[py-dev] pytest-timeout 0.2

holger krekel holger at merlinux.eu
Tue Mar 20 07:10:12 CET 2012

Hi Laurent, Floris,

On Mon, Mar 19, 2012 at 16:47 -0700, Brack, Laurent P. wrote:
> I don't want to make this issue overly complicated but here are some scenarios (that we have).

proper termination and handling of hanging tests is involved.  So 
discussion and hearing use cases makes sense to me.

> Our tests, in some instances, interact with python extensions written in C or C++ (or in some case COM inproc server - yuk) which can be multi-threaded.
> If the hang occurs in a critical section in the C/C++ domain I am not sure what the timeout effect would be but 
> Assuming that the test is pre-empted in a critical section (of the extension), we would most likely be doomed anyway (mutexes would not be released). Next test would hang, be aborted and so on. 
> In our case, the safest thing to do is to run with xdist -n 1 so then the OS takes care of doing most if not all the cleanup.
> I am not so intimate with xdist but I was hoping that upon detecting that the "remote process" had died, 
> xdist would restart a new one. 

It's reasonable to expect this from the xdist plugin, even when you run with
"-n N" with N>1.

> In this case pytest ended with:
> [gw0] win32 -- Python 2.7.2 C:\Python27\python.exe
> Slave 'gw0' crashed while running 'src/timeout/test_sample.py::TestTimeOut::()::test_hang'
> Which signaled the end of everything (other tests were not run). This is a something we will have to solve internally 
> (and when we have the solution will be more than happy to contribute it back). We might be able to restart a remote 
> Process on pytest_testnodedown(). We would be however too late to run any restore() and chances are that those might hang as well.

Indeed, no attempt is made to restart a node properly. It remains offline
and when run with "-n1" everything dies because no node is left to continue.
Not sure how hard it is to try to fix it.

> More food for thoughts than anything at this point. 
> Floris, thanks for your work. We are not yet in a position where we can help much but we will get to it.

Coming to think of it, the xdist plugin might also do "timeout" handling
and send a keyboard interrupt from the outside to a running node.

> /Laurent
> P.S.: Speaking of xdist, further down the road we are interested in extending xdist (via its hooks) to interface it with OpenStack (dynamic provisioning of VM). Anyone has any use for this or thinking about the same thing?

I am interested in OpenStack but you can you detail a bit more of what
you want to achieve?


> -----Original Message-----
> From: floris.bruynooghe at gmail.com [mailto:floris.bruynooghe at gmail.com] On Behalf Of Floris Bruynooghe
> Sent: Monday, March 19, 2012 3:21 PM
> To: Brack, Laurent P.
> Cc: holger krekel; py-dev at codespeak.net; Brard, Valentin
> Subject: Re: [py-dev] pytest-timeout 0.2
> On 19 March 2012 16:38, Brack, Laurent P. <lpbrac at dolby.com> wrote:
> > It would also be nice to have a consistent behavior between sigalarm on/off. For instance, on Windows, pytest exits on first hang as opposed to *nix where the test is pre-empted and pytest moves on to the next one.
> I was writing up a response saying I didn't know how to do so, but while doing so I thought it might be possible to emulate sigalrm with a timer thread which fires an other signal.  I might investigate the feasibility of such an approach.  I do worry about gratuitously using signals however, the simple timer thread with os._exit() may always have to stay as the fail-safe option.
> If anyone has any other ideas about this please let me know.
> Regards,
> Floris
> --
> Debian GNU/Linux -- The Power of Freedom www.debian.org | www.gnu.org | www.kernel.org

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