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https://issues.apache.org/jira/browse/SOLR-13349?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16846744#comment-16846744
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Cassandra Targett commented on SOLR-13349:
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Yes, 7.7.2 is coming very soon - within the next couple of weeks.

> High CPU usage in Solr due to Java 8 bug
> ----------------------------------------
>
>                 Key: SOLR-13349
>                 URL: https://issues.apache.org/jira/browse/SOLR-13349
>             Project: Solr
>          Issue Type: Improvement
>      Security Level: Public(Default Security Level. Issues are Public) 
>    Affects Versions: 7.7, 8.0, master (9.0)
>            Reporter: Erick Erickson
>            Assignee: Erick Erickson
>            Priority: Major
>             Fix For: 7.7.2, 8.1, master (9.0)
>
>         Attachments: SOLR-13349.patch
>
>
> We've had sporadic reports of high CPU usage in Solr 7. Lukas Weiss reported 
> a Java 8 bug that appears to be the root cause (I have not personally 
> verified), see: [https://bugs.openjdk.java.net/browse/JDK-8129861] e-mail 
> reproduced below:
> CommitTracker makes this call:
> Executors.newScheduledThreadPool(0, new 
> DefaultSolrThreadFactory("commitScheduler"));
> The supposition is that calling this with 1 will fix this (untested)
> [~ichattopadhyaya] This affects 6.6 and IIUC you're spinning a new version. 
> We'll need to verify and include this fix.
> [~jpountz] You're right. I first thought "naaah, it wouldn't be that far 
> back" but your question made me check, thanks!
> AFAICT, this is the only place in Solr/Lucene that uses zero.
> Using Java 9+ is another work-around.
> Anyone picking this up should port to 7.7 as well.
> e-mail from the user's list (many thanks to Lukas and Adam).
> Apologies, I can’t figure out how to reply to the Solr mailing list.
>  I just ran across the same high CPU usage issue. I believe it’’s caused by 
>  this commit which was introduced in Solr 7.7.0 
>  
> [https://github.com/apache/lucene-solr/commit/eb652b84edf441d8369f5188cdd5e3ae2b151434#diff-e54b251d166135a1afb7938cfe152bb5]
>  There is a bug in JDK versions <=8 where using 0 threads in the 
>  ScheduledThreadPool causes high CPU usage: 
>  [https://bugs.openjdk.java.net/browse/JDK-8129861]
>  Oddly, the latest version 
>  of solr/core/src/java/org/apache/solr/update/CommitTracker.java on 
>  master still uses 0 executors as the default. Presumably most everyone is 
>  using JDK 9 or greater which has the bug fixed, so they don’t experience 
>  the bug.
>  Feel free to relay this back to the mailing list.
>  Thanks,
>  Adam Guthrie
>  
>  



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