How do I make a decorator for Django management command processing locking?

Question

I have a Django project that has many custom management commands that get executed from crontab. I need to implement locking in these commands to prevent cron from starting multiple instances of the command executions. So I am going through each of my custom management commands and changing:

    def handle(self, *args, **options):
        ...

to:

from lockmgr.lockmgr import LockMgr, Locked

...

    def run_handle(self, *args, **options):
        ''' I renamed handle() to run_handle(). '''
        ...


    def handle(self, *args, **options):

        command = sys.argv[1]
        try:
            with LockMgr(f'{command}_lock') as l:
                self.run_handle(*args, **options)

        except Locked as e:
            errmsg = f'{command} failed to lock. Reason: {e}.'
            self.stdout.write(errmsg)
            self.logger.error(errmsg)

Then I started thinking that I should probably use a "decorator" here, but I am not quite sure how to do that. Any help would be great.

Thanks.

Answer 1

Ah figured it out. I need to create a python file ...

myproject/decorators/lock_cron_job.py

from lockmgr.lockmgr import LockMgr, Locked
import logging
import sys


def lock_cron_job():
    """Decorator that uses LockMgr."""
    def decorator(handle_func):
        def wrapped(*args, **kwargs):
            command = sys.argv[1]
            log = logging.getLogger(command)
            try:
                with LockMgr(f'{command}_lock'):
                    handle_func(*args, **kwargs)
            except Locked as e:
                errmsg = f'{command} failed to lock. Reason: {e}'
                log.error(errmsg)
        return wrapped
    return decorator

and then in my custom management commands I would do this:

from myproject.decorators.lock_cron_job import lock_cron_job

...


    @lock_cron_job()
    def handle(self, *args, **options):
        ...