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From "Uma Maheswara Rao G (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5299) DFS client hangs in updatePipeline RPC when failover happened
Date Sun, 06 Oct 2013 04:21:43 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5299?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13787488#comment-13787488

Uma Maheswara Rao G commented on HDFS-5299:

Thanks a lot Jing for addressing the comments.
+1 on the latest patch. Also thanks for the review Brandon.

> DFS client hangs in updatePipeline RPC when failover happened
> -------------------------------------------------------------
>                 Key: HDFS-5299
>                 URL: https://issues.apache.org/jira/browse/HDFS-5299
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 3.0.0, 2.1.0-beta
>            Reporter: Vinay
>            Assignee: Vinay
>            Priority: Blocker
>         Attachments: HDFS-5299.000.patch, HDFS-5299.patch
> DFSClient got hanged in updatedPipeline call to namenode when the failover happened at
exactly sametime.
> When we digged down, issue found to be with handling the RetryCache in updatePipeline.
> Here are the steps :
> 1. Client was writing slowly.
> 2. One of the datanode was down and updatePipeline was called to ANN.
> 3. Call reached the ANN, while processing updatePipeline call it got shutdown.
> 3. Now Client retried (Since the api marked as AtMostOnce) to another NameNode. at that
time still NN was in STANDBY and got StandbyException.
> 4. Now one more time client failover happened. 
> 5. Now SNN became Active.
> 6. Client called to current ANN again for updatePipeline, 
> Now client call got hanged in NN, waiting for the cached call with same callid to be
over. But this cached call is already got over last time with StandbyException.
> Conclusion :
> Always whenever the new entry is added to cache we need to update the result of the call
before returning the call or throwing exception.
> I can see similar issue multiple RPCs in FSNameSystem.

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