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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4061) Large number of decommission freezes the Namenode
Date Tue, 25 Nov 2008 01:08:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4061?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12650430#action_12650430
] 

Tsz Wo (Nicholas), SZE commented on HADOOP-4061:
------------------------------------------------

{noformat}
     [exec] +1 overall.  

     [exec]     +1 @author.  The patch does not contain any @author tags.

     [exec]     +1 tests included.  The patch appears to include 6 new or modified tests.

     [exec]     +1 javadoc.  The javadoc tool did not generate any warning messages.

     [exec]     +1 javac.  The applied patch does not increase the total number of javac compiler
warnings.

     [exec]     +1 findbugs.  The patch does not introduce any new Findbugs warnings.

     [exec]     +1 Eclipse classpath. The patch retains Eclipse classpath integrity.
{noformat}

> Large number of decommission freezes the Namenode
> -------------------------------------------------
>
>                 Key: HADOOP-4061
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4061
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.17.2
>            Reporter: Koji Noguchi
>            Assignee: Tsz Wo (Nicholas), SZE
>         Attachments: 4061_20081119.patch, 4061_20081120.patch, 4061_20081120b.patch,
4061_20081123.patch, 4061_20081124.patch, 4061_20081124b.patch, 4061_20081124c.patch, HADOOP-4061.patch
>
>
> On 1900 nodes cluster, we tried decommissioning 400 nodes with 30k blocks each. Other
1500 nodes were almost empty.
> When decommission started, namenode's queue overflowed every 6 minutes.
> Looking at the cpu usage,  it showed that every 5 minutes org.apache.hadoop.dfs.FSNamesystem$DecommissionedMonitor
thread was taking 100% of the CPU for 1 minute causing the queue to overflow.
> {noformat}
>   public synchronized void decommissionedDatanodeCheck() {
>     for (Iterator<DatanodeDescriptor> it = datanodeMap.values().iterator();
>          it.hasNext();) {
>       DatanodeDescriptor node = it.next();
>       checkDecommissionStateInternal(node);
>     }
>   }
> {noformat}

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