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From Stephan Erb <s...@apache.org>
Subject Re: Review Request 53403: [WIP] [DO NOT MERGE] Reparent orphaned processes to thermos runner and send SIGTERM on task teardown
Date Wed, 02 Nov 2016 22:41:03 GMT


> On Nov. 2, 2016, 10:23 p.m., Stephan Erb wrote:
> > src/main/python/apache/thermos/core/runner.py, lines 876-881
> > <https://reviews.apache.org/r/53403/diff/1/?file=1551918#file1551918line876>
> >
> >     The `TaskRunnerHelper.terminate_process` might generate new orphans. The call
to `terminate_orphans` should thus be placed after the loop.
> 
> Zameer Manji wrote:
>     I'm not sure if the this is the right thing to do.
>     
>     IMHO, it is a bug if a processes that has children gets SIGTERM and doesn't forward
that on. The children then deserve to die unexpectedly.
>     
>     I don't feel to strongly about this, but it is something to consider.

Good point. I am ok with keeping it the way it is then.


- Stephan


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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/53403/#review154633
-----------------------------------------------------------


On Nov. 2, 2016, 11:16 p.m., Zameer Manji wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/53403/
> -----------------------------------------------------------
> 
> (Updated Nov. 2, 2016, 11:16 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
> -------
> 
> 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
> 
>


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