[jira] [Created] (HADOOP-16248) Fix MutableQuantiles memory leak

["Alexis Daboville (JIRA)" <ji...@apache.org>]

Alexis Daboville created HADOOP-16248:
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             Summary: Fix MutableQuantiles memory leak
                 Key: HADOOP-16248
                 URL: https://issues.apache.org/jira/browse/HADOOP-16248
             Project: Hadoop Common
          Issue Type: Bug
    Affects Versions: 2.9.2
            Reporter: Alexis Daboville
         Attachments: mutable-quantiles-leak.png, mutable-quantiles.patch

In some circumstances (high GC, high CPU usage, creating lots of
S3AFileSystem) it is possible for MutableQuantiles::scheduler [1] to fall
behind processing tasks that are submitted to it; because tasks are
submitted on a regular schedule, the unbounded queue backing the
{{ExecutorService}} might grow to several gigs [2]. By using
{{scheduleWithFixedDelay}} instead, we ensure that under pressure this leak won't
happen. In order to mitigate the growth, a simple fix is proposed, simply replacing {{scheduler.scheduleAtFixedRate}} by {{scheduler.scheduleWithFixedDelay}}.

[1] it is single threaded and shared across all instances of \{{MutableQuantiles}}: [https://github.com/apache/hadoop/blob/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/lib/MutableQuantiles.java#L66-L68]

[2] see attached mutable-quantiles-leak.



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