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From "Suresh Srinivas (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-4584) Slow generation of blockReport at DataNode causes delay of sending heartbeat to NameNode
Date Fri, 03 Apr 2009 06:05:13 GMT

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

Suresh Srinivas updated HADOOP-4584:
------------------------------------

    Attachment: 4584.brthread.4.patch

Previous patch results in a bug where blocks are marked corrupt. In the patch, block report
is built by listing blocks from {{FSDataset.volumeMap}}. However the map has both finalized
and non-finalized blocks. The non-finalized blocks are reported with size set to the default
block size in the block report. When a last block is finalized, block received notification
to the name node reports the new size  smaller than previously reported. Namenode marks such
blocks as corrupt.

 The new patch adds only finalized blocks to the block report.


> 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 Core
>          Issue Type: Bug
>          Components: dfs
>            Reporter: Hairong Kuang
>            Assignee: Suresh Srinivas
>             Fix For: 0.20.0
>
>         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.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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