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https://issues.apache.org/jira/browse/CASSANDRA-20659?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17953230#comment-17953230
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Brandon Williams commented on CASSANDRA-20659:
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4.x/5 branches look good, +1 if CI is happy too.
> Gossip doesn't converge due to race condition when updating EndpointStates
> multiple fields
> ------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-20659
> URL: https://issues.apache.org/jira/browse/CASSANDRA-20659
> Project: Apache Cassandra
> Issue Type: Bug
> Components: Cluster/Gossip
> Reporter: David Capwell
> Assignee: David Capwell
> Priority: Normal
> Fix For: 4.1.x, 5.0.x, 5.x
>
> Time Spent: 40m
> Remaining Estimate: 0h
>
> The issue seen is during shrinks or token moves the cluster gets into a state
> where some of the nodes never converge and see the latest STATUS state for
> the changed peers.
> In testing this it was found that:
> 1) org.apache.cassandra.gms.Gossiper#applyStateLocally expects to run in a
> single thread, so doesn't take any locks
> 2) org.apache.cassandra.gms.Gossiper.GossipTask runs in another thread and
> uses a taskLock to avoid sending partial state
> 3) org.apache.cassandra.gms.Gossiper#applyNewStates gets called when the
> generation matches, and tries to apply the state sequentially.
> The theory (and test) is
> 1) localState.setHeartBeatState(remoteState.getHeartBeatState()); runs
> 2) something (gossip or paxos) read the state
> 3) localState.addApplicationStates(updatedStates); updates the state
> the "something" in step 2 sends around the heartbeat which cause others to
> see a higher max version, so the delta logic won't see the mutations done in
> step 3
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