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From "Robert Chansler (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-4584) Slow generation of blockReport at DataNode causes delay of sending heartbeat to NameNode
Date Fri, 09 Oct 2009 04:07:31 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-4584?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Robert Chansler updated HADOOP-4584:
------------------------------------

    Release Note:   (was: Improve datanode block reports and associated file system scan to
avoid interefering with normal datanode operations. Large datanodes with many block should
be handled much better now.)

Editorial pass over all release notes prior to publication of 0.21. Bug.

> Slow generation of blockReport at DataNode causes delay of sending heartbeat to NameNode
> ----------------------------------------------------------------------------------------
>
>                 Key: HADOOP-4584
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4584
>             Project: Hadoop Common
>          Issue Type: Bug
>            Reporter: Hairong Kuang
>            Assignee: Suresh Srinivas
>             Fix For: 0.21.0
>
>         Attachments: 4584.brthread.2.patch, 4584.brthread.3.patch, 4584.brthread.3.patch,
4584.brthread.3.patch, 4584.brthread.3.patch, 4584.brthread.3.patch, 4584.brthread.4.patch,
4584.brthread.4.patch, 4584.brthread.4.patch, 4584.brthread.5.patch, 4584.brthread.5.patch,
4584.hbthread.patch, 4584.patch, 4584.patch, 4584.patch, 4584.patch, 4584.patch, 4584.patch,
Design.pdf, Design.pdf
>
>
> sometimes due to disk or some other problems, datanode takes minutes or tens of minutes
to generate a block report. It causes the datanode not able to send heartbeat to NameNode
every 3 seconds. In the worst case, it makes NameNode to detect a lost heartbeat and wrongly
decide that the datanode is dead.
> It would be nice to have two threads instead. One thread is for scanning data directories
and generating block report, and executes the requests sent by NameNode; Another thread is
for sending heartbeats, block reports, and picking up the requests from NameNode. By having
these two threads, the sending of heartbeats will not get delayed by any slow block report
or slow execution of NameNode requests.

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