ActiveMQ - memory not released after consuming all messages

Question

I've made a test, based on the example solution of the activemq-cpp library. In the test I send 50,000 messages to a queue, and after they're all sent I consume them, with INDIVIDUAL_ACKNOWLEDGE on the session and message->acknowledge() on every consumed message. The consumer is asynchronous.

Memory (private working set) of java.exe before sending messages: 209,320 KB. After sending all messages: 412,548 KB. After consuming all messages: 434,637 KB. Meaning, although queue size is 0, memory was not released. What am I missing? Thanks.

Answer 1

Besides the JVM processing mentioned above there are a number of other factors that are in play here. Depending on the state of the broker when you started the producer sending messages there could be a number of resources that where allocated on the broker to create the Queue and various other management objects which will then remain in memory to facilitate message routing etc. To truly analyze the memory usage and check for leaks you should use a tool like Yourkit etc.