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Date: Thu, 23 Jun 2011 23:22:47 +0000 (UTC)
From: "Eli Collins (JIRA)" <jira@apache.org>
To: common-dev@hadoop.apache.org
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Subject: [jira] [Created] (HADOOP-7424) Log an error if the topology script
 doesn't handle multiple args
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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


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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