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https://issues.apache.org/jira/browse/SOLR-7989?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15002241#comment-15002241
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Ishan Chattopadhyaya commented on SOLR-7989:
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bq. I don't think this is a valid test at all. Why does it clear LIR while
Solr is running? That is not a valid real world scenario.
Indeed, that's why I didn't include it in the patch. I just wanted to bring out
that there is a problem, but then I couldn't replicate it in a test in any
other way that represents a real world situation. However, just that fact that
there were two messages passed as one (LEADER message had a state param)
indicated to me that we should, in theory, split them out.
+1 to your patch, I hadn't considered the core registration scenario. Also, the
change from only DOWN to ACTIVE makes sense, and excluding the RECOVERING to
ACTIVE change.
> Down replica elected leader, stays down after successful election
> -----------------------------------------------------------------
>
> Key: SOLR-7989
> URL: https://issues.apache.org/jira/browse/SOLR-7989
> Project: Solr
> Issue Type: Bug
> Reporter: Ishan Chattopadhyaya
> Assignee: Mark Miller
> Fix For: 5.4, Trunk
>
> Attachments: DownLeaderTest.java, DownLeaderTest.java,
> SOLR-7989.patch, SOLR-7989.patch, SOLR-7989.patch, SOLR-7989.patch,
> SOLR-7989.patch, SOLR-7989.patch, SOLR-7989.patch, SOLR-8233.patch
>
>
> It is possible that a down replica gets elected as a leader, and that it
> stays down after the election.
> Here's how I hit upon this:
> * There are 3 replicas: leader, notleader0, notleader1
> * Introduced network partition to isolate notleader0, notleader1 from leader
> (leader puts these two in LIR via zk).
> * Kill leader, remove partition. Now leader is dead, and both of notleader0
> and notleader1 are down. There is no leader.
> * Remove LIR znodes in zk.
> * Wait a while, and there happens a (flawed?) leader election.
> * Finally, the state is such that one of notleader0 or notleader1 (which were
> down before) become leader, but stays down.
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