How to lock a critical section in Django?

Question

I can\'t find a good clean way to lock a critical section in Django. I could use a lock or semaphore but the python implementation is for threads only, so if the production

Answer 1

I ended up going with a solution I made myself involving file locking. If anyone here ends up using it remember that advisory locks and NFS don't mix well, so keep it local. Also, this is a blocking lock, if you want to mess around with loops and constantly checking back then there is instructions in the code.

import os
import fcntl

class DjangoLock:

    def __init__(self, filename):
        self.filename = filename
        # This will create it if it does not exist already
        self.handle = open(filename, 'w')

    # flock() is a blocking call unless it is bitwise ORed with LOCK_NB to avoid blocking 
    # on lock acquisition.  This blocking is what I use to provide atomicity across forked
    # Django processes since native python locks and semaphores only work at the thread level
    def acquire(self):
        fcntl.flock(self.handle, fcntl.LOCK_EX)

    def release(self):
        fcntl.flock(self.handle, fcntl.LOCK_UN)

    def __del__(self):
        self.handle.close()

Usage:

lock = DJangoLock('/tmp/djangolock.tmp')
lock.acquire()
try:
    pass
finally:
    lock.release()