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https://issues.apache.org/jira/browse/HDFS-11395?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15890867#comment-15890867
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Jing Zhao commented on HDFS-11395:
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Thanks for working on this, [~nandakumar131]. I agree we should not directly
throw a MultiException. But I have similar concern as Arpit, i.e., we should
not simply throw the first exception. I think we should
# Not mix detailed exception handling logic into
{{RequestHedgingProxyProvider}}. In {{RequestHedgingProxyProvider}}, we only
need to get the RemoteException from {{ExecutionException}}, and put all the
exceptions into {{badResults}}. No need for special handling for
StandbyException etc there. These should be handled by
{{RetryInvocationHandler#newRetryInfo}}.
# Then in {{RetryInvocationHandler#newRetryInfo}}, we should let this method
return both the RetryInfo and the exception to throw from the MultiException.
These two information should comes from the same internal exception inside of
the MultiException.
> 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, HDFS-11395.001.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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