Urd is a scheduler for Django projects. Some features:

• schedule < 1m time slots
• single concurrent execution [#single]_
• fast enable/disable [#fastdisable]_
• simple deployment
• no extra dependencies beyond Django

.. [#single]

If tasks take longer to execute than the time to the next execution slot, you get a warning on the next execution. But not simultaneous execution or wild buildup of queues. There is no queue.

.. [#fastdisable]

It's vitally important to be able to stop a runaway process. With the ``heartbeat``, and with the worker reading the database state before executing, it's easy and fast to disable a job.

• Install urd pip install urd
• Add urd to INSTALLED_APPS
• Run manage.py migrate
• Start the scheduler with manage.py monitor

• Define a tasks.py module in the app that should have tasks.
• Create a function like this:

.. code-block:: python

@schedulable_task
def my_task(heartbeat):
    for foo in bar:
        heartbeat()
        do_some_task()

Calling heartbeat() regularly is important to make the task cancellable in a timely manner.

Now define a task in the iommi admin. It will be enabled pretty much as soon as you save.

Urd ships with integration for the iommi <https://docs.iommi.rocks>_ admin.

• Cron didn't work for me because I need to execute a function more often than once a minute
• Cron also doesn't work for me because if you do once per minute, and the task takes two minutes, you get TWO executing processes of that task for a while. This can be disastrous for a few reasons, and can cause things to spiral out of control.
• Celery/django-q are task queues, not schedulers. They have scheduler components, but they don't have a way to ensure only one process at a time runs a specific task.
• Django-q doesn't allow schedules that execute more often than once per minute
• Django-q caused me a lot of problems where the schedule seemed to put future items in the queue, and I couldn't make it stop trying to execute them.

Urd (or Urðr, or Wyrd) is one of the Norns, the goddesses who weave the destiny of gods and humans.