Management of user-triggered asynchronous tasks in Django projects
django-user-tasks is a reusable Django application for managing user-triggered asynchronous tasks. It provides a status page for each such task, which includes a meaningful progress indicator if the task is currently being executed and provides any appropriate text and/or links for output once the task is complete.
In Open edX, such tasks include operations such as exporting or importing a course, sending an email to all the students in a course, uploading a video, and other tasks which often take too long to perform during a single web request (as outlined in OEP-3). However, this has been written with the intention of being useful in a variety of Django projects outside the Open edX platform as well.
Note that this library was created as a consolidation of lessons learned from implementing such tasks in various parts of the Open edX code base. They don’t yet all use this library, but the plan is to over time refactor many of them to do so.
django-user-tasks is currently a wrapper for Celery (although the hope is that it could also be extended to also support channels and other asynchronous task queues). By extending the provided UserTask class (or adding UserTaskMixin to an existing Task subclass) and providing a user_id task argument, the task’s status is stored in a database table separate from the Celery broker and result store. This UserTaskStatus model allows for full database queries of the tasks that users are most likely to care about while not imposing any restrictions on the Celery configuration most appropriate for the site’s overall needs for asynchronous task processing.
Most of the status updating is handled automatically via Celery’s signals mechanism, but it can be enhanced by:
- Overriding the UserTaskMixin methods such as generate_name and calculate_total_steps for particular types of tasks
- Calling some of the UserTaskStatus methods like increment_completed_steps and set_state from the task implementation
- Saving task output as instances of the UserTaskArtifact model
The full documentation is at https://django-user-tasks.readthedocs.org.
The code in this repository is licensed under the Apache Software License 2.0 unless otherwise noted.
Please see LICENSE.txt for details.
How To Contribute
Contributions are very welcome.
Please read How To Contribute for details.
Even though they were written with edx-platform in mind, the guidelines should be followed for Open edX code in general.
Reporting Security Issues
Please do not report security issues in public. Please email firstname.lastname@example.org.
Have a question about this repository, or about Open edX in general? Please refer to this list of resources if you need any assistance.
[0.1.5] - 2017-08-03
- Added testing/support for Django 1.11.
[0.1.4] - 2017-01-30
- Slightly improved handling of tasks which start before their status records are committed (due to database transactions). Also documented how to avoid this problem in the first place.
[0.1.3] - 2017-01-03
- Tasks which were explicitly canceled, failed, or retried no longer have their status changed to Succeeded just because the task exited cleanly.
- Celery tasks which fail to import cleanly by name (because they use a custom name which isn’t actually the fully qualified task name) are now just ignored in the before_task_publish signal handler.
[0.1.2] - 2016-12-05
- Add a migration to explicitly reference the setting for artifact file storage. This setting is likely to vary between installations, but doesn’t affect the generated database schema. This change should prevent makemigrations from creating a new migration whenever the setting value changes.
[0.1.1] - 2016-10-11
- Fix Travis configuration for PyPI deployments.
- Switch from the Read the Docs Sphinx theme to the Open edX one for documentation.
[0.1.0] - 2016-10-07
- First attempt to release on PyPI.
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