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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-8676) Delayed rolling upgrade finalization can cause heartbeat expiration
Date Wed, 30 Sep 2015 14:43:04 GMT

    [ https://issues.apache.org/jira/browse/HDFS-8676?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14936917#comment-14936917
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Kihwal Lee commented on HDFS-8676:
----------------------------------

The patch looks good in general. There is a potential problem, which was part of the original
code.  There is a precondition check that can throw {{IllegalStateException}}, which is a
{{RuntimeException}}.  This can cause offerService() to blow up in the middle of heartbeat
response processing. For example, important command like {{DNA_ACCESSKEYUPDATE}} can be dropped.
 Instead of blowing up in the middle, it should log {{ERROR}} and move on.  I suggest changing
it to a combination of {{assert}} and conditional statement. {{assert}} will make sure it
blows up in testing, so we will know if something is obviously broken. In production, the
conditional statement will log the error message and simply skip the deletion.

> Delayed rolling upgrade finalization can cause heartbeat expiration
> -------------------------------------------------------------------
>
>                 Key: HDFS-8676
>                 URL: https://issues.apache.org/jira/browse/HDFS-8676
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: Kihwal Lee
>            Assignee: Walter Su
>            Priority: Critical
>         Attachments: HDFS-8676.01.patch
>
>
> In big busy clusters where the deletion rate is also high, a lot of blocks can pile up
in the datanode trash directories until an upgrade is finalized.  When it is finally finalized,
the deletion of trash is done in the service actor thread's context synchronously.  This blocks
the heartbeat and can cause heartbeat expiration.  
> We have seen a namenode losing hundreds of nodes after a delayed upgrade finalization.
 The deletion of trash directories should be made asynchronous.



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