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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

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
> 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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