[asterisk-users] Simplest way of executing a non-blocking (async) python AGI script?

[Jonathan H]

Oh wow - thank you SO much Marcelo.

This works perfectly - exactly as I wanted. Don't think I'd have
figured it out, though.

Well, that ticket says "not a bug" if this isn't a bug, then
"behaviour which differs dramatically from that which is expected"
would definitely be the tag.

Again, this fix works, and thank you!



On 30 June 2017 at 23:18, Marcelo Terres <mhterres at gmail.com> wrote:
> Take a look on that:
>
> https://issues.asterisk.org/jira/browse/ASTERISK-20532
>
> Regards,
> Marcelo H. Terres <mhterres at gmail.com>
> IM: mhterres at jabber.mundoopensource.com.br
> https://www.mundoopensource.com.br
> https://twitter.com/mhterres
> https://linkedin.com/in/marceloterres
>
>
> On 30 June 2017 at 22:23, Jonathan H <lardconcepts at gmail.com> wrote:
>> OK, I give up and come grovelling, "Fork" was suggested at 18:23, it's
>> now 22:20 and I have been through 4 different methods, all block with
>> a 2 second delay before returning to dialplan.
>>
>> Here are just some of the examples I have tried, as as per the
>> suggestions, I am closing all possible outputs in the forked process.
>>
>> https://docs.python.org/3.5/library/multiprocessing.html
>> https://docs.python.org/3.5/library/multiprocessing.html?highlight=multiprocessing#multiprocessing.Process.join
>> https://stackoverflow.com/questions/19747371/python-exit-commands-why-so-many-and-when-should-each-be-used
>> https://stackoverflow.com/questions/27624850/launch-a-completely-independent-process
>> https://stackoverflow.com/questions/13612434/why-are-the-methods-sys-exit-exit-raise-systemexit-not-working
>> https://stackoverflow.com/questions/43280947/os-fork-share-local-variable-with-parent
>> https://stackoverflow.com/questions/24052217/may-someone-explain-the-following-os-fork-example-to-me
>> http://www.python-course.eu/forking.php
>> https://pymotw.com/3/subprocess/
>> http://code.activestate.com/recipes/186101-really-closing-stdin-stdout-stderr/
>>
>> This is the most likely looking code based on the examples. I would
>> really, really appreciate a couple of pointers as to where I might be
>> going wrong:
>>
>> #! /usr/bin/env python3
>> # -*- coding: utf-8 -*-
>>
>> import multiprocessing as mp
>> import time
>> import sys
>> import os
>>
>> #from asterisk.agi import AGI
>> #agi = AGI()
>>
>> def f(name):
>>     sys.stdin.close()
>>     sys.stdout.close()
>>     sys.stderr.close()
>>     os.close(0)   # close C's stdin stream
>>     os.close(1)   # close C's stdout stream
>>     os.close(2)   # close C's stderr stream
>>     time.sleep(2)
>>     f = open('/var/lib/asterisk/agi-bin/tns/testing/testout.txt', 'w')
>>     f.write(name)
>>     f.close()
>>
>>
>> if __name__ == '__main__':
>>     print('before process')
>>     mp.set_start_method('fork')
>>     q = mp.Queue()
>>     p = mp.Process(target=f, args=('asterisk',))
>>     p.start()
>>     sys.exit()
>>
>> On 30 June 2017 at 19:59, J Montoya or A J Stiles
>> <asterisk_list at earthshod.co.uk> wrote:
>>> On Friday 30 Jun 2017, Jonathan H wrote:
>>>> What's the simplest, easiest quickest least-code way of firing off an AGI
>>>> with some variable, and then returning to the dialplan?
>>>
>>> You have to use the "fork" command.  This starts a copy of the process with
>>> all the same internal state including variables and filehandles.  The command
>>> returns a non-zero value  (which is the PID of the child process; you may need
>>> this, if you plan to outlive your children and have to clear their entries
>>> from the process table)  to the parent process, and zero to the child process.
>>> So in the parent, you exit and return to the dialplan; and in the child, you
>>> close STDIN, STDOUT and STDERR  (so no process is waiting for you to produce
>>> output),  then just take your time doing what you have to.  The parent is
>>> already long dead by this time, so exiting goes nowhere.
>>>
>>>> I've seen people talking about fastAGI, stasis, python ASYNC... all seems
>>>> rather complicated. I feel I must be missing something embarrassingly
>>>> obvious - isn't there just the equivalent of the unix shell's "&"?!
>>>
>>> Yes, fork!  That is what the "&" operator is using "under the bonnet".
>>>
>>> --
>>> JKLM
>>>
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>>> list, change address to asterisk1list at earthshod dot co dot uk .
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