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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] Created: (MAPREDUCE-2371) TaskLogsTruncater does not need to check log ownership when running as Child
Date Tue, 08 Mar 2011 21:00:59 GMT
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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