[jira] [Created] (SOLR-13349) High CPU usage in Solr due to Java 8 bug

["Erick Erickson (JIRA)" <ji...@apache.org>]

Erick Erickson created SOLR-13349:
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             Summary: 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: 8.0, 7.7, 6.6, master (9.0)
            Reporter: Erick Erickson


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.

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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