In TIBCO EMS (or other JMS), how do I create a scalable request/response processor?

Question

I'm working on a server side project providing a request/response service over TIBCO EMS and am looking for advice on best practice to archive scalability as well as low latency in this service. I'm doing this on .NET, but as TIBCO EMS is supposedly implementing the JMS specification, I assume that advice for other JMS implementations as well as platforms (Java) would be relevant.

Currently, we are using one Connection, one Session, one Consumer and listening to messages using a callback on that single Consumer. Each request is processed on the callback thread synchronously replies on a different Queue (but same Session). This works, but does not appear to scale - the CPU load is negligible even at high transaction rates, but the latency for request keeps growing.

I assume what is happening is that EMS uses a single thread for the callback, and the processing time as well as the time required to send the reply therefore blocks other requests from being processed, but - what is the best way of getting this to scale?

One way would be to immediately schedule the actual processing of an incoming request on the thread pool once received. This is a quick fix and would scale, but would introduce additional latency and would introduce threading concerns around use of the session. Another one would be to have a number of Session objects, or even Connection objects? Can anyone please advice on best practice for doing this, I imagine it must be one of the more common usage patterns out there...

Answer 1

You need a two-step queuing process. Your callback should do as little as possible and my preferred option is for it merely to Enqueue the message onto a local Queue<T>. This Queue can then be accessed by multiple local threads, Dequeuing and processing any available items and allowing the JMS queueing process to proceed, eliminating a large amount of latency.

You'll need to do a bit of synchronisation to get your results returned to the right consumer but that should be relatively trivial.

Answer 2

The processing of messages is influenced by the Acknowledgment mode and the count of parallel sessions.

From what you tell, it sounds to me you only use one session and acknowledge (client acknowledgement) the message after processing (and replying) one after another.

This could be speed up by using auto acknowledgment (acknowledge the message while receiving) and/or using multiple sessions in parallel.

On top, EMS can speed up message pushing by a parameter called "prefetch count" which reduces the time to fetch new messages from the Queue. (see the EMS documentation).

Late answer, but i hope it helps ;)