Persistent vs. in-memory queues

Question

Hello Experts,
we are developing an SMS-based app. As of now, we imagine it like this:
- Receiver thread reads incoming SMS messages and puts them into a queue
- Processor thread reads messages from the queue and executes logic on them
- Logger thread reads the same messages as Processor and logs them into a database.
We decided to go for in-memory JMS solution because of performance. My questions are
(1) since we are worried that database operations might not put up with message throughputs during peak periods, we create that Logger thread. My understanding here is, if there are to many SMS to get logged into the DB, they will still be processed by the Processor, but logged with some delay. Is that correct? Or should we use persistent JMS? In such case, wouldn't it slow down the app?
(2) having those 2 consumers, should we go for queues or topics? All threads will run on the same machine.
Any help is much appreciated!
Thanks, regards,
Pawel

Answer 1

Hi,
I think that nimo's solution is the one to go for. However, if you cannot afford to loose a SMS message that is added in the processor queue then, you must use persistent messages. Now, if you are using an additional �logger� queue, I guess that you cannot afford a processed message not being logged. Hence, your processor thread should consume a SMS message and send a logging message within the same transaction. Moreover, logging messages must be persistent (even if your SMS messages are not persistent). That should work well apart from the fact that you may want to consume your logging message and update your database within the same transaction. If you don�t do that and have troubles when updating your DB, a message is removed from the logging queue and the DB is not updated leaving your system in an inconsistent state. To perform DB updates and message consumption within the same transaction you must use a JMS provider that offers XA support. A MDB will handle XA transaction for you. However, if you don�t want to use a heavy weight app server you can go for Arjuna MDS that provides XA support as well.
Hope this helps
Arnaud
www.arjuna.com