Donny Nadolny created ZOOKEEPER-2204:
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Summary:
LearnerSnapshotThrottlerTest.testHighContentionWithTimeout fails occasionally
Key: ZOOKEEPER-2204
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2204
Project: ZooKeeper
Issue Type: Test
Affects Versions: 3.5.0
Reporter: Donny Nadolny
Assignee: Donny Nadolny
Priority: Minor
The {{LearnerSnapshotThrottler}} will only allow 2 concurrent snapshots to be
taken, and if there are already 2 snapshots in progress it will wait up to
200ms for one to complete. This isn't enough time for
{{testHighContentionWithTimeout}} to consistently pass - on a cold JVM running
just the one test I was able to get it to fail 3 times in around 50 runs. This
200ms timeout will be hit if there is a delay between a thread calling
{{LearnerSnapshot snap = throttler.beginSnapshot(false);}} and
{{throttler.endSnapshot();}}.
This also erroneously fails on the build server, see
https://builds.apache.org/job/PreCommit-ZOOKEEPER-Build/2747/testReport/org.apache.zookeeper.server.quorum/LearnerSnapshotThrottlerTest/testHighContentionWithTimeout/
for an example.
I have bumped the timeout up to 5 seconds (which should be more than enough for
warmup / gc pauses), as well as added logging to the {{catch (Exception e)}}
block to assist in debugging any future issues.
An alternate approach would be to separate out results gathered from the
threads, because although we only record true/false there are really three
outcomes:
1. The {{snapshotNumber}} was <= 2, meaning the individual call operated
correctly
2. The {{snapshotNumber}} was > 2, meaning the test should definitely fail
3. We were unable to snapshot in the time given, so we can't determine if we
should fail or pass (although if we have "enough" successes from #1 with no
failures from #2 maybe we would pass the test anyway).
Bumping up the timeout is easier.
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