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[CI] testLeaderDisconnectionWithoutDisconnectEventDetectedQuickly failure #53271

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hendrikmuhs opened this issue Mar 9, 2020 · 2 comments · Fixed by #53338
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[CI] testLeaderDisconnectionWithoutDisconnectEventDetectedQuickly failure #53271

hendrikmuhs opened this issue Mar 9, 2020 · 2 comments · Fixed by #53338
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@DaveCTurner
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:Distributed Coordination/Cluster Coordination Cluster formation and cluster state publication, including cluster membership and fault detection. >test-failure Triaged test failures from CI

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@hendrikmuhs
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log:https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+master+multijob-unix-compatibility/os=ubuntu-18.04&&immutable/622/console
gradle:https://gradle-enterprise.elastic.co/s/olunhuu5qmlyk

reproduces locally

failure:

 2> REPRODUCE WITH: ./gradlew ':server:test' --tests "org.elasticsearch.cluster.coordination.CoordinatorTests.testLeaderDisconnectionWithoutDisconnectEventDetectedQuickly" -Dtests.seed=30C7DB320E81F553 -Dtests.security.manager=true -Dtests.locale=es-VE -Dtests.timezone=Australia/Currie -Dcompiler.java=13
  2> java.lang.AssertionError: node0 is a follower of node4
    Expected: is <FOLLOWER>
         but: was <CANDIDATE>
        at __randomizedtesting.SeedInfo.seed([30C7DB320E81F553:2208AF1950E0880]:0)
        at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:18)
        at org.junit.Assert.assertThat(Assert.java:956)
        at org.elasticsearch.cluster.coordination.AbstractCoordinatorTestCase$Cluster.stabilise(AbstractCoordinatorTestCase.java:530)
        at org.elasticsearch.cluster.coordination.AbstractCoordinatorTestCase$Cluster.stabilise(AbstractCoordinatorTestCase.java:490)
        at org.elasticsearch.cluster.coordination.CoordinatorTests.testLeaderDisconnectionWithoutDisconnectEventDetectedQuickly(CoordinatorTests.java:409)
  2> NOTE: leaving temporary files on disk at: /home/hendrik/work/git-elastic-prod/elasticsearch/server/build/testrun/test/temp/org.elasticsearch.cluster.coordination.CoordinatorTests_30C7DB320E81F553-003
  2> NOTE: test params are: codec=Lucene84, sim=Asserting(org.apache.lucene.search.similarities.AssertingSimilarity@407d2d52), locale=es-VE, timezone=Australia/Currie
  2> NOTE: Linux 5.3.0-40-generic amd64/AdoptOpenJDK 13.0.2 (64-bit)/cpus=16,threads=1,free=464710688,total=536870912
  2> NOTE: All tests run in this JVM: [CoordinatorTests]

repro:

./gradlew ':server:test' --tests "org.elasticsearch.cluster.coordination.CoordinatorTests.testLeaderDisconnectionWithoutDisconnectEventDetectedQuickly" \
  -Dtests.seed=30C7DB320E81F553 \
  -Dtests.security.manager=true \
  -Dtests.locale=es-VE \
  -Dtests.timezone=Australia/Currie \
  -Dcompiler.java=13
@hendrikmuhs hendrikmuhs added >test-failure Triaged test failures from CI :Distributed Coordination/Cluster Coordination Cluster formation and cluster state publication, including cluster membership and fault detection. labels Mar 9, 2020
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Pinging @elastic/es-distributed (:Distributed/Cluster Coordination)

@DaveCTurner DaveCTurner self-assigned this Mar 9, 2020
@DaveCTurner
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Ohh this is tricky.

The test fails in the first stabilise() method, before any disruptions took place. node0 is rejecting publications from the leader (node4) because node0 is in term 2 but node4 is in term 1.

The trouble is that node4 tried to trigger an election in term 2 and broadcasts a start-join request, but fails to process it locally due to a (simulated) IO exception, so it remains in term 1. Meanwhile node0 receives and processes the start-join request successfully, votes for node4 and enters term 2. Then node4 becomes leader in term 1 anyway.

Publication#onMissingJoin deals with the case where a publication was accepted by a node that voted for a different master in this term by triggering a term bump. However here node0 is forced to reject the publication since it's in a stale term, so we do not trigger the term bump.

DaveCTurner added a commit to DaveCTurner/elasticsearch that referenced this issue Mar 10, 2020
@DaveCTurner
Allow joining node to trigger term bump
045f53a 
In rare circumstances it is possible for an isolated node to have a greater
term than the currently-elected leader. Today such a node will attempt to join
the cluster but will not offer a vote to the leader and will reject its cluster
state publications due to their stale term. This situation persists since there
is no mechanism for the joining node to inform the leader that its term is
stale and a new election is required.

This commit adds the current term of the joining node to the join request. Once
the join has been validated, the leader will perform another election to
increase its term far enough to allow the isolated node to join properly.

Fixes elastic#53271
@DaveCTurner DaveCTurner mentioned this issue Mar 10, 2020
Merged
DaveCTurner added a commit that referenced this issue Mar 11, 2020
@DaveCTurner
Allow joining node to trigger term bump (#53338)
9dcd88e 
In rare circumstances it is possible for an isolated node to have a greater
term than the currently-elected leader. Today such a node will attempt to join
the cluster but will not offer a vote to the leader and will reject its cluster
state publications due to their stale term. This situation persists since there
is no mechanism for the joining node to inform the leader that its term is
stale and a new election is required.

This commit adds the current term of the joining node to the join request. Once
the join has been validated, the leader will perform another election to
increase its term far enough to allow the isolated node to join properly.

Fixes #53271
DaveCTurner added a commit that referenced this issue Mar 11, 2020
@DaveCTurner
Allow joining node to trigger term bump (#53338)
ac72193 
In rare circumstances it is possible for an isolated node to have a greater
term than the currently-elected leader. Today such a node will attempt to join
the cluster but will not offer a vote to the leader and will reject its cluster
state publications due to their stale term. This situation persists since there
is no mechanism for the joining node to inform the leader that its term is
stale and a new election is required.

This commit adds the current term of the joining node to the join request. Once
the join has been validated, the leader will perform another election to
increase its term far enough to allow the isolated node to join properly.

Fixes #53271
@codebrain codebrain mentioned this issue Apr 1, 2020
Closed
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:Distributed Coordination/Cluster Coordination Cluster formation and cluster state publication, including cluster membership and fault detection. >test-failure Triaged test failures from CI
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Allow joining node to trigger term bump DaveCTurner/elasticsearch
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@DaveCTurner @hendrikmuhs @elasticmachine