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https://issues.apache.org/jira/browse/HDFS-13388?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16433855#comment-16433855
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Jinglun edited comment on HDFS-13388 at 4/11/18 12:41 PM:
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Hi [~elgoiri], I find a bug of 0006.patch: the InvocationTargetException isn't 
handled well so we can't get the correct Exception information when the proxy 
fails. My bad:(.  The fix is in 0007.patch. 


was (Author: lijinglun):
Hi [~elgoiri], I find a bug of 0006.patch: the InvocationTargetException isn't 
handled well so we can't get the correct Exception information when the proxy 
fails. My bad:(. 

> RequestHedgingProxyProvider calls multiple configured NNs all the time
> ----------------------------------------------------------------------
>
>                 Key: HDFS-13388
>                 URL: https://issues.apache.org/jira/browse/HDFS-13388
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs-client
>            Reporter: Jinglun
>            Assignee: Jinglun
>            Priority: Major
>             Fix For: 2.10.0, 3.2.0, 3.1.1
>
>         Attachments: HADOOP-13388.0001.patch, HADOOP-13388.0002.patch, 
> HADOOP-13388.0003.patch, HADOOP-13388.0004.patch, HADOOP-13388.0005.patch, 
> HADOOP-13388.0006.patch, HADOOP-13388.0007.patch
>
>
> In HDFS-7858 RequestHedgingProxyProvider was designed to "first 
> simultaneously call multiple configured NNs to decide which is the active 
> Namenode and then for subsequent calls it will invoke the previously 
> successful NN ." But the current code call multiple configured NNs every time 
> even when we already got the successful NN. 
>  That's because in RetryInvocationHandler.java, ProxyDescriptor's member 
> proxyInfo is assigned only when it is constructed or when failover occurs. 
> RequestHedgingProxyProvider.currentUsedProxy is null in both cases, so the 
> only proxy we can get is always a dynamic proxy handled by 
> RequestHedgingInvocationHandler.class. RequestHedgingInvocationHandler.class 
> handles invoked method by calling multiple configured NNs.



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