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https://issues.apache.org/jira/browse/HDFS-13388?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16431908#comment-16431908
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SammiChen commented on HDFS-13388:
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Hi [~LiJinglun] and [~elgoiri], branch-2.9 suffers build failure with this
commit. Would you please double check it?
> 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, 2.9.2, 3.0.4
>
> 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
>
>
> 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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