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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 Thu, 12 Mar 2009 22:42:50 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.2.patch

Couple of changes that requires careful review:
# Currently metadata file exists without a corresponding block is deleted. Could this cause
a problem (that is if metadata file was created before a block file is created)?
# DirectoryScanner is added to DataBlockScanner. While reconciling the difference between
the disk and in-memory blocks, existing scanner functionality is suspended. Would this cause
problem for DataBlockScanner in ensuring its constraints such as scanning with in certain
period of time and using configured bandwidth?

> 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.hbthread.patch, 4584.patch, 4584.patch,
4584.patch, 4584.patch, 4584.patch, 4584.patch
>
>
> 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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