dramatiq-crontab

Dramatiq Crontab

Cron style scheduler for asynchronous Dramatiq tasks in Django.

• setup recurring tasks via crontab syntax
• lightweight helpers build on robust tools like Dramatiq and APScheduler
• Sentry cron monitor support

Setup

You need to have Dramatiq installed and setup properly.

python3 -m pip install dramatiq-crontab
# or
python3 -m pip install dramatiq-crontab[sentry]  # with sentry cron monitor support

Add dramatiq_crontab to your INSTALLED_APPS in settings.py:

# settings.py
INSTALLED_APPS = [
    'dramatiq_crontab',
    # ...
]

Finally, you lauch the scheduler in a separate process:

python3 manage.py crontab

Setup Redis as a lock backend (optional)

If you use Redis as a broker, you can use Redis as a lock backend as well. The lock backend is used to prevent multiple instances of the scheduler from running at the same time. This is important if you have multiple instances of your application running.

# settings.py
DRAMATIQ_CRONTAB = {
    "REDIS_URL": "redis://localhost:6379/0",
}

Usage

# tasks.py
import dramatiq
from dramatiq_crontab import cron


@cron("*/5 * * * *")  # every 5 minutes
@dramatiq.actor
def my_task():
    my_task.logger.info("Hello World")

Interval

If you want to run a task more frequently than once a minute, you can use the interval decorator.

# tasks.py
import dramatiq
from dramatiq_crontab import interval


@interval(seconds=30)
@dramatiq.actor
def my_task():
    my_task.logger.info("Hello World")

Please note that the interval is relative to the time the scheduler is started. For example, if you start the scheduler at 12:00:00, the first run will be at 12:00:30. However, if you restart the scheduler at 12:00:15, the first run will be at 12:00:45.

Sentry Cron Monitors

If you use Sentry you can add cron monitors to your tasks. The monitor's slug will be the actor's name. Like my_task in the example above.

The crontab command

$ python3 manage.py crontab --help
usage: manage.py crontab [-h] [--no-task-loading] [--no-heartbeat] [--version] [-v {0,1,2,3}]
                         [--settings SETTINGS] [--pythonpath PYTHONPATH] [--traceback] [--no-color]
                         [--force-color] [--skip-checks]

Run dramatiq task scheduler for all tasks with the `cron` decorator.

options:
  -h, --help            show this help message and exit
  --no-task-loading     Don't load tasks from installed apps.
  --no-heartbeat        Don't start the heartbeat actor.