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https://issues.apache.org/jira/browse/SOLR-6763?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14219843#comment-14219843
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Alan Woodward commented on SOLR-6763:
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Yeah, I think the important thing to do here is to bail out on a
SessionExpiredException. So the added try-catch clause in the above patch will
fix it, but we want to keep the getChildren() call with retryOnReconnect=true.
> Shard leader election thread can persist across connection loss
> ---------------------------------------------------------------
>
> Key: SOLR-6763
> URL: https://issues.apache.org/jira/browse/SOLR-6763
> Project: Solr
> Issue Type: Bug
> Reporter: Alan Woodward
> Attachments: SOLR-6763.patch
>
>
> A ZK connection loss during a call to
> ElectionContext.waitForReplicasToComeUp() will result in two leader election
> processes for the shard running within a single node - the initial election
> that was waiting, and another spawned by the ReconnectStrategy. After the
> function returns, the first election will create an ephemeral leader node.
> The second election will then also attempt to create this node, fail, and try
> to put itself into recovery. It will also set the 'isLeader' value in its
> CloudDescriptor to false.
> The first election, meanwhile, is happily maintaining the ephemeral leader
> node. But any updates that are sent to the shard will cause an exception due
> to the mismatch between the cloudstate (where this node is the leader) and
> the local CloudDescriptor leader state.
> I think the fix is straightfoward - the call to zkClient.getChildren() in
> waitForReplicasToComeUp should be called with 'retryOnReconnect=false',
> rather than 'true' as it is currently, because once the connection has
> dropped we're going to launch a new election process anyway.
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