[FIXED] Race condition in some leader failover scenarios leading to messages being potentially sourced more than once. #4592
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We going to pull this in for 2.10.2? |
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derekcollison
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Sep 27, 2023
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…essages being potentially sourced more than once. - In some failure scenarios where the current leader of a stream sourcing from other stream(s) gets shutdown while publications are happening on the stream(s) being sourced leads to `setLeader(true)` being called on the new leader for the sourcing stream before all the messages having been sourced by the previous leader are completely processed such that when the new leader does it's reverse scan from the last message in it's view of the stream in order to know what sequence number to start the consumer for the stream being sourced from, such that the last message(s) sourced by the previous leader get sourced again, leading to some messages being sourced more than once. The existing `TestNoRaceJetStreamSuperClusterSources` test would sidestep the issue by relying on the deduplication window in the sourcing stream. Without deduplication the test is a flapper. This avoid the race condition by adding a small delay before scanning for the last message(s) having been sourced and starting the sources' consumer(s). Now the test (without using the deduplication window) never fails because more messages than expected have been received in the sourcing stream. - Fix test TestJetStreamWorkQueueSourceRestart that expects the sourcing stream to get all of the expected messages right away by adding a small sleep before checking the number of messages pending on the consumer for that stream. Signed-off-by: Jean-Noël Moyne <jnmoyne@gmail.com>
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If this runs green are we good to pull in? |
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Yes |
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git pull --rebase origin main)Changes proposed in this pull request:
Fixes a race condition in some leader failover scenarios leading to messages being potentially sourced more than once.
In some failure scenarios where the current leader of a stream sourcing from other stream(s) gets shutdown while publications are happening on the stream(s) being sourced leads to
setLeader(true)being called on the new leader for the sourcing stream before all the messages having been sourced by the previous leader are completely processed such that when the new leader does it's reverse scan from the last message in it's view of the stream in order to know what sequence number to start the consumer for the stream being sourced from, such that the last message(s) sourced by the previous leader get sourced again, leading to some messages being sourced more than once.The existing
TestNoRaceJetStreamSuperClusterSourcestest would sidestep the issue by relying on the deduplication window in the sourcing stream. Without deduplication the test is a flapper.This avoid the race condition by adding a small delay before scanning for the last message(s) having been sourced and starting the sources' consumer(s). Now the test (without using the deduplication window) never fails because more messages than expected have been received in the sourcing stream.
(Also adds a guard to give up if
setupSourceConsumers()is called and we are no longer the leader for the stream (that check was already present insetupMirrorConsumer()so assuming it was forgotten forsetupSourceConsumers())