MQSeries.net :: View topic - MQGET with wait and threading in Java (non-JMS)

gorilla · Posted: Wed Dec 07, 2005 4:12 am Post subject:

A while ago I wrote a program using the non-JMS Java interface. It was designed to read out a queue which was been loaded by a fast program (designed to demonstrate how fast you can do MQPUTs from Java) so the GET program was (a) reading a lot of messages and (b) reporting its times.

I originally wrote it with two separete GET threads - one for the data queue and the other for commands carried as MQ messages (a side effect of the "cut and paste" school of prgramming

Anyway, I had two Java threads, each one doing a get wait, but on different queues. Get wait is a blocking call, so both threads are on timed loops so they can react to external signals.

This produced an unexpected effect: the two threads interfered with each other. As far as I could make out they were running in series instead of in parallel. The command thread would wait out one cycle, during which the data thread did nothing, then the data thread would read messages for one cycle, then the command thread would wait one cycle again. Effective get rate was a few hundred messages per second.

This isn't much of a problem (it cost maybe 10 lines of code in total to bypass) but I'd like to understand better where it's coming from.

I got around it by removing the get wait - that is, the code does a get, reacts to the "no message in queue" exception, and uses Thread.sleep before checking again.
FWIW, the current version runs about as fast as an unthreaded version with just one get wait - I got over 10K messages per second on a laptop PC (small non-persistent messages of course) and something over 2000 per second with persistent messages.

Does anyone know what the "interference effect" is due to?