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https://issues.apache.org/jira/browse/HADOOP-5479?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13181970#comment-13181970
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Thanh Do commented on HADOOP-5479:
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Hi Hairong,
This is an old issue but could you please verify my understanding about this
bug? So basically, because the NN keeps send empty replication command, the DN
creates a new thread for every empty command, which eats up DN's resource,
right?
Many thanks
> NameNode should not send empty block replication request to DataNode
> --------------------------------------------------------------------
>
> Key: HADOOP-5479
> URL: https://issues.apache.org/jira/browse/HADOOP-5479
> Project: Hadoop Common
> Issue Type: Bug
> Reporter: Hairong Kuang
> Assignee: Hairong Kuang
> Priority: Critical
> Fix For: 0.19.2, 0.20.0
>
> Attachments: numTransfers.patch, numTransfers1.patch
>
>
> On our production clusters, we occasionally see that NameNode sends an empty
> block replication request to DataNode on every heartbeat, thus blocking this
> DataNode from replicating or deleting any block.
> This is partly caused by DataNode sending a wrong number of replications in
> progress which will be fixed by HADOOP-5465. There is also a flaw at the
> NameNode side. NameNode should not interpret the number of replications in
> progress as the number of targets since replication is done through a
> pipeline. It also should make sure that no empty replication request is sent
> to DataNode.
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