[jira] [Comment Edited] (HDFS-11395) RequestHedgingProxyProvider#RequestHedgingInvocationHandler hides the Exception thrown from NameNode

["Jing Zhao (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-11395?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15890867#comment-15890867 ] 

Jing Zhao edited comment on HDFS-11395 at 3/1/17 7:27 PM:
----------------------------------------------------------

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.


was (Author: jingzhao):
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.



--
This message was sent by Atlassian JIRA
(v6.3.15#6346)

---------------------------------------------------------------------
To unsubscribe, e-mail: hdfs-issues-unsubscribe@hadoop.apache.org
For additional commands, e-mail: hdfs-issues-help@hadoop.apache.org