778e210e17
Since the key 'old_state' is now standard across all notifications sent from flows, retries or tasks we can safely use it in the listeners without worrying about hitting key errors when it does not exist/is not provided. This also adds an example which shows how to use the dynamic logging listener to view this information. Change-Id: If4456440674347a3fe4972d9d0fa16ba8373ef9f
189 lines
5.9 KiB
ReStructuredText
189 lines
5.9 KiB
ReStructuredText
===========================
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Notifications and listeners
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===========================
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.. testsetup::
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from taskflow import task
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from taskflow.patterns import linear_flow
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from taskflow import engines
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--------
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Overview
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--------
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Engines provide a way to receive notification on task and flow state
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transitions, which is useful for monitoring, logging, metrics, debugging
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and plenty of other tasks.
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To receive these notifications you should register a callback with
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an instance of the :py:class:`~taskflow.types.notifier.Notifier`
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class that is attached to :py:class:`~taskflow.engines.base.Engine`
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attributes ``atom_notifier`` and ``notifier``.
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TaskFlow also comes with a set of predefined :ref:`listeners <listeners>`, and
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provides means to write your own listeners, which can be more convenient than
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using raw callbacks.
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--------------------------------------
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Receiving notifications with callbacks
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--------------------------------------
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Flow notifications
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------------------
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To receive notification on flow state changes use the
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:py:class:`~taskflow.types.notifier.Notifier` instance available as the
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``notifier`` property of an engine.
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A basic example is:
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.. doctest::
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>>> class CatTalk(task.Task):
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... def execute(self, meow):
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... print(meow)
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... return "cat"
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...
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>>> class DogTalk(task.Task):
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... def execute(self, woof):
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... print(woof)
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... return 'dog'
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...
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>>> def flow_transition(state, details):
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... print("Flow '%s' transition to state %s" % (details['flow_name'], state))
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...
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>>>
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>>> flo = linear_flow.Flow("cat-dog").add(
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... CatTalk(), DogTalk(provides="dog"))
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>>> eng = engines.load(flo, store={'meow': 'meow', 'woof': 'woof'})
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>>> eng.notifier.register("*", flow_transition)
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>>> eng.run()
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Flow 'cat-dog' transition to state RUNNING
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meow
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woof
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Flow 'cat-dog' transition to state SUCCESS
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Task notifications
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------------------
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To receive notification on task state changes use the
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:py:class:`~taskflow.types.notifier.Notifier` instance available as the
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``atom_notifier`` property of an engine.
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A basic example is:
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.. doctest::
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>>> class CatTalk(task.Task):
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... def execute(self, meow):
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... print(meow)
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... return "cat"
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...
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>>> class DogTalk(task.Task):
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... def execute(self, woof):
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... print(woof)
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... return 'dog'
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...
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>>> def task_transition(state, details):
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... print("Task '%s' transition to state %s" % (details['task_name'], state))
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...
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>>>
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>>> flo = linear_flow.Flow("cat-dog")
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>>> flo.add(CatTalk(), DogTalk(provides="dog"))
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<taskflow.patterns.linear_flow.Flow object at 0x...>
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>>> eng = engines.load(flo, store={'meow': 'meow', 'woof': 'woof'})
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>>> eng.task_notifier.register("*", task_transition)
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>>> eng.run()
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Task 'CatTalk' transition to state RUNNING
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meow
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Task 'CatTalk' transition to state SUCCESS
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Task 'DogTalk' transition to state RUNNING
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woof
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Task 'DogTalk' transition to state SUCCESS
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.. _listeners:
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---------
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Listeners
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---------
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TaskFlow comes with a set of predefined listeners -- helper classes that can be
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used to do various actions on flow and/or tasks transitions. You can also
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create your own listeners easily, which may be more convenient than using raw
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callbacks for some use cases.
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For example, this is how you can use
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:py:class:`~taskflow.listeners.printing.PrintingListener`:
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.. doctest::
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>>> from taskflow.listeners import printing
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>>> class CatTalk(task.Task):
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... def execute(self, meow):
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... print(meow)
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... return "cat"
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...
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>>> class DogTalk(task.Task):
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... def execute(self, woof):
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... print(woof)
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... return 'dog'
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...
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>>>
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>>> flo = linear_flow.Flow("cat-dog").add(
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... CatTalk(), DogTalk(provides="dog"))
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>>> eng = engines.load(flo, store={'meow': 'meow', 'woof': 'woof'})
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>>> with printing.PrintingListener(eng):
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... eng.run()
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...
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<taskflow.engines.action_engine.engine.SerialActionEngine object at ...> has moved flow 'cat-dog' (...) into state 'RUNNING' from state 'PENDING'
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<taskflow.engines.action_engine.engine.SerialActionEngine object at ...> has moved task 'CatTalk' (...) into state 'RUNNING' from state 'PENDING'
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meow
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<taskflow.engines.action_engine.engine.SerialActionEngine object at ...> has moved task 'CatTalk' (...) into state 'SUCCESS' from state 'RUNNING' with result 'cat' (failure=False)
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<taskflow.engines.action_engine.engine.SerialActionEngine object at ...> has moved task 'DogTalk' (...) into state 'RUNNING' from state 'PENDING'
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woof
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<taskflow.engines.action_engine.engine.SerialActionEngine object at ...> has moved task 'DogTalk' (...) into state 'SUCCESS' from state 'RUNNING' with result 'dog' (failure=False)
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<taskflow.engines.action_engine.engine.SerialActionEngine object at ...> has moved flow 'cat-dog' (...) into state 'SUCCESS' from state 'RUNNING'
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Basic listener
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--------------
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.. autoclass:: taskflow.listeners.base.Listener
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Printing and logging listeners
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------------------------------
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.. autoclass:: taskflow.listeners.base.DumpingListener
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.. autoclass:: taskflow.listeners.logging.LoggingListener
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.. autoclass:: taskflow.listeners.logging.DynamicLoggingListener
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.. autoclass:: taskflow.listeners.printing.PrintingListener
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Timing listener
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---------------
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.. autoclass:: taskflow.listeners.timing.TimingListener
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.. autoclass:: taskflow.listeners.timing.PrintingTimingListener
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Claim listener
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--------------
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.. autoclass:: taskflow.listeners.claims.CheckingClaimListener
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Hierarchy
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---------
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.. inheritance-diagram::
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taskflow.listeners.base.DumpingListener
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taskflow.listeners.base.Listener
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taskflow.listeners.claims.CheckingClaimListener
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taskflow.listeners.logging.DynamicLoggingListener
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taskflow.listeners.logging.LoggingListener
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taskflow.listeners.printing.PrintingListener
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taskflow.listeners.timing.PrintingTimingListener
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taskflow.listeners.timing.TimingListener
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:parts: 1
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