[
https://issues.apache.org/jira/browse/HDFS-11395?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15880162#comment-15880162
]
Nandakumar commented on HDFS-11395:
-----------------------------------
{quote}
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.
{quote}
Yeah, true. Short-circuit failure path in RequestHedgingInvocationHandler is
not a proper solution here.
I had a look at RetryInvocationHandler, MultiException is handled only while
constructing RetryInfo in RetryInvocationHandler#RetryInfo#newRetryInfo.
In {{RetryInvocationHandler#handleException}} if {{retryInfo.fail != null}} the
received exception is thrown as it is, which in our case is
MultiException(ExecutionException(RemoteException(Exception)))
As you suggested, we can unwrap ExecutionException and throw
MultiException(RemoteException(Exception)) from RequestHedgingInvocationHandler.
We still have to handle MultiException in RetryInvocationHandler.
In RetryInvocationHandler, we will get list of RemoteExceptions' from
MultiException, from which we can exclude StandbyExceptions'. Is there any
other check that can be performed to identify the proper exception to throw
back to client?
> 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.
--
This message was sent by Atlassian JIRA
(v6.3.15#6346)
---------------------------------------------------------------------
To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org
For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org
