[Problem] Not starting a new process with runner.run() ?

[twardoch]

I can run this code:

#!/usr/bin/env python3
from fontbakery.checkrunner import CheckRunner, get_module_profile
from fontbakery.commands.check_profile import get_module
from fontbakery.configuration import Configuration
from fontbakery.multiproc import multiprocessing_runner
from fontbakery.reporters.html import HTMLReporter
from fontbakery.status import WARN


def get_fontbakery_html(font_paths, profile_name="universal"):
    profile = get_module_profile(get_module(f"fontbakery.profiles.{profile_name}"))
    config = Configuration(full_lists=True)
    runner = CheckRunner(profile, values={"fonts": font_paths}, config=config)
    hr = HTMLReporter(runner=runner, loglevels=[WARN])
    hr_callback = hr.receive
    gen = runner.run()
    for item in gen:
        hr_callback(item)
    return hr.get_html()


def main(font_path, profile_name="universal"):
    return get_fontbakery_html([font_path], profile_name)


print(main("/Users/adam/Desktop/Nabla/Web-TT/Nabla-Regular-COLRv1.ttf"))

in Terminal, and it works just fine.

But when I run the same code in FontLab 8, FontLab runs another instance of FontLab in the line that has runner.run(), and then waits infinitely until I quit the other instance of FontLab. This is because FontLab 8 is the "interpreter" executable for FontLab scripts, and generally this happens if I start a new process from Python.

This indicates that somewhere in the code, FontBakery is running another instance (process) of the Python interpreter.

1. Where can this happen?
2. How do I prevent this?

[twardoch]

I understand where this happens if I use multiprocessing_runner but I don’t quite understand how a new process gets spun off if I just use runner.run().

[davelab6]

@graphicore might have some insight

[graphicore]

I have no good idea what's causing this. All the multi-processing done by multiprocessing_runner is in the multiproc module. It shouldn't do these things if you don't call that code.

But maybe some check creates a sub-process? You could try to run with less checks, or maybe with just one check at a time and see if some checks run and some checks block.
For debugging, can you identify the child processes created by FontLab? How do they get called? When I run e.g. $ fontbakery check-googlefonts -j ./fonts/ofl/rubik/* and monitor it using the htop command (with f4 FILTER: fontbakery), I see all the sub processes called with the same command, but sometimes a call to $ /home/commander/Projects/googlefonts/fontbakery/venv/bin/python3 -m pip list -v --format=json pops up. I think that might come from com.google.fonts/check/fontbakery_version in profiles/universal.py, Same subprocess also without multiprocessing/-j.

[graphicore]

If you can use TerminalReporter set print_progress=false and maybe set stdout to a python file-like that writes to a file, you should get a progress report until the blocking position, including the last output for STARTCHECK which happens before the check itself is executed.

[graphicore]

cc @twardoch @davelab6: direct mentioning you as I don't know if the discussions feature would inform you when I post in a sub-thread. Also, should this be an issue?