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https://issues.apache.org/jira/browse/HDFS-5299?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13787413#comment-13787413
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Brandon Li commented on HDFS-5299:
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+1. Patch looks good.
> 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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