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f5197ac912
Also moved Group, Iterable and Chain to their own pages because the Task page was getting too big. v0.7.11
105 lines
3.0 KiB
ReStructuredText
105 lines
3.0 KiB
ReStructuredText
.. py:currentmodule:: django_q
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Chains
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======
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Sometimes you want to run tasks sequentially. For that you can use the :func:`async_chain` function:
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.. code-block:: python
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# Async a chain of tasks
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from django_q.tasks import async_chain, result_group
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# the chain must be in the format
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# [(func,(args),{kwargs}),(func,(args),{kwargs}),..]
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group_id = async_chain([('math.copysign', (1, -1)),
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('math.floor', (1,))])
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# get group result
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result_group(group_id, count=2)
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A slightly more convenient way is to use a :class:`Chain` instance:
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.. code-block:: python
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# Chain async
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from django_q.tasks import Chain
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# create a chain that uses the cache backend
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chain = Chain(cached=True)
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# add some tasks
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chain.append('math.copysign', 1, -1)
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chain.append('math.floor', 1)
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# run it
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chain.run()
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print(chain.result())
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.. code-block:: python
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[-1.0, 1]
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Reference
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---------
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.. py:function:: async_chain(chain, group=None, cached=Conf.CACHED, sync=Conf.SYNC, broker=None)
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Async a chain of tasks. See also the :class:`Chain` class.
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:param list chain: a list of tasks in the format [(func,(args),{kwargs}), (func,(args),{kwargs})]
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:param str group: an optional group name.
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:param bool cached: run this against the cache backend
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:param bool sync: execute this inline instead of asynchronous
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.. py:class:: Chain(chain=None, group=None, cached=Conf.CACHED, sync=Conf.SYNC)
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A sequential chain of tasks. Acts as a convenient wrapper for :func:`async_chain`
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You can pass the task chain at construction or you can append individual tasks before running them.
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:param list chain: a list of task in the format [(func,(args),{kwargs}), (func,(args),{kwargs})]
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:param str group: an optional group name.
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:param bool cached: run this against the cache backend
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:param bool sync: execute this inline instead of asynchronous
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.. py:method:: append(func, *args, **kwargs)
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Append a task to the chain. Takes the same arguments as :func:`async`
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:return: the current number of tasks in the chain
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:rtype: int
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.. py:method:: run()
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Start queueing the chain to the worker cluster.
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:return: the chains group id
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.. py:method:: result(wait=0)
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return the full list of results from the chain when it finishes. Blocks until timeout or result.
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:param int wait: how many milliseconds to wait for a result
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:return: an unsorted list of results
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.. py:method:: fetch(failures=True, wait=0)
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get the task result objects from the chain when it finishes. Blocks until timeout or result.
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:param failures: include failed tasks
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:param int wait: how many milliseconds to wait for a result
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:return: an unsorted list of task objects
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.. py:method:: current()
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get the index of the currently executing chain element
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:return int: current chain index
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.. py:method:: length()
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get the length of the chain
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:return int: length of the chain |