Django command with lockfile

locked_command.py

import logging
from os.path import exists
from os import remove, getpid

from django.core.management.base import BaseCommand

logger = logging.getLogger(__name__)

class LockedCommand(BaseCommand):
    """
    A base class for Django commands that shouldn't run concurrently.
    Your command should inherit from LockedCommand and implement a locked_handle method.
    """

    def add_arguments(self, parser):
        parser.add_argument('lockfile')

    def handle(self, *args, **options):
        pid = str(getpid())
        logger.debug('Starting with pid %s' % pid)
        lockfile = options['lockfile']
        if exists(lockfile):
            with open(lockfile, 'r') as fin:
                oldpid = fin.read().strip()
            logger.debug('Lock file %s exists for PID %s, exiting!' % (lockfile, oldpid))
            return
        with open(lockfile, 'w') as fout:
            fout.write(pid)
        try:
            self.locked_handle(*args, **options)
        except Exception:
            logger.exception('Unexpected error in locked command')
        finally:
            if exists(lockfile):
                remove(lockfile)