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https://issues.apache.org/jira/browse/SOLR-5615?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13864491#comment-13864491
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Ramkumar Aiyengar commented on SOLR-5615:
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Fair enough. Would that allow multiple onReconnect.command () invocations to
run simultaneously, and is that fine? (on mobile, so my reading of the patch
could be wrong) What if we were in the process of recovering when we were
unfortunate enough to get a second expiry thereby bringing all nodes down?
> Deadlock while trying to recover after a ZK session expiry
> ----------------------------------------------------------
>
> Key: SOLR-5615
> URL: https://issues.apache.org/jira/browse/SOLR-5615
> Project: Solr
> Issue Type: Bug
> Components: SolrCloud
> Affects Versions: 4.4, 4.5, 4.6
> Reporter: Ramkumar Aiyengar
> Assignee: Mark Miller
> Fix For: 5.0, 4.7, 4.6.1
>
> Attachments: SOLR-5615.patch, SOLR-5615.patch
>
>
> The sequence of events which might trigger this is as follows:
> - Leader of a shard, say OL, has a ZK expiry
> - The new leader, NL, starts the election process
> - NL, through Overseer, clears the current leader (OL) for the shard from
> the cluster state
> - OL reconnects to ZK, calls onReconnect from event thread (main-EventThread)
> - OL marks itself down
> - OL sets up watches for cluster state, and then retrieves it (with no
> leader for this shard)
> - NL, through Overseer, updates cluster state to mark itself leader for the
> shard
> - OL tries to register itself as a replica, and waits till the cluster state
> is updated
> with the new leader from event thread
> - ZK sends a watch update to OL, but it is blocked on the event thread
> waiting for it.
> Oops. This finally breaks out after trying to register itself as replica
> times out after 20 mins.
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