right, just correct me, thanks.
Answer
The main intention of message queuing is to decouple producer and consumer. Producer does not need to wait for the message to be consumed by the consumer, it can continue it's job. Ideally if producer needs to know if the message has been processed by consumer or not, it should wait for consumer to send a response message on another queue.
Message acknowledgement has nothing to do with producer. Message acknowledgement is the way a consumer tells the messaging provider to remove the message from a queue after the message has been delivered to an application.
There is auto acknowledge where the JMS providers (like MQ JMS), after delivering message to an application, tell the messaging provider to remove the message from queue. Then there is client acknowledge where, after receiving a message, the application explicitly tells the messaging provider to remove message from a queue.
Is there is a reason why the producer has to wait for consumer to receive the message? One way, though not elegant, could be: Once the message is sent, use the message id of the sent message and try to browse for that message. If message is not found, you can assume it has been consumed