Hi Hans
We have implemented a connection between MQ Series 5-7 and axis2 using
the axis2 1.4 JMS connectivity and a point-to-point set-up. The
implementation basically works, but some questions remain.
As long as we use a request/response pattern in the client connecting
to our service via jms all is well. In this scenario, the client
generates requests at a rate not higher than it receives results.
But if we split the client in a separate request Sender and Response
reader the following happens:
1) The request sender sends a fixed number (e.g. 10000) messages to
the MQ Series request queue.
2) Axis2 immediately starts eating messages out of the queue. Since
the JMS worker is single threaded by nature it can handle at most 1
request at a time. The JMS listener starts queueing messages read from
MQ Series at the maximum rate it can. This it can do faster than the
single JMS worker can handle the requests.
3) As a result, the queue inside axis2 grows until all available
memory is exhausted and then it crashes with an Out Of Memory
exception. All messages that were loaded in the axis2 queue but not
processed by the service are lost.
Would it not be better if the JMS Listener would not keep a (long)
queue of messages, but block instead until the previous request was
finished? That would keep the memory consumption of Tomcat constant
and avoids loosing messages. Maybe things are different in a
Publish/Subscribe scenario.
Yes, your suggestion is good..
Also, in a post on axis2-dev, Asanka Perera says jms transport in
axis2 is deprecated. Is this true? Are there any recommendations
regarding the use of jms transport in combination with axis2?
The reason for this confusion is since we developed the JMS transport
(and a few other transports such as File, non-blocking http/s, mail,
etc) on the Apache Synapse project and checked in this code into the
Axis2 SVN creating a copy.. which was not properly maintained. The
Synapse version evolved and enhanced, while the Axis2 code basically was
not properly maintained. We also have plans under Apache Synapse to
support JTA and the new SOAP/JMS spec and many other enhancements as
well.. and to consolidate the two versions into one common transport
developed outside both of those projects. This however, is a few months
away..
asankha
--
Asankha C. Perera
WSO2 - http://wso2.org
http://esbmagic.blogspot.com
