Fix channel crash when cancelling then consuming using the same consumer tag and channel #5944
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kjnilsson
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By returning the next msg id for a merged consumer the rabbit_fifo_client can set it's next expected msg_id accordingly and avoid triggering a fetch of "missing" messages from the queue.
As since QQ v2 we don't ever keep any messages in memory and we need to read them from the log. The only way to do this is by using an aux command. Execute get_checked_out query on local members if possible This reduces the change of crashing a QQ member during a live upgrade where the follower does not have the appropriate code in handle_aux
michaelklishin
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Oct 4, 2022
Fix channel crash when cancelling then consuming using the same consumer tag and channel (backport #5944)
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This fixes a bug where the cancellation of a consumer then a subsequent consume with the same consumer tags whilst there are still messages in flight from the previous "incarnation" of the consumer would cause the channel to crash.
The reason for this was that the subsequent delivery would have an unexpected (for a new consumer) message id which would cause the channel to trigger the code paths it executes if a delivery got lost between the queue and the channel. This is extremely rare given most queue deliveries are done from the local node.
Triggering this code cause another bug where fetching messages would no longer work since 3.10 when messages stopped ever being kept in memory.
This PR fixes both bugs.
NB: it may seem like we are modifying the
rabbit_fifo:apply/3function without incrementing the machine version. We are but we are only modifying the Reply of the checkout command, not the actual state of the queue itself so this does not invalidate determinism. The current code never relies on the return value of this operation so this is safe to change as we also handle the old reply format.Fixes #5927