TaskLogsTruncater does not need to check log ownership when running as Child
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Key: MAPREDUCE-2371
URL: https://issues.apache.org/jira/browse/MAPREDUCE-2371
Project: Hadoop Map/Reduce
Issue Type: Improvement
Affects Versions: 0.23.0
Reporter: Todd Lipcon
Assignee: Todd Lipcon
Fix For: 0.23.0
Before MAPREDUCE-2178, it used to be that the TaskLogsTruncater had to use the
SecureIO API to open the task logs before truncation, to avoid an attack where
the user would symlink in something that the TT had access to but not the user.
After MAPREDUCE-2178, this truncation is done as the user rather than as the
TT, so we don't need to perform this check.
Not performing the check avoids a fork() call which we've found to be
troublesome since it doubles vmem consumption and thus requires that users bump
mapred.child.ulimit to >2x the expected child heap size.
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