[jira] [Created] (CASSANDRA-20659) Gossip doesn't converge due to race condition when updating EndpointStates multiple fields

["David Capwell (Jira)" <ji...@apache.org>]

David Capwell created CASSANDRA-20659:
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             Summary: 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


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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