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From "Mark Miller (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SOLR-10525) Stacked recovery requests can interfere with one another
Date Wed, 19 Apr 2017 21:33:41 GMT

    [ https://issues.apache.org/jira/browse/SOLR-10525?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15975566#comment-15975566
] 

Mark Miller commented on SOLR-10525:
------------------------------------

Don't know if I answered Shalin's comment, but I've answered others about it. I'm sure that
is part of SOLR-8702 being filed, but seems no one has worked on it. The current strategy
was easy to get to from where were, and still very fast.

> Stacked recovery requests can interfere with one another
> --------------------------------------------------------
>
>                 Key: SOLR-10525
>                 URL: https://issues.apache.org/jira/browse/SOLR-10525
>             Project: Solr
>          Issue Type: Bug
>      Security Level: Public(Default Security Level. Issues are Public) 
>          Components: SolrCloud
>            Reporter: Mike Drob
>         Attachments: SOLR-10525.patch
>
>
> https://github.com/apache/lucene-solr/blob/master/solr/core/src/java/org/apache/solr/update/DefaultSolrCoreState.java#L300-L310
> Two issues with this code:
> {code}
>           boolean locked = recoveryLock.tryLock();
>           try {
>             if (!locked) {
>               if (recoveryWaiting.get() > 0) { // line 1
>                 return;
>               }
>               recoveryWaiting.incrementAndGet(); // line 2
>             } else {
>               recoveryWaiting.incrementAndGet();
>               cancelRecovery(); // line 3
> }
> {code}
> The {{cancelRecovery}} on line 3 call will only hit when there are no recoveries to actually
cancel (since we got the lock that means there are no recoveries in progress). Instead it
should be moved either to the either branch of the if, or outside after the if since we know
we will be running a recovery at that point.
> This code doesn't always prevent multiple requests from stacking. If there is a recovery
running, but no recoveries currently waiting, multiple requests can check the count at line
1 before any of them will increment the count at line 2 and thus all of them will hit the
increment.
> I don't have specific tests for this, but it's causing failures for me on my SOLR-9555
work in progress.



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