Improvements to Global Black-listing of TaskTrackers
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Key: HADOOP-6014
URL: https://issues.apache.org/jira/browse/HADOOP-6014
Project: Hadoop Core
Issue Type: Improvement
Components: mapred
Affects Versions: 0.20.0
Reporter: Arun C Murthy
Fix For: 0.21.0
HADOOP-4305 added a global black-list of tasktrackers.
We saw a scenario on one of our clusters where a few jobs caused a lot of
tasktrackers to immediately be blacklisted. This was caused by a specific set
of jobs which (same user) whose tasks were shot down the by the TaskTracker for
being over the vmem limit of 2G. Each of these jobs had over 600 failures of
the same kind. This resulted in each of the users black-listing some
tasktrackers, which in itself is wrong since the failures had nothing to do
with the node on which the failure occurred (i.e. high memory usage) and
shouldn't have had to penalized the tasktracker. We clearly need to start
treating system and user failures separately for black-listing etc. A DiskError
is fatal and should probably we blacklisted immediately while a task which was
'failed' for using more memory shouldn't count against the tasktracker at all!
The other problem is that we never configured mapred.max.tracker.blacklists and
continue to use the default value of 4. Further more this config should really
be a percent of the cluster-size and not a whole number.
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