Hi! After some heavy digging about Producer Flow control and the systemUsage properties a couple of years ago, I thought I quite understood it. But yesterday I found that one of my configs was not behaving exactly as I expected, so started doing some tests, and I see certain behaviours which don't seem to match what the docs and posts that I find on the list or other forums say.
"storeUsage" is perfectly clear, it's the max space that persistent messages can use to be stored in disk. "tempUsage"" applies to file cursors on non-persistent messages, so as to flush to disk if memory limits are reached (I don't care much about this one anyway, I always use persistent messages). Now, according to most posts, memoryUsage would be the maximum memory that the broker would be available to use. On this post: http://stackoverflow.com/questions/7646057/activemq-destinationpolicy-and-systemusage-configurationit says that "memoryUsage corresponds to the amount of memory that's assigned to the in-memory store". For example, on my tests using the following config (only showing relevant parts): <policyEntry queue=">" producerFlowControl="false" optimizedDispatch="true"> <deadLetterStrategy> <individualDeadLetterStrategy queuePrefix="DLQ." useQueueForQueueMessages="true" /> </deadLetterStrategy> </policyEntry> <systemUsage> <systemUsage> <memoryUsage> <memoryUsage limit="100 mb"/> </memoryUsage> <storeUsage> <storeUsage limit="1 gb" name="foo"/> </storeUsage> <tempUsage> <tempUsage limit="3 gb"/> </tempUsage> </systemUsage> </systemUsage> With that config I would expect the broker to use 100 mb of maximum memory among all queues. So it could maybe use 30mb in one queue and 70mb in second queue. 1) What I'm seeing is that if I start feeding a queue without consuming it, the "Memory percent used" grows up to 70%, after that it doesn't grow anymore. What is it doing exactly there? The first 70% is stored in memory (apart from disk since it's persistent), and all the rest that continues being fed goes just to disk? 2) If then I start feeding a 2nd queue, "Memory percent used" continues growing until it reaches 140%. So it looks like memoryUsage does not apply globally, but on a per queue basis? Using memoryLimit on the queue's policyEntry gives more control over this, but it's just a variation, "Memory percent used" can grow more than 100% anyway. 3) If #2 is true, then how would I prevent the broker from running out of memory in case queues would continue to be created? Maybe I'm misunderstanding and some of these settings make no sense when producerFlowControl is disabled? Thanks in advance. Juan
