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Date: Fri, 10 Apr 2009 13:17:15 -0700 (PDT)
From: "Raghu Angadi (JIRA)" <jira@apache.org>
To: core-dev@hadoop.apache.org
Subject: [jira] Updated: (HADOOP-4584) Slow generation of blockReport at
 DataNode causes delay of sending heartbeat to NameNode
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     [ https://issues.apache.org/jira/browse/HADOOP-4584?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Raghu Angadi updated HADOOP-4584:
---------------------------------

       Resolution: Fixed
    Fix Version/s:     (was: 0.20.0)
                   0.21.0
     Release Note: 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.
           Status: Resolved  (was: Patch Available)

I just committed this. Thanks Suresh.

> 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: 0.21.0
>
>         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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