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From Benjamin Mahler <benjamin.mah...@gmail.com>
Subject Re: OOM not always detected by Mesos Slave
Date Sat, 13 Sep 2014 01:12:05 GMT
+Ian

Sorry for the delay, when your cgroup OOMs a few things will occur:

(1) The kernel will notify mesos-slave about the OOM event.
(2) The kernel's OOM killer will pick a process in your cgroup to kill.
(3) Once notified, mesos-slave will begin destroying the cgroup.
(4) Once the executor terminates, any tasks that were non-terminal on the
executor will have status updates sent with the OOM message.

This does not all happen atomically, so it is possible that the kernel
kills your task process and your executor sends a status update before the
slave completes the destruction of the cgroup.

Userspace OOM handling is supported, and we tried using it in the past, but
it is not reliable:

https://issues.apache.org/jira/browse/MESOS-662
http://lwn.net/Articles/317814/
http://lwn.net/Articles/552789/
http://lwn.net/Articles/590960/
http://lwn.net/Articles/591990/

Since you have the luxury of avoiding the OOM killer (JVM flags w/
padding), I would recommend leveraging that for now.

Do you have the logs for your issue? My guess is that it took time for us
to destroy the cgroup (possibly due to freezer issues) and so there was
plenty of time for your executor to send the status update to the slave.

On Sat, Sep 6, 2014 at 6:56 AM, Whitney Sorenson <wsorenson@hubspot.com>
wrote:

> We already pad the JVM and make room for our executor, and we try to get
> users to give the correct allowances.
>
> However, to be fair, your answer to my question about how Mesos is
> handling OOMs is to suggest we avoid them. I think we're always going to
> experience some cgroup OOMs and if we'd be better off if we had a
> consistent way of handling them.
>
>
> On Fri, Sep 5, 2014 at 3:20 PM, Tomas Barton <barton.tomas@gmail.com>
> wrote:
>
>> There is some overhead for the JVM itself, which should be added to the
>> total usage of memory for the task. So you can't have the same amount of
>> memory for the task as you pass to java, -Xmx parameter.
>>
>>
>> On 2 September 2014 20:43, Benjamin Mahler <benjamin.mahler@gmail.com>
>> wrote:
>>
>>> Looks like you're using the JVM, can you set all of your JVM flags to
>>> limit the memory consumption? This would favor an OutOfMemoryError instead
>>> of OOMing the cgroup.
>>>
>>>
>>> On Thu, Aug 28, 2014 at 5:51 AM, Whitney Sorenson <wsorenson@hubspot.com
>>> > wrote:
>>>
>>>> Recently, I've seen at least one case where a process inside of a task
>>>> inside of a cgroup exceeded memory limits and the process was killed
>>>> directly. The executor recognized the process was killed and sent a
>>>> TASK_FAILED. However, it seems far more common to see the executor process
>>>> itself destroyed and the mesos slave (I'm making some assumptions here
>>>> about how it all works) sends a TASK_FAILED which includes information
>>>> about the memory usage.
>>>>
>>>> Is there something we can do to make this behavior more consistent?
>>>>
>>>> Alternatively, can we provide some functionality to hook into so we
>>>> don't need to duplicate the work of the mesos slave in order to provide the
>>>> same information in the TASK_FAILED message? I think users would like to
>>>> know definitively that the task OOM'd, whereas in the case where the
>>>> underlying task is killed it may take a lot of digging to find the
>>>> underlying cause if you aren't looking for it.
>>>>
>>>> -Whitney
>>>>
>>>> Here are relevant lines from messages in case something else is amiss:
>>>>
>>>> Aug 27 23:24:07 ip-10-237-165-119 kernel: [2604343.067321] Task in
>>>> /mesos/2dda5398-6aa6-49bb-8904-37548eae837e killed as a result of limit of
>>>> /mesos/2dda5398-6aa6-49bb-8904-37548eae837e
>>>> Aug 27 23:24:07 ip-10-237-165-119 kernel: [2604343.067334] memory:
>>>> usage 917420kB, limit 917504kB, failcnt 106672
>>>> Aug 27 23:24:07 ip-10-237-165-119 kernel: [2604343.066947] java7
>>>> invoked oom-killer: gfp_mask=0xd0, order=0, oom_adj=0, oom_score_adj=0
>>>>
>>>>
>>>>
>>>>
>>>
>>
>

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