Apache ActiveMQ Out Of Memory!

Apache ActiveMQ is adaptable and configurable. A large part of its popularity is due to its flexibility. However, it comes with a default activemq.xml configuration file that cannot possibly suit everybody's needs. The default configuration is a compromise between memory utilisation, low latency and high throughput, with a smattering of feature demonstrations. In all, it is probably too much for one configuration file, but that is another issue that is in part addressed in version 5.3.0.

With the current defaults, it is relatively easy to push the broker's heap memory utilization past the -Xmx512m heap limit passed to the JVM in the start script. When that happens the broker begins to fail in various places with java.lang.OutOfMemoryError: unable to create new native thread or java.lang.OutOfMemoryError: Java heap space.

What to do?
Well Google is your friend but there is also the ActiveMQ FAQ and particularly the entry that deals with the likely causes and relevant configuration that can alleviate ActiveMQ OutOfMemoryError Exceptions.

In short, the answer is nearly always configuration and the intent is that the OutOfMemory FAQ entry will provide a comprehensive reference for the relevant options. Let it be your first port of call.