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From "Erik Krogen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-12323) NameNode terminates after full GC thinking QJM unresponsive if full GC is much longer than timeout
Date Tue, 12 Sep 2017 15:48:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-12323?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16163146#comment-16163146
] 

Erik Krogen commented on HDFS-12323:
------------------------------------

Thanks for the review [~shv]! Actually it is not possible to subclass {{QuorumCall}} (with
or without this patch) since all of its constructors are private (effectively a {{final}}
class), so that part of your concern does not apply. The point about reflection is interesting
but I am hesitant to add in dead code just to support a usage pattern on a private API that
probably shouldn't be encouraged anyhow. If you have strong feelings about this concern let
me know and I'll add the no-arg constructor.

> NameNode terminates after full GC thinking QJM unresponsive if full GC is much longer
than timeout
> --------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-12323
>                 URL: https://issues.apache.org/jira/browse/HDFS-12323
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode, qjm
>    Affects Versions: 2.7.4
>            Reporter: Erik Krogen
>            Assignee: Erik Krogen
>         Attachments: HDFS-12323.000.patch, HDFS-12323.001.patch
>
>
> HDFS-10733 attempted to fix the issue where the Namenode process would terminate itself
if it had a GC pause which lasted longer than the QJM timeout, since it would think that the
QJM had taken too long to respond. However, it only bumps up the timeout expiration by one
timeout length, so if the GC pause was e.g. 2x the length of the timeout, a TimeoutException
will be thrown and the NN will still terminate itself.
> Thanks to [~yangjiandan] for noting this issue as a comment on HDFS-10733; we have also
seen this issue on a real cluster even after HDFS-10733 is applied.



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