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https://issues.apache.org/jira/browse/HDFS-5946?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13900678#comment-13900678
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Alejandro Abdelnur commented on HDFS-5946:
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You get data locality only for the first block of the file, for subsequent
blocks you are stuck to the DN serving the file via webhdfs.
> Webhdfs DN choosing code is flawed
> ----------------------------------
>
> Key: HDFS-5946
> URL: https://issues.apache.org/jira/browse/HDFS-5946
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode, webhdfs
> Affects Versions: 3.0.0, 2.4.0
> Reporter: Daryn Sharp
> Priority: Critical
>
> HDFS-5891 improved the performance of redirecting webhdfs clients to a DN.
> Instead of attempting a connection with a 1-minute timeout, the NN skips
> decommissioned nodes.
> The logic appears flawed. It finds the index of the first decommissioned
> node, if any, then:
> * Throws an exception if index = 0, even if other nodes later in the list are
> not decommissioned.
> * Else picks a random node prior to the index. Let's say there are 10
> replicas, 2nd location is decommissioned. All clients will be redirected to
> the first location even though there are 8 other valid locations.
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