Imagine a sequential JMS invocation across Camel routes, such as the following:
The camel-jms consumer listening on test1 will set the JMSCorrelationID header to the JMSMessageID for that exchange.
When the response returns to the route and sent to test2, this consumer also uses the same JMSCorrelationID as before.
IMHO, this behaviour is incorrect from the pragmatic perspective. Why should test2 reuse the Message ID from test1 after all?
Despite that, the correlation works for simple cases, but for complex routing with parallel JMS exchanges, it doesn't because the correlation ID is not unique for each exchange. Consider the following splitter:
There are several solutions here:
- Remove the JMSCorrelationID header before each request to test2
- Enable the useMessageIDAsCorrelationID option on both producer and consumer endpoints
- Create a new option to assign a unique ID to the JMSCorrelationID header
The downside of 2 is that the message ID is only assigned after the JMS dispatch, so the component updates the correlation map with the final JMSMessageID after the JMS dispatch. Also, camel-jms is also prepared to handle cases where the reply comes in before the map update has occurred, by waiting 5 seconds if an unknown correlation ID is received, blocking the receipt of any further replies. You will agree with me this is inefficient and flaky for enterprise deployments.
That's where the upside of 3 lies. By expressly setting a static unique ID as the correlation ID, we get rid of these race conditions and inefficiencies.
I propose calling this option 'assignUniqueCorrelationID'.
I'm happy to submit a patch for this, targeting 2.10.1.