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From "Vinay (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5177) blocksScheduled count should be decremented for abandoned blocks
Date Tue, 04 Feb 2014 17:22:11 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5177?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13890869#comment-13890869

Vinay commented on HDFS-5177:

Hi all,
Can someone please take a look at the patch.
Thanks in advance.

> blocksScheduled  count should be decremented for abandoned blocks
> -----------------------------------------------------------------
>                 Key: HDFS-5177
>                 URL: https://issues.apache.org/jira/browse/HDFS-5177
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 3.0.0, 2.1.0-beta
>            Reporter: Vinay
>            Assignee: Vinay
>         Attachments: HDFS-5177.patch, HDFS-5177.patch, HDFS-5177.patch
> DatanodeDescriptor#incBlocksScheduled() will be called for all datanodes of the block
on each allocation. But same should be decremented for abandoned blocks.
> When one of the datanodes is down and same is allocated for the block along with other
live datanodes, then this block will be abandoned, but the scheduled count on other datanodes
will consider live datanodes as loaded, but in reality these datanodes may not be loaded.
> Anyway this scheduled count will be rolled every 20 mins.
> Problem will come if the rate of creation of files is more. Due to increase in the scheduled
count, there might be chances of missing local datanode to write to. and some times writes
also can fail in small clusters.
> So we need to decrement the unnecessary count on abandon block call.

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