Janne Rönkkö bca22054df Fix concurrency issue in timeout timer value processing
According to multiprocessing documentation for Value
(https://docs.python.org/3/library/multiprocessing.html#multiprocessing.Value)
reads and writes are protected with lock when the lock argument is True
(the default) or the lock argument is an instance of Lock or RLock. The
documentation states that operations like += are not atomic as that
involves reading and writing.

On the worker side the critical section includes also storing finished task
result because the timeout could happen after the task function has
finished but before the result has been stored and timer.value has been
updated to tell the guard process that the task has been finished.

On the guard side the critical section includes all checks done to see
if the worker has timed out or died and the actual reincarnation function
because the worker could update timer value to -1 (idle) or -2 (recycle)
after the guard has seen timer value 0 (timeout) and is going to terminate
the worker.
2019-01-28 08:39:56 +02:00
2018-08-05 19:23:32 +02:00
2019-01-16 15:03:01 +01:00
2015-06-14 14:37:08 +02:00
2018-08-05 19:19:47 +02:00
2015-09-19 15:16:36 +02:00
2018-08-14 13:28:33 +02:00
2018-08-29 19:03:53 +02:00

.. image:: docs/_static/logo.png
    :align: center
    :alt: Q logo
    :target: https://django-q.readthedocs.org/

A multiprocessing distributed task queue for Django
---------------------------------------------------

|image0| |image1| |docs| |image2|

Features
~~~~~~~~

-  Multiprocessing worker pool
-  Asynchronous tasks
-  Scheduled and repeated tasks
-  Encrypted and compressed packages
-  Failure and success database or cache
-  Result hooks, groups and chains
-  Django Admin integration
-  PaaS compatible with multiple instances
-  Multi cluster monitor
-  Redis, Disque, IronMQ, SQS, MongoDB or ORM
-  Rollbar and Sentry support

Requirements
~~~~~~~~~~~~

-  `Django <https://www.djangoproject.com>`__ > = 1.11.11
-  `Django-picklefield <https://github.com/gintas/django-picklefield>`__
-  `Arrow <https://github.com/crsmithdev/arrow>`__
-  `Blessed <https://github.com/jquast/blessed>`__

Tested with: Python 3.6. 3.7 Django 1.11.x and 2.1.x

.. warning:: Since Python 3.7 `async` became a reserved keyword and was refactored to `async_task`

Brokers
~~~~~~~
- `Redis <https://django-q.readthedocs.org/en/latest/brokers.html#redis>`__
- `Disque <https://django-q.readthedocs.org/en/latest/brokers.html#disque>`__
- `IronMQ <https://django-q.readthedocs.org/en/latest/brokers.html#ironmq>`__
- `Amazon SQS <https://django-q.readthedocs.org/en/latest/brokers.html#amazon-sqs>`__
- `MongoDB <https://django-q.readthedocs.org/en/latest/brokers.html#mongodb>`__
- `Django ORM <https://django-q.readthedocs.org/en/latest/brokers.html#django-orm>`__

Installation
~~~~~~~~~~~~

-  Install the latest version with pip::

    $ pip install django-q


-  Add `django_q` to your `INSTALLED_APPS` in your projects `settings.py`::

       INSTALLED_APPS = (
           # other apps
           'django_q',
       )

-  Run Django migrations to create the database tables::

    $ python manage.py migrate

-  Choose a message `broker <https://django-q.readthedocs.org/en/latest/brokers.html>`__ , configure and install the appropriate client library.

Read the full documentation at `https://django-q.readthedocs.org <https://django-q.readthedocs.org>`__


Configuration
~~~~~~~~~~~~~

All configuration settings are optional. e.g:

.. code:: python

    # settings.py example
    Q_CLUSTER = {
        'name': 'myproject',
        'workers': 8,
        'recycle': 500,
        'timeout': 60,
        'compress': True,
        'cpu_affinity': 1,
        'save_limit': 250,
        'queue_limit': 500,
        'label': 'Django Q',
        'redis': {
            'host': '127.0.0.1',
            'port': 6379,
            'db': 0, }
    }

For full configuration options, see the `configuration documentation <https://django-q.readthedocs.org/en/latest/configure.html>`__.

Management Commands
~~~~~~~~~~~~~~~~~~~

