[FIXED] Health check must not recreate stream/consumer #6362
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Signed-off-by: Maurice van Veen <github@mauricevanveen.com>
Signed-off-by: Maurice van Veen <github@mauricevanveen.com>
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Calling healthz could result in streams and/or consumers to be restarted.
There's a race condition that can happen where a user recreates a stream/consumer and the health check kicks in at that moment. This would result in reviving a just-deleted stream/consumer, resulting in either dead streams/consumers remaining or potentially leaderless states if different RAFT groups would remain.
A stream/consumer must not be restarted in the health check as it has no awareness of what's happening in another part of the system. Is the stream just deleted, is it restarting due to an error, is it actually stopped due to a bug? It can't know, and it shouldn't assume it's safe to restart. Due to the way the JS lock is used combined with creating copies of the stream/consumer assignment means that various race conditions can happen where restarting would be the wrong choice.
More importantly (and put simply), stream/consumer assignments MUST only be changed via meta entries or meta snapshots. Doing it in any other place can result in race conditions/ordering issues. (Just like snapshotting in any other place than in the monitor routine resulted in race conditions before: #6153)
Detecting and correcting RAFT node skew is kept, although likely the health check shouldn't be doing that either. However, there was a bug where RAFT node skew would be detected for a consumer, it would be deleted, but not recreated if it was initially created within <10s. That's now fixed as well.
Signed-off-by: Maurice van Veen github@mauricevanveen.com