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96 lines
2.6 KiB
ReStructuredText
96 lines
2.6 KiB
ReStructuredText
Django Q
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========
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A multiprocessing task queue application for Django
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---------------------------------------------------
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Status
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~~~~~~
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In Alpha and Python 3 only (for now). Everything should work, but the
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basic structure can still change. Main focus will be put on creating
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tests now.
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Architecture
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~~~~~~~~~~~~
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.. figure:: http://i.imgur.com/wTIeg2T.png
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:alt: Django Q schema
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Django Q schema
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.. code:: python
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async(func,*args,hook=None,**kwargs)
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Signed Tasks
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~~~~~~~~~~~~
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Tasks are first pickled to Json and then signed using Django's own
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signing module before being sent to a Redis list. This ensures that task
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packages on the Redis server can only be excuted and read by clusters
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and django servers who share the same secret key.
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Optionally, packages can be compressed before transport by setting
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``Q_COMPRESSED = True``
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Pusher
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~~~~~~
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The pusher process continously checks the Redis list for new task
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packages and pushes them on the Task Queue.
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Worker
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~~~~~~
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A worker process checks the package signing, unpacks the task, executes
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it and saves the return value. Irrespective of the failure or success of
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any of these steps, the package is then pushed onto the Result Queue.
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By default Django Q spawns a worker for each detected CPU on the host
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system. This can be overridden by setting ``Q_WORKERS = n``. With *n*
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being the numbe of desired worker processes.
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Monitor
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~~~~~~~
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The result monitor checks the Result Queue for processed packages and
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saves both failed and succesful packages to the Django database.
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By default only the last 100 succesful packages are kept in the
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database. This can be increased or decreased at will by settings
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``Q_SAVE_LIMIT = n``. With *n* being the desired number of records. Set
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``Q_SAVE_LIMIT = 0`` to save all results to the database. Failed
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packages are always saved.
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Sentinel
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~~~~~~~~
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The sentinel spawns all process and then checks the health of all
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workers, including the pusher and the monitor. Reincarnating processes
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if any may fail. In case of a stop signal, the sentinel will halt the
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pusher and instruct the workers and monitor to finish the remaining
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items , before exiting.
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Hooks
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~~~~~
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Packages can be assigned a hook function, upon completion of the package
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this function will be called with the Task object as the first argument.
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Management command
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~~~~~~~~~~~~~~~~~~
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Start the cluster with ``./manage.py qcluster``
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Admin integration
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~~~~~~~~~~~~~~~~~
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Django Q registers itself with the admin page to show failed and
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succesful tasks. From there task results can be read or deleted. If
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neccesary, failed tasks can be reintroduced to the queue.
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Todo
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~~~~
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I'll add to this README while I'm developing the various parts.
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