Sharing a lock between gunicorn workers

Question

Is there a good way to share a multiprocessing Lock between gunicorn workers? I am trying to write a json API with Flask. Some of the API calls will interact a python class that manages a running process (like ffmpeg for video conversion). When I scale up my number of web workers to more than 1, how can I ensure that only 1 worker is interacting with the class at the same time? My initial thought was to use multiprocessing.Lock so the start() function can be atomic. I don't think I've figured out the right place to create a Lock so that one is shared across all the workers: ``` # runserver.py from flask import Flask from werkzeug.contrib.fixers import ProxyFix import dummy app = Flask(__name__) @app.route('/') def hello(): dummy.start() return "ffmpeg started" app.wsgi_app = ProxyFix(app.wsgi_app) if __name__ == '__main__': app.run() ``` Here is my dummy operation: ``` # dummy.py from multiprocessing import Lock import time lock = Lock() def start(): lock.acquire() # TODO do work for…

Accepted Answer

Follow peterw's answer, the workers can share the lock resource.

But, It is better to use `try-finally` block to ensure the lock will always be released.

```
# dummy.py
from multiprocessing import Lock
import time

lock = Lock()

def start():
    lock.acquire()

try:
        # TODO do work
        for i in range(0,10):
            print "did work %s" % i
            time.sleep(1)
    finally:
        lock.release()
```

Sharing a lock between gunicorn workers

Solution

Problem