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https://issues.apache.org/jira/browse/SOLR-8531?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15090720#comment-15090720
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Erick Erickson commented on SOLR-8531:
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Jeff:
Thanks for
1> persisting in figuring out what happened.
2> reporting it this comprehensively.
What did you do to fix this? I'm assuming that when the last old node is
upgraded somebody takes over leadership and if not the FORCELEADER could fix
that. And that if you aren't doing a rolling upgrade, i.e. you take the whole
cluster down, upgrade and bring the whole cluster up there aren't any problems.
I agree that you shouldn't have to do either of the above, mostly just making
sure I understand the ramifications.
[~markrmiller] any comments?
> ZK leader path changed in 5.4
> -----------------------------
>
> Key: SOLR-8531
> URL: https://issues.apache.org/jira/browse/SOLR-8531
> Project: Solr
> Issue Type: Bug
> Components: SolrCloud
> Affects Versions: 5.4
> Reporter: Jeff Wartes
>
> While doing a rolling upgrade from 5.3 to 5.4 of a solrcloud cluster, I
> observed that upgraded nodes would not register their shards as active unless
> they were elected the leader for the shard.
> There were no errors, the shards were fully up and responsive, but would not
> publish any change from the "down" state.
> This appears to be because the recovery process never happens, because the ZK
> node containing the current leader can't be found, because the ZK path has
> changed.
> Specifically, the leader data node changed from:
> <collection>/leaders/<shard>
> to
> <collection>/leaders/<shard>/leader
> It looks to me like this happened during SOLR-7844, perhaps accidentally.
> At the least, the "Migrating to Solr 5.4" section of the README should get
> updated with this info, since it means a rolling upgrade of a collection with
> multiple replicas will suffer serious degradation in the number of active
> replicas as nodes are upgraded. It's entirely possible this will reduce some
> shards to a single active replica.
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