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From "Sanjay Radia (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-717) Proposal for exceptions thrown by FileContext and Abstract File System
Date Wed, 04 Nov 2009 19:43:32 GMT

    [ https://issues.apache.org/jira/browse/HDFS-717?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12773620#action_12773620
] 

Sanjay Radia commented on HDFS-717:
-----------------------------------

UnsupportedOperationException:

This one is tricky. See my comment in the rename jira: https://issues.apache.org/jira/browse/HADOOP-6240?focusedCommentId=12756632&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_12756632

Basically the argument is that folks routinely write applications that are to be deployed
on HDFS, but these apps are often tested  on the local file system.
Unfortunately, the unsupported exception will be thrown when testing the app.

Further wrt to setReplication, I think our API needs improvement: the setReplication operation
needs to be more abstract like "want redundancy" or "not want redundancy". No sure what the
API should look like.  A filesystem that uses raid can give you reliability by parity rather
than replication. I don't think it is a good idea to have setReplication throw UnsupportedOpsException.

Perhaps we should have methods like "IsFooOperationSupported()".

I am raising issues rather then offering answers.

> Proposal for exceptions thrown by FileContext and Abstract File System
> ----------------------------------------------------------------------
>
>                 Key: HDFS-717
>                 URL: https://issues.apache.org/jira/browse/HDFS-717
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Jitendra Nath Pandey
>            Assignee: Jitendra Nath Pandey
>             Fix For: 0.22.0
>
>
> Currently the APIs in FileContext throw only IOException. Going forward these APIs will
throw more specific exceptions.
> This jira proposes following hierarchy of exceptions to be thrown by FileContext and
AFS (Abstract File System) classes.
> InterruptedException  (java.lang.InterruptedException)
> IOException
>                 /* Following exceptions extend IOException */
>                 FileNotFoundException
>                 FileAlreadyExistsException
>                 DirectoryNotEmptyException
>                 NotDirectoryException
>                 AccessDeniedException
>                 IsDirectoryException
>                 InvalidPathNameException
>                 
>                 FileSystemException
>                                      /* Following exceptions extend FileSystemException
*/
>                                      FileSystemNotReadyException
>                                      ReadOnlyFileSystemException
>                                      QuotaExceededException
>                                      OutOfSpaceException
>                 RemoteException   (java.rmi.RemoteException)
> Most of the IOExceptions above are caused by invalid user input, while FileSystemException
is thrown when FS is in such a state that the requested operation cannot proceed.
> Please note that the proposed RemoteException is from standard java rmi package, which
also extends IOException.
>                             
> HDFS throws many exceptions which are not in the above list. The DFSClient will unwrap
the exceptions thrown by HDFS, and any exception not in the above list will be thrown as IOException
or FileSystemException.

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