[jira] [Updated] (HADOOP-7424) Log an error if the topology script doesn't handle multiple args

["Uma Maheswara Rao G (Updated) (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-7424?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Uma Maheswara Rao G updated HADOOP-7424:
----------------------------------------

    Attachment: HADOOP-7424.patch

Small patch as per the Eli suggestions and cleaned some of the unused imports.
                
> Log an error if the topology script doesn't handle multiple args
> ----------------------------------------------------------------
>
>                 Key: HADOOP-7424
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7424
>             Project: Hadoop Common
>          Issue Type: Improvement
>            Reporter: Eli Collins
>              Labels: newbie
>         Attachments: HADOOP-7424.patch
>
>
> ScriptBasedMapping#resolve currently warns and returns null if it passes n arguments to the topology script and gets back a different number of resolutions. This indicates a bug in the topology script (or it's input) and therefore should be an error.
> {code}
> // invalid number of entries returned by the script
> LOG.warn("Script " + scriptName + " returned "
>    + Integer.toString(m.size()) + " values when "
>    + Integer.toString(names.size()) + " were expected.");
> return null;
> {code}
> There's only one place in Hadoop (FSNamesystem init) where we pass multiple arguments to the topology script, and it only done for performance (to trigger resolution/caching of all the hosts in the includes file on startup). So currently a topology script that doesn't handle multiple arguments just means the initial cache population doesn't work.

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