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From "Sangjin Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-12706) TestLocalFsFCStatistics#testStatisticsThreadLocalDataCleanUp times out occasionally
Date Wed, 13 Jan 2016 23:58:39 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-12706?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15097317#comment-15097317

Sangjin Lee commented on HADOOP-12706:

I was unable to reproduce it on my mac OS + JDK 1.7, but was able to reproduce it on ubuntu:

java version "1.7.0_91"
OpenJDK Runtime Environment (IcedTea 2.6.3) (7u91-2.6.3-0ubuntu0.15.10.1)
OpenJDK 64-Bit Server VM (build 24.91-b01, mixed mode)

The frequency is about 1 out of 20 - 30 iterations. My strong suspicion is whether System.gc()
would force the phantom reference to be enqueued in a timely manner. System.gc() itself is
not deterministic (it's only a hint to the JVM after all), and the manner in which the garbage
collector determines objects to be phantom-reachable seems to vary depending on the JVM/OS.

As [~cmccabe] and [~jlowe] observed, simply increasing the wait time in this case doesn't
seem to fix it.

I introduced a loop around GenericTestUtils.waitFor(), and if it times out I'm now forcing
another System.gc() call and trying again. I can verify that we do hit that condition, and
forcing another System.gc() call fixes it promptly. I ran the modified code 100 times on the
problem OS/JVM combination, and it now passes all 100 times.

I'll post a patch shortly.

> TestLocalFsFCStatistics#testStatisticsThreadLocalDataCleanUp times out occasionally
> -----------------------------------------------------------------------------------
>                 Key: HADOOP-12706
>                 URL: https://issues.apache.org/jira/browse/HADOOP-12706
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: test
>            Reporter: Jason Lowe
>            Assignee: Sangjin Lee
> TestLocalFsFCStatistics has been failing sometimes, and when it fails it appears to be
from FCStatisticsBaseTest.testStatisticsThreadLocalDataCleanUp.  The test is timing out when
it fails.

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