[HDFS-11395] RequestHedgingProxyProvider#RequestHedgingInvocationHandler hides the Exception thrown from NameNode

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.9.0, 3.0.0-alpha4, 2.8.2
• Component/s: ha
• Hadoop Flags: Reviewed
• Assignee: Nandakumar
• Reporter: Nandakumar
• Created: 07/Feb/17 15:12
• Updated: 21/Nov/17 01:13
• Resolved: 13/Mar/17 21:32

Description

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.

Issue Links

• breaks: HDFS-12813 RequestHedgingProxyProvider can hide Exception thrown from the Namenode for proxy size of 1