ActiveMQ prefetch and Spring DMLC advice from Torsten

A piece of advice on ActiveMQ prefetch and Spring DMLC from my colleague Torsten.


I just remembered a lesson learned about prefetch and Spring DMLC:
If you configure DMLC to use CACHE_SESSION or below (i.e. CACHE_CONNECTION or CACHE_NONE) *and* when you don't use a CachingConnectionFactory (e.g SingleConnectionFactory), then you should set the prefetch for the Spring consumer to only 1 or 0.
That is because when not caching the consumer, a new JMS consumer is recreated for every msg that Spring will ask the broker for.
And if there are many msgs on the queue, the broker will prefetch e.g. 1000 msgs to the consumer although the consumer will only process one msg.
Spring DMLC then recycles the JMS consumer with 999 unprocessed msgs. This obviously causes to much and unnecessary load on the network.

So possible solutions in this case:
1) prefetch=0 or 1,
2) configure DMLC to use CACHE_CONSUMER, or
3) use Springs CachingConnectionFactory

Quick and short post on jmxrmi exception in FUSE HQ.

If you even see following exception when using FUSE HQ or Hyperic HQ it is most likely an issue with what JDK/JRE you (or rather HQ) is using. The problem occurred while collecting statistics from FUSE ESB (Servicemix) and FUSE Message Broker (ActiveMQ).

Here is the exception:

org.hyperic.hq.product.PluginException: javax.naming.NameNotFoundException: jmxrmi
 at org.hyperic.hq.product.jmx.MxServerDetector.discoverServices(MxServerDetector.java:404)
 at org.hyperic.hq.product.ServerDetector.discoverResources(ServerDetector.java:203)
 at org.hyperic.hq.autoinventory.agent.server.RuntimeAutodiscoverer.doRuntimeScan_internal(RuntimeAutodiscoverer.java:272)
 at org.hyperic.hq.autoinventory.agent.server.RuntimeAutodiscoverer.doRuntimeScan(RuntimeAutodiscoverer.java:205)
 at org.hyperic.hq.autoinventory.ScanManager.mainRunLoop(ScanManager.java:165)
 at org.hyperic.hq.autoinventory.ScanManager.access$000(ScanManager.java:41)
 at org.hyperic.hq.autoinventory.ScanManager$1.run(ScanManager.java:107)
Caused by: java.io.IOException: javax.naming.NameNotFoundException: jmxrmi
 at mx4j.remote.resolver.rmi.Resolver.lookupStubInJNDI(Resolver.java:100)
 at mx4j.remote.resolver.rmi.Resolver.lookupRMIServerStub(Resolver.java:72)
 at mx4j.remote.resolver.rmi.Resolver.lookupClient(Resolver.java:52)
 at javax.management.remote.rmi.RMIConnector.connect(RMIConnector.java:119)
 at javax.management.remote.JMXConnectorFactory.connect(JMXConnectorFactory.java:38)
 at org.hyperic.hq.product.jmx.MxUtil.getMBeanConnector(MxUtil.java:445)
 at org.hyperic.hq.product.jmx.MxServerDetector.discoverServices(MxServerDetector.java:401)

The cause in my case:
FUSE HQ agent was using JRE 1.4 bundled with it which was causing the problem.
Why : There are some incompatibilities in JMX stuff when it comes to using the same code with JDK 1.4 and JDK 1.5 and apparently moving to JDK/JRE 1.5 got rid of this problem.
I don't know much about JMX so don't know what all incompatibilities are between tow of them. Anyone who reads (in first place) and knows the differences and could comment on this post it would help everyone.