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