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https://issues.apache.org/jira/browse/HDFS-11395?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15878972#comment-15878972
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Arpit Agarwal commented on HDFS-11395:
--------------------------------------
Hi [~nandakumar131], RetryInvocationHandler has some logic for unwrapping
MultiException ([code
here|https://github.com/apache/hadoop/blob/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/retry/RetryInvocationHandler.java#L267]).
I haven't looked at it carefully so don't know if it does the right thing.
Deciding what to do when we get a MultiException should probably be handled in
the RetryInvocationHandler.
The reason the short-circuit failure path looks incorrect is because it can
cause spurious request failures if the standby thinks it is active and throws
something other than StandbyException.
> RequestHedgingProxyProvider#RequestHedgingInvocationHandler hides the
> Exception thrown from NameNode
> ----------------------------------------------------------------------------------------------------
>
> Key: HDFS-11395
> URL: https://issues.apache.org/jira/browse/HDFS-11395
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: ha
> Reporter: Nandakumar
> Assignee: Nandakumar
> Attachments: HDFS-11395.000.patch
>
>
> When using RequestHedgingProxyProvider, in case of Exception (like
> FileNotFoundException) from ActiveNameNode,
> {{RequestHedgingProxyProvider#RequestHedgingInvocationHandler.invoke}}
> receives {{ExecutionException}} since we use {{CompletionService}} for the
> call. The ExecutionException is put into a map and wrapped with
> {{MultiException}}.
> So for a FileNotFoundException the client receives
> {{MultiException(Map(ExecutionException(InvocationTargetException(RemoteException(FileNotFoundException)))))}}
> It will cause problem in clients which are handling RemoteExceptions.
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