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https://issues.apache.org/jira/browse/HDFS-795?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Todd Lipcon resolved HDFS-795.
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Resolution: Duplicate
HDFS-101 duplicates this, and fix is under way there.
> DFS Write pipeline does not detect defective datanode correctly in some cases
> (HADOOP-3339)
> -------------------------------------------------------------------------------------------
>
> Key: HDFS-795
> URL: https://issues.apache.org/jira/browse/HDFS-795
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: hdfs client
> Affects Versions: 0.20.1
> Reporter: Raghu Angadi
> Priority: Critical
> Fix For: 0.20.2
>
> Attachments: toreproduce-5796.patch
>
>
> HDFS write pipeline does not select the correct datanode in some error cases.
> One example : say DN2 is the second datanode and write to it times out since
> it is in a bad state.. pipeline actually removes the first datanode. If such
> a datanode happens to be the last one in the pipeline, write is aborted
> completely with a hard error.
> Essentially the error occurs when writing to a downstream datanode fails
> rather than reading. This bug was actually fixed in 0.18 (HADOOP-3339). But
> HADOOP-1700 essentially reverted it. I am not sure why.
> It is absolutely essential for HDFS to handle failures on subset of datanodes
> in a pipeline. We should not have at least known bugs that lead to hard
> failures.
> I will attach patch for a hack that illustrates this problem. Still thinking
> of how an automated test would look like for this one.
> My preferred target for this fix is 0.20.1.
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