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https://issues.apache.org/jira/browse/HDFS-15822?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17279746#comment-17279746
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Kihwal Lee commented on HDFS-15822:
-----------------------------------
Hedged read has been known to be buggy. When there is an exception in one
datanode, it does not recover well. Multiple jiras have been filed in the past
regarding its flaws. e.g. HDFS-10597, HDFS-12971 and HDFS-15407. See if your
patch addresses the issues described there. You can dupe the Jira if you think
your change covers it.
> Client retry mechanism may invalid when use hedgedRead
> ------------------------------------------------------
>
> Key: HDFS-15822
> URL: https://issues.apache.org/jira/browse/HDFS-15822
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: hdfs-client
> Reporter: tianhang tang
> Assignee: tianhang tang
> Priority: Major
> Attachments: HDFS-15822.001.patch
>
>
> Hedgedread uses ignoreNodes to ensure that multiple requests fall on
> different nodes. But the ignoreNodes never been cleared. So if the request of
> 1st round all failed, and the refetched location is not changed, HDFS client
> would not request the same nodes which are in the ignoreNodes. It just sleep
> time by time until reach the retry num, then throw a exception.
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