[GRASS-dev] pygrass: How to allow Ctrl-C to stop all subprocesses of GridModule

[Nikos Alexandris]

* Moritz Lennert <mlennert at club.worldonline.be> [2018-03-09 09:16:01 +0100]:

>Hi Nikos !
>
>Am 9. März 2018 09:01:25 MEZ schrieb Nikos Alexandris <nik at nikosalexandris.net>:
>>* Moritz Lennert <mlennert at club.worldonline.be> [2018-03-08 15:05:46
>>+0100]:
>>
>>>And another question on GridModule:
>>>
>>>For the same module using GridModule to split the task of edge
>>>detection in a raster map into many parallel tasks, when I want to
>>>stop the module run using Ctrl-C I get tons of
>>>
>>>Process PoolWorker-315:
>>>Traceback (most recent call last):
>>>Traceback (most recent call last):
>>>  File "/usr/lib/python2.7/multiprocessing/process.py", line 267, in
>>>_bootstrap
>>>  File "/usr/lib/python2.7/multiprocessing/process.py", line 267, in
>>>_bootstrap
>>>    self.run()
>>>    self.run()
>>>  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in
>>run
>>>  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in
>>run
>>>    self._target(*self._args, **self._kwargs)
>>>    self._target(*self._args, **self._kwargs)
>>>  File "/usr/lib/python2.7/multiprocessing/pool.py", line 102, in
>>worker
>>>  File "/usr/lib/python2.7/multiprocessing/pool.py", line 102, in
>>worker
>>>    task = get()
>>>  File "/usr/lib/python2.7/multiprocessing/queues.py", line 374, in
>>get
>>>    task = get()
>>>  File "/usr/lib/python2.7/multiprocessing/queues.py", line 374, in
>>get
>>>    racquire()
>>>    racquire()
>>>KeyboardInterrupt
>>>
>>>
>>>and cannot stop the module, even when flooding the input with Ctrl-Cs.
>>>
>>>Any hint how to allow Ctrl-C to stop all subprocesses ?
>>>
>>>Moritz
>>
>>Moritz, could it be a case related to the ones mentioned in
>>
>>https://stackoverflow.com/a/1635084/1172302
>>https://stackoverflow.com/a/11816038/1172302
>
>
>
>Related yes, but AFAIU GridModule uses multiprocessing, not multithreading. I think it should be possible to modify something in the GridModule class so that it interrupts, but not sure about what exactly (apparently this is specifically a problem in Python 2. In Python 3 it should happen automatically IIUC.

Right. This https://stackoverflow.com/a/35134329/1172302 should be,
however, directly related. However, not portable, as per a comment.

How about this one: https://stackoverflow.com/a/44869451/1172302 (July
2017)? See
also
http://jessenoller.com/blog/2009/01/08/multiprocessingpool-and-keyboardinterrupt.

Nikos
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