Celery auto reload on ANY changes

Question

I could make celery reload itself automatically when there is changes on modules in CELERY_IMPORTS in settings.py.

I tried to give mother modules to detect changes even on child modules but it did not detect changes in child modules. That make me understand that detecting is not done recursively by celery. I searched it in the documentation but I did not meet any response for my problem.

It is really bothering me to add everything related celery part of my project to CELERY_IMPORTS to detect changes.

Is there a way to tell celery that "auto reload yourself when there is any changes in anywhere of project".

Thank You!

Answer 1

You can manually include additional modules with -I|--include. Combine this with GNU tools like find and awk and you'll be able to find all .py files and include them.

$ celery -A app worker --autoreload --include=$(find . -name "*.py" -type f | awk '{sub("\./",""); gsub("/", "."); sub(".py",""); print}' ORS=',' | sed 's/.$//')

Lets explain it:

find . -name "*.py" -type f

find searches recursively for all files containing .py. The output looks something like this:

./app.py
./some_package/foopy
./some_package/bar.py

Then:

awk '{sub("\./",""); gsub("/", "."); sub(".py",""); print}' ORS=','

This line takes output of find as input and removes all occurences of ./. Then it replaces all / with a .. The last sub() removes replaces .py with an empty string. ORS replaces all newlines with ,. This outputs:

app,some_package.foo,some_package.bar,

The last command, sed removes the last ,.

So the command that is being executed looks like:

$ celery -A app worker --autoreload --include=app,some_package.foo,some_package.bar

If you have a virtualenv inside your source you can exclude it by adding -path .path_to_your_env -prune -o:

$ celery -A app worker --autoreload --include=$(find . -path .path_to_your_env -prune -o -name "*.py" -type f | awk '{sub("\./",""); gsub("/", "."); sub(".py",""); print}' ORS=',' | sed 's/.$//')

Answer 2

Celery --autoreload doesn't work and it is deprecated.

Since you are using django, you can write a management command for that. Django has autoreload utility which is used by runserver to restart WSGI server when code changes.

The same functionality can be used to reload celery workers. Create a seperate management command called celery. Write a function to kill existing worker and start a new worker. Now hook this function to autoreload as follows.

import shlex
import subprocess

from django.core.management.base import BaseCommand
from django.utils import autoreload


def restart_celery():
    cmd = 'pkill celery'
    subprocess.call(shlex.split(cmd))
    cmd = 'celery worker -l info -A foo'
    subprocess.call(shlex.split(cmd))


class Command(BaseCommand):

    def handle(self, *args, **options):
        print('Starting celery worker with autoreload...')

        # For Django>=2.2
        autoreload.run_with_reloader(restart_celery) 

        # For django<2.1
        # autoreload.main(restart_celery)

Now you can run celery worker with python manage.py celery which will autoreload when codebase changes.

This is only for development purposes and do not use it in production. Code taken from my other answer here.

Answer 3

You can use watchmedo

pip install watchdog

Start celery worker indirectly via watchmedo

watchmedo auto-restart --directory=./ --pattern=*.py --recursive -- celery worker --app=worker.app --concurrency=1 --loglevel=INFO

More detailed

Answer 4

I used watchdog watchdemo utility, it works great but for some reason the PyCharm debugger was not able to debug the subprocess spawned by watchdemo.

So if your project has werkzeug as dependency, you can use the werkzeug._reloader.run_with_reloader function to autoreload celery worker on code change. Plus it works with PyCharm debugger.

"""
Filename: celery_dev.py
"""

import sys

from werkzeug._reloader import run_with_reloader

# this is the celery app path in my application, change it according to your project
from web.app import celery_app


def run():
    # create copy of "argv" and remove script name
    argv = sys.argv.copy()
    argv.pop(0)

    # start the celery worker
    celery_app.worker_main(argv)


if __name__ == '__main__':
    run_with_reloader(run)

Sample PyCharm debug configuration.

NOTE:

This is a private werkzeug API and is working as of Werkzeug==2.0.3. It may stop working in future versions. Use at you own risk.

Answer 5

OrangeTux's solution didn't work out for me, so I wrote a little Python script to achieve more or less the same. It monitors file changes using inotify, and triggers a celery restart if it detects a IN_MODIFY, IN_ATTRIB, or IN_DELETE.

#!/usr/bin/env python
"""Runs a celery worker, and reloads on a file change. Run as ./run_celery [directory]. If
directory is not given, default to cwd."""
import os
import sys
import signal
import time

import multiprocessing
import subprocess
import threading

import inotify.adapters


CELERY_CMD = tuple("celery -A amcat.amcatcelery worker -l info -Q amcat".split())
CHANGE_EVENTS = ("IN_MODIFY", "IN_ATTRIB", "IN_DELETE")
WATCH_EXTENSIONS = (".py",)

def watch_tree(stop, path, event):
    """
    @type stop: multiprocessing.Event
    @type event: multiprocessing.Event
    """
    path = os.path.abspath(path)

    for e in inotify.adapters.InotifyTree(path).event_gen():
        if stop.is_set():
            break

        if e is not None:
            _, attrs, path, filename = e

            if filename is None:
                continue

            if any(filename.endswith(ename) for ename in WATCH_EXTENSIONS):
                continue

            if any(ename in attrs for ename in CHANGE_EVENTS):
                event.set()


class Watcher(threading.Thread):
    def __init__(self, path):
        super(Watcher, self).__init__()
        self.celery = subprocess.Popen(CELERY_CMD)
        self.stop_event_wtree = multiprocessing.Event()
        self.event_triggered_wtree = multiprocessing.Event()
        self.wtree = multiprocessing.Process(target=watch_tree, args=(self.stop_event_wtree, path, self.event_triggered_wtree))
        self.wtree.start()
        self.running = True

    def run(self):
        while self.running:
            if self.event_triggered_wtree.is_set():
                self.event_triggered_wtree.clear()
                self.restart_celery()
            time.sleep(1)

    def join(self, timeout=None):
        self.running = False
        self.stop_event_wtree.set()
        self.celery.terminate()
        self.wtree.join()
        self.celery.wait()
        super(Watcher, self).join(timeout=timeout)

    def restart_celery(self):
        self.celery.terminate()
        self.celery.wait()
        self.celery = subprocess.Popen(CELERY_CMD)


if __name__ == '__main__':
    watcher = Watcher(sys.argv[1] if len(sys.argv) > 1 else ".")
    watcher.start()

    signal.signal(signal.SIGINT, lambda signal, frame: watcher.join())
    signal.pause()

You should probably change CELERY_CMD, or any other global variables.

Answer 6

This is the way I made it work in Django:

# worker_dev.py (put it next to manage.py)
from django.utils import autoreload


def run_celery():
    from projectname import celery_app

    celery_app.worker_main(["-Aprojectname", "-linfo", "-Psolo"])


print("Starting celery worker with autoreload...")
autoreload.run_with_reloader(run_celery)

Then run python worker_dev.py. This has an advantage of working inside docker container.