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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-5134) FSNamesystem#commitBlockSynchronization adds under-construction block locations to blocksMap
Date Wed, 11 Feb 2009 19:18:59 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-5134?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12672734#action_12672734
] 

dhruba borthakur commented on HADOOP-5134:
------------------------------------------

This patch had nothing much to do with "appends", but it has mightily related to datanode(s)
dropping off the write-pipeline during a write form a client.

When a client is writing to a file and encounters an error (bad datanode in pipleine), it
invokes commitBlockSync(). This patch guarantees that this call to commitBlockSyn() does not
add any replicas to the blocksMap. That's what you wanted, isn't it?

> FSNamesystem#commitBlockSynchronization adds under-construction block locations to blocksMap
> --------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-5134
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5134
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.18.2
>            Reporter: Hairong Kuang
>            Assignee: dhruba borthakur
>            Priority: Blocker
>             Fix For: 0.18.4
>
>         Attachments: commitBlockSync.patch
>
>
> From my understanding of sync/append design, an under construction block should not have
any block locations associated with it in the blocksMap. So an under construction block will
not be managed by ReplicationMonitor.
> However, if there is an error in the write pipeline, a lease recovery will trigger a
call, commitBlockSynchronization, to NN. This call will add the successfully-recovered datanodes
to blocksMap. This seems to violate the design. It should update the targets of the last block
at INode instead. 

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