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https://issues.apache.org/jira/browse/HDFS-4093?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tsz Wo (Nicholas), SZE resolved HDFS-4093.
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Resolution: Fixed
Fix Version/s: 1-win
I have committed this. Thanks, Jing!
> In branch-1-win, AzureBlockPlacementPolicy#chooseTarget only returns one DN
> when replication factor is greater than 3.
> -----------------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-4093
> URL: https://issues.apache.org/jira/browse/HDFS-4093
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Jing Zhao
> Assignee: Jing Zhao
> Fix For: 1-win
>
> Attachments: HDFS-b1-win-4093.001.patch, HDFS-b1-win-4093.002.patch
>
>
> In branch-1-win, when AzureBlockPlacementPolicy (which extends the
> BlockPlacementPolicyDefault) is used, if the client increases the number of
> replicas (e.g., from 3 to 10), AzureBlockPlacementPolicy#chooseTarget will
> return only 1 Datanode each time. Thus in
> FSNameSystem#computeReplicationWorkForBlock, it is possible that the
> replication monitor may choose a datanode that has been chosen as target but
> still in the pendingReplications (because computeReplicationWorkForBlock does
> not check the pending replication before doing the chooseTarget).
> To avoid this "hit-the-same-datanode" scenario, we modify the
> AzureBlockPlacementPolicy#chooseTarget to make it return multiple DN.
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