Quorum Queue consumer cancellation fixes (backport #3448) #3460
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If the queue is empty when a consumer is cancelled it would leave the consumer id inside the service queue. If an application subscribes/unsubscibes in a loop from an empty queue this would cause the service queue to never be cleared up. NB: whenever we make a change to how the quorum queue state machien is calculated we need to consider how this effects determinism as during an upgrade different members may calculate a different service queue state. In this case it should be ok as they will eventually converge on the same state once all "dead" consumer ids have been removed from the queue. In any case it should not affect how messages are assigned to consumers. (cherry picked from commit 5779059)
If this is not done apps that consume/cancel from empty queues in a loop will grow the raft log in an unbounded manner. This could also be the case for the garbage_collect command. (cherry picked from commit eaa216d)
It should be rare that repeated use of these commands would grow the Raft log excessively but just incase we evaluate the release cursors here anyway so that if the queue is empty we may trigger a snapshot anyway. (cherry picked from commit ee6ef35)
acogoluegnes
approved these changes
Sep 21, 2021
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This is an automatic backport of pull request #3448 done by Mergify.
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