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

[Jonathan H]

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
>
> Note:  Originating address only accepts e-mail from list!  If replying off-
> list, change address to asterisk1list at earthshod dot co dot uk .
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