While I haven't run artemis in kubernetes or another container, I have seen a similar phenomenon in certain situations. What can you tell us about the average size of your messages, and can you post details about your queue/topic configuration. On occasion when I have artemis processing either a large number (millions) or messages, or some few hundred very large messages and also made changes to the memory configuration and/or global-max-size, I've seen artemis run away with the CPU in one thread and begin responding very poorly. It seems to be especially acute if you start an artemis instance with an unbounded global-max-size and less memory than the size of your in-flight messages in the journal. My experience is all on windows VMs, using the journaling file system so may not be relevant, but the situation you're describing did ring a bell. Please post those config details and I'd be glad to review them.
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