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Date: Tue, 14 Mar 2017 22:38:41 +0000 (UTC)
From: "James Clampffer (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.13055878.1489482305000.20372.1489531121577@Atlassian.JIRA>
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Subject: [jira] [Commented] (HDFS-11529) libHDFS still does not return
 appropriate error information in many cases
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archived-at: Tue, 14 Mar 2017 22:38:46 -0000


    [ https://issues.apache.org/jira/browse/HDFS-11529?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15925183#comment-15925183 ] 

James Clampffer commented on HDFS-11529:
----------------------------------------

We added a "hdfsGetLastError" call using thread local state like you're proposing in the C API for libhdfs++ (HDFS-8707).  It's been very useful in practice for HDFS stuff that doesn't map directly to posix errnos.

> libHDFS still does not return appropriate error information in many cases
> -------------------------------------------------------------------------
>
>                 Key: HDFS-11529
>                 URL: https://issues.apache.org/jira/browse/HDFS-11529
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: libhdfs
>    Affects Versions: 2.6.0
>            Reporter: Sailesh Mukil
>            Priority: Critical
>              Labels: errorhandling, libhdfs
>
> libHDFS uses a table to compare exceptions against and returns a corresponding error code to the application in case of an error.
> However, this table is manually populated and many times is disremembered when new exceptions are added.
> This causes libHDFS to return EINTERNAL (or Unknown Error(255)) whenever these exceptions are hit. These are some examples of exceptions that have been observed on an Error(255):
> org.apache.hadoop.ipc.StandbyException (Operation category WRITE is not supported in state standby)
> java.io.EOFException: Cannot seek after EOF
> javax.security.sasl.SaslException: GSS initiate failed [Caused by GSSException: No valid credentials provided (Mechanism level: Failed to find any Kerberos tgt)
> It is of course not possible to have an error code for each and every type of exception, so one suggestion of how this can be addressed is by having a call such as hdfsGetLastException() that would return the last exception that a libHDFS thread encountered. This way, an application may choose to call hdfsGetLastException() if it receives EINTERNAL.
> We can make use of the Thread Local Storage to store this information. Also, this makes sure that the current functionality is preserved.
> This is a follow up from HDFS-4997.


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