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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/53403/
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(Updated Nov. 2, 2016, 1:32 p.m.)
Review request for Aurora, Joshua Cohen, Santhosh Kumar Shanmugham, and Stephan
Erb.
Bugs: AURORA-1808
https://issues.apache.org/jira/browse/AURORA-1808
Repository: aurora
Description (updated)
-------
This is a WIP patch showing a possible fix to AURORA-1808.
# Problem
Processes can deamonize and escape the supervision of a coordinator. Using the
Docker Containerizer or the Mesos Containerizer with pid isolation means that
the processes will be come reparented to the `sh` process that launches the
executor. For example:
````
root@aurora:/# ps xf
PID TTY STAT TIME COMMAND
48 ? Ss 0:00 /bin/bash
86 ? R+ 0:00 _ ps xf
1 ? Ss 0:00 /bin/sh -c ${MESOS_SANDBOX=.}/thermos_executor.pex
--announcer-ensemble localhost:2181 --announcer-zookeeper-auth-config
/home/vagrant/aurora/examples/va
5 ? Sl 0:02 python2.7 /mnt/mesos/sandbox/thermos_executor.pex
--announcer-ensemble localhost:2181 --announcer-zookeeper-auth-config
/home/vagrant/aurora/examples/vag
23 ? S 0:00 _ /usr/local/bin/python2.7
/mnt/mesos/sandbox/thermos_runner.pex
--task_id=www-data-devel-hello_docker_engine-0-bde5cdc7-8685-46fd-9078-4a86bd5be152
--
29 ? Ss 0:00 _ /usr/local/bin/python2.7
/mnt/mesos/sandbox/thermos_runner.pex
--task_id=www-data-devel-hello_docker_engine-0-bde5cdc7-8685-46fd-9078-4a86bd5be15
32 ? S 0:00 | _ /bin/bash -c while true; do
echo hello world sleep 10 done
81 ? S 0:00 | _ sleep 10
31 ? Ss 0:00 _ /usr/local/bin/python2.7
/mnt/mesos/sandbox/thermos_runner.pex
--task_id=www-data-devel-hello_docker_engine-0-bde5cdc7-8685-46fd-9078-4a86bd5be15
33 ? S 0:00 _ /bin/bash -c while true; do
echo hello world sleep 10 done
82 ? S 0:00 _ sleep 10
47 ? S 0:00 python ./daemon.py
````
# Solution
Ensure processes that escape the supervision of the coordinator reparent to the
runner who can send signals to them on task tear down. We do this by using the
`PR_SET_CHILD_SUBREAPER` flag of `prctl(2)`.
After this change the process tree looks like:
````
root@aurora:/# ps xf
PID TTY STAT TIME COMMAND
66 ? Ss 0:00 /bin/bash
70 ? R+ 0:00 _ ps xf
1 ? Ss 0:00 /bin/sh -c ${MESOS_SANDBOX=.}/thermos_executor.pex
--announcer-ensemble localhost:2181 --announcer-zookeeper-auth-config
/home/vagrant/aurora/examples/va
5 ? Sl 0:02 python2.7 /mnt/mesos/sandbox/thermos_executor.pex
--announcer-ensemble localhost:2181 --announcer-zookeeper-auth-config
/home/vagrant/aurora/examples/vag
23 ? S 0:00 _ /usr/local/bin/python2.7
/mnt/mesos/sandbox/thermos_runner.pex
--task_id=www-data-devel-hello_docker_engine-0-721406db-00f5-4c0c-915e-1dbc5568b849
--
33 ? Ss 0:00 _ /usr/local/bin/python2.7
/mnt/mesos/sandbox/thermos_runner.pex
--task_id=www-data-devel-hello_docker_engine-0-721406db-00f5-4c0c-915e-1dbc5568b84
40 ? S 0:00 | _ /bin/bash -c while true; do
echo hello world sleep 10 done
63 ? S 0:00 | _ sleep 10
36 ? Ss 0:00 _ /usr/local/bin/python2.7
/mnt/mesos/sandbox/thermos_runner.pex
--task_id=www-data-devel-hello_docker_engine-0-721406db-00f5-4c0c-915e-1dbc5568b84
37 ? S 0:00 | _ /bin/bash -c while true; do
echo hello world sleep 10 done
62 ? S 0:00 | _ sleep 10
55 ? S 0:00 _ python ./daemon.py
````
Now the runner is aware of the reparented procesess can can tear it down
cleanly during teardown.
Note that the man page for `prctl(2)` says that the processes that set
`PR_SET_CHILD_SUBREAPER` should reap children to get rid of zombies. It is
important to note tht the runner already does this in its run loop via
`TaskRunnerHelper.reap_children()`. This patch has the side effect of ensuring
it will reap all of the children launched via coordinators.
Diffs
-----
src/main/python/apache/thermos/common/process_util.py
abd2c0ef35858d13971319b0a7436ce2293824ce
src/main/python/apache/thermos/core/helper.py
68855e1e54ba1cd4456e18a36fb237ce6a468c34
src/main/python/apache/thermos/core/process.py
3ec43e2719ef97026f399c4b2aa23002559b3153
src/main/python/apache/thermos/core/runner.py
7b9013d11f6ff4172b6b7bf56e62299b0d11c977
Diff: https://reviews.apache.org/r/53403/diff/
Testing
-------
no automated tests yet.
Validated behaviour with `ps` and `strace`.
Thanks,
Zameer Manji