Start a cluster with::

    $ python manage.py qcluster

Monitor your clusters with::

    $ python manage.py qmonitor

Check overall statistics with::

    $ python manage.py qinfo

Creating Tasks
~~~~~~~~~~~~~~

Use `async_task` from your code to quickly offload tasks:

.. code:: python

    from django_q.tasks import async_task, result

    # create the task
    async_task('math.copysign', 2, -2)

    # or with a reference
    import math.copysign

    task_id = async_task(copysign, 2, -2)

    # get the result
    task_result = result(task_id)

    # result returns None if the task has not been executed yet
    # you can wait for it
    task_result = result(task_id, 200)

    # but in most cases you will want to use a hook:

    async_task('math.modf', 2.5, hook='hooks.print_result')

    # hooks.py
    def print_result(task):
        print(task.result)

For more info see `Tasks <https://django-q.readthedocs.org/en/latest/tasks.html>`__


Schedule
~~~~~~~~

Schedules are regular Django models. You can manage them through the
Admin page or directly from your code:

.. code:: python

    # Use the schedule function
    from django_q.tasks import schedule

    schedule('math.copysign',
             2, -2,
             hook='hooks.print_result',
             schedule_type=Schedule.DAILY)

    # Or create the object directly
    from django_q.models import Schedule

    Schedule.objects.create(func='math.copysign',
                            hook='hooks.print_result',
                            args='2,-2',
                            schedule_type=Schedule.DAILY
                            )

    # Run a task every 5 minutes, starting at 6 today
    # for 2 hours
    import arrow

    schedule('math.hypot',
             3, 4,
             schedule_type=Schedule.MINUTES,
             minutes=5,
             repeats=24,
             next_run=arrow.utcnow().replace(hour=18, minute=0))

For more info check the `Schedules <https://django-q.readthedocs.org/en/latest/schedules.html>`__ documentation.


Testing
~~~~~~~

To run the tests you will need the following in addition to install requirements:

* `py.test <http://pytest.org/latest/>`__
* `pytest-django <https://github.com/pytest-dev/pytest-django>`__
* disque from https://github.com/antirez/disque.git
* Redis
* MongoDB

The following commands can be used to run the tests:

```
# Create virtual environment
python -m venv venv

# Install requirements
venv/bin/pip install -r requirements.txt

# Install test dependencies
venv/bin/pip install pytest pytest-django

# Install django-q
venv/bin/python setup.py develop


# Run required services (you need to have docker-compose installed)
docker-compose -f test-services-docker-compose.yaml up -d

# Run tests
venv/bin/pytest

# Stop the services required by tests (when you no longer plan to run tests)
docker-compose -f test-services-docker-compose.yaml down

```


Locale
~~~~~~

Currently available in English and French.
Translation pull requests are always welcome.

Todo
~~~~

-  Better tests and coverage
-  Less dependencies?

Acknowledgements
~~~~~~~~~~~~~~~~

-  Django Q was inspired by working with
   `Django-RQ <https://github.com/ui/django-rq>`__ and
   `RQ <https://github.com/ui/django-rq>`__
-  Human readable hashes by
   `HumanHash <https://github.com/zacharyvoase/humanhash>`__
-  Redditors feedback at `r/django <https://www.reddit.com/r/django/>`__

.. |image0| image:: https://travis-ci.org/Koed00/django-q.svg?branch=master
   :target: https://travis-ci.org/Koed00/django-q
.. |image1| image:: http://codecov.io/github/Koed00/django-q/coverage.svg?branch=master
   :target: http://codecov.io/github/Koed00/django-q?branch=master
.. |image2| image:: http://badges.gitter.im/Join%20Chat.svg
   :target: https://gitter.im/Koed00/django-q
.. |docs| image:: https://readthedocs.org/projects/docs/badge/?version=latest
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    :scale: 100
    :target: https://django-q.readthedocs.org/
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A multiprocessing distributed task queue for Django based on Django-Q
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