[slurm-users] Drain node from TaskProlog / TaskEpilog

Brian Andrus toomuchit at gmail.com
Mon May 24 16:59:40 UTC 2021

Ah. I'll proceed under the scenario that there is a piece of hardware 
that is being tested and may lock up (The GPU in this case).

If you are able to identify the issue is occurring from within the job, 
you should exit the job with an error or some signal to alert slurm (eg: 
a semaphore file). You can then use something like EpilogSlurmctld to 
recognize that and reboot the node accordingly.

This is presuming the node needs a full reboot, which I am guessing 
affects the entire job. If you are able to do something like 
unload/reload the cuda drivers between tasks, that may be a way to 
continue the job while still 'fixing' the issue. That could be done in 
the TaskEpilog script (assuming your daemon user has permissions to do so).

On 5/24/2021 8:56 AM, Mark Dixon wrote:
> Hi Brian,
> Thanks for replying. On our hardware, GPUs allocated to a job by 
> cgroup sometimes get themselves into a state requiring a reboot.
> Outside the job, a simple CUDA program calling the API function 
> cudaGetDeviceCount works happily. Inside the job, it returns an error 
> code of 3 (cudaErrorInitializationError).
> At present, I have a TaskProlog that prods this API function and 
> emails me when there is a failure. It'd be nice if the nodes could 
> drain themselves without administrator intervention, rather than 
> continuing to run waiting jobs and so causing them to fail.
> I can see a couple of ways to do it (e.g. sudo script in TaskProlog, 
> or playing with the cgroup hierarchy outside of slurm), but was 
> wondering if I had misunderstood the slurm docs and there was a 
> simpler way.
> Best,
> Mark
> On Mon, 24 May 2021, Brian Andrus wrote:
>> Not sure I can understand how it can only be detected from inside the
>> job environment for a failed node.
>> That description is more of "our application is behaving badly, but not
>> so bad, the node quits responding." For that situation, your app or job
>> should have something that it is doing to catch that and report it to
>> slurm in some fashion (up to and including, kill the process).
>> Slurm polls the nodes and if slurmd does not respond, it will mark the
>> node as failed. So slurmd must be responding.
>> If you can provide a better description of what symptoms you see that
>> cause you to feel the node has failed, we can help a little more.
>> On 5/24/2021 3:02 AM, Mark Dixon wrote:
>>>  Hi all,
>>>  Sometimes our compute nodes get into a failed state which we can only
>>>  detect from inside the job environment.
>>>  I can see that TaskProlog / TaskEpilog allows us to run our detection
>>>  test; however, unlike Epilog and Prolog, they do not drain a node if
>>>  they exit with a non-zero exit code.
>>>  Does anyone have advice on automatically draining a node in this
>>>  situation, please?
>>>  Best wishes,
>>>  Mark

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