[jira] Updated: (HADOOP-3339) DFS Write pipeline does not detect defective datanode correctly if it times out.

["Robert Chansler (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-3339?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Robert Chansler updated HADOOP-3339:
------------------------------------

    Release Note: 
Improved failure handling of last Data Node in write pipeline.


  was:
Some of the failures on 3rd datanode in DFS write pipelie are not detected properly. This could lead to hard failure of client's write operation.



> DFS Write pipeline does not detect defective datanode correctly if it times out.
> --------------------------------------------------------------------------------
>
>                 Key: HADOOP-3339
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3339
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.16.0
>            Reporter: Raghu Angadi
>            Assignee: Raghu Angadi
>             Fix For: 0.18.0
>
>         Attachments: HADOOP-3339.patch, tmp-3339-dn.patch
>
>
> When DFSClient is writing to DFS, it does not correctly detect the culprit datanode (rather datanodes do not inform) properly if the bad node times out. Say, the last datanode in in 3 node pipeline is is too slow or defective. In this case, pipeline removes the first two datanodes in first two attempts. The third attempt has only the 3rd datanode in the pipeline and it will fail too. If the pipeline detects the bad 3rd node when the first failure occurs, the write will succeed in the second attempt. 
> I will attach example logs of such cases. I think this should be fixed in 0.17.x.

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