I have a Java application, which uses an Oracle Queue to store messages in the queue for later processing by multiple threads consuming queued messages. The messages in this queue can be related to each other, and must therefore be processed in a specific order based on the business logic of my application. Basically, I want to achieve that the dequeueing of one message A is held back as long as another message B in the queue has not been completely processed. The only weapon given by Oracle AQ I see here, are the Delay and an Priority parameters. These, however, cannot be used to achieve the scenario outlined above, since there are situations, where two related messages still can be dequeued and processed at the same time. Are there any tools that can help establishing an advanced processing order of messages?
I came to the conclusion that it is not a good idea to order these messages using the queue, because it would need a custom and very specialized dequeue strategy, which has a very bad smell to me, both, complexity and most likely performance wise. It also tries to fix communication protocol issues using the queue, which are application specific and therefore should find treatment in the application itself. Instead, the application / communication protocol should be tolerant enough to handle ordering issues.