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From "Philip Zeyliger (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-890) Have a way of creating datanodes that throws an meaningful exception on failure
Date Mon, 11 Jan 2010 18:19:54 GMT

    [ https://issues.apache.org/jira/browse/HDFS-890?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12798759#action_12798759
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Philip Zeyliger commented on HDFS-890:
--------------------------------------

Do you need to mark the old API as deprecated?  Isn't the "documented" way of starting datanodes
"bin/hdfs datanode"?  If we can get away with it, fewer deprecated methods are better.

I'm +1 having real exit codes.

> Have a way of creating datanodes that throws an meaningful exception on failure
> -------------------------------------------------------------------------------
>
>                 Key: HDFS-890
>                 URL: https://issues.apache.org/jira/browse/HDFS-890
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: data-node
>    Affects Versions: 0.22.0
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>
> In HDFS-884, I proposed printing out more details on why things fail. This is hard to
test, because you need to subvert the log4j back end that your test harness will itself have
grabbed.
> There is a way to make it testable, and to make it easier for anyone creating datanodes
in process to recognise and handle failure: have a static CreateDatanode() method that throws
exceptions when directories cannot be created or other problems arise. Right now some problems
trigger failure, others just return a null reference saying "something went wrong but we won't
tell you what -hope you know where the logs go". 
> The HDFS-884 patch would be replaced by something that threw an exception; the existing
methods would catch this, log it and return null. The new method would pass it straight up.

> This is easier to test, better for others. If people think this is good, I will code
it up and mark the old API as deprecated. 

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