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From "Arun C Murthy (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-1278) Fix the per-job tasktracker 'blacklist'
Date Fri, 20 Apr 2007 06:34:15 GMT
Fix the per-job tasktracker 'blacklist'
---------------------------------------

                 Key: HADOOP-1278
                 URL: https://issues.apache.org/jira/browse/HADOOP-1278
             Project: Hadoop
          Issue Type: Bug
          Components: mapred
            Reporter: Arun C Murthy
         Assigned To: Arun C Murthy
             Fix For: 0.13.0


Today whenever a tracker is 'lost' all the jobs which ever ran on it are considered as failures
and added to the blacklist, which automatically ensures that the particular TT is *never*
considered for allocating new tasks unless *all* tasktrackers are on the list. This results
in an ugly situation where a majority of nodes in the cluster are on the blacklist and hence
idle, while the other TTs are maxed out.

The proposal is two-fold:
a) Don't count *all* tasks which ever ran on the TT, we can count it as a 'single' task failure
- which means that each 'lost' tracker results in a loss of 20% of the '5 failures == blacklisted'
 quota.
b) Stop adding nodes to the blacklist when a certain percentage of the cluster, say 25%, are
already on the blacklist - adding more than that would just delay the inevitable i.e. there
is something horrendously wrong with the cluster - we might as well fail the job early and
noisily.

Thoughts?

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