Review Request 55778: Moved check for 'has_parent()' in docker containerizer destroy.

[Kevin Klues <kl...@gmail.com>]

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Review request for mesos, Benjamin Mahler and Jie Yu.


Bugs: MESOS-6214 and MESOS-6954
    https://issues.apache.org/jira/browse/MESOS-6214
    https://issues.apache.org/jira/browse/MESOS-6954


Repository: mesos


Description
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Ideally, we would do this check as the first thing we do after
entering this function. However, the containerizer API currently
requires callers of `launch()` to also call `destroy()` if the launch
fails (MESOS-6214). As such, putting the check at the top of this
function would cause the containerizer to crash if the launch failure
was due to the container having its `parent` field set. Once we remove
the requirement for `destroy()` to be called explicitly after launch
failures, we should move this check back to the top of this function.


Diffs
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  src/slave/containerizer/docker.cpp cfc67951dc29e4ed804614aeb36b76cf7d499add 

Diff: https://reviews.apache.org/r/55778/diff/


Testing
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GTEST_FILTER="" make -j check
sudo src/mesos-tests


Thanks,

Kevin Klues