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
5.9 KiB
Notifications and listeners
from taskflow import task from taskflow.patterns import linear_flow from taskflow import engines
Overview
Engines provide a way to receive notification on task and flow state transitions, which is useful for monitoring, logging, metrics, debugging and plenty of other tasks.
To receive these notifications you should register a callback with an
instance of the :py~taskflow.types.notifier.Notifier class that is
attached to :py~taskflow.engines.base.Engine attributes
atom_notifier and notifier.
TaskFlow also comes with a set of predefined listeners <listeners>,
and provides means to write your own listeners, which can be more
convenient than using raw callbacks.
Receiving notifications with callbacks
Flow notifications
To receive notification on flow state changes use the :py~taskflow.types.notifier.Notifier instance available
as the notifier property of an engine.
A basic example is:
>>> class CatTalk(task.Task): ... def execute(self, meow): ... print(meow) ... return "cat" ... >>> class DogTalk(task.Task): ... def execute(self, woof): ... print(woof) ... return 'dog' ... >>> def flow_transition(state, details): ... print("Flow '%s' transition to state %s" % (details['flow_name'], state)) ... >>> >>> flo = linear_flow.Flow("cat-dog").add( ... CatTalk(), DogTalk(provides="dog")) >>> eng = engines.load(flo, store={'meow': 'meow', 'woof': 'woof'}) >>> eng.notifier.register("*", flow_transition) >>> eng.run() Flow 'cat-dog' transition to state RUNNING meow woof Flow 'cat-dog' transition to state SUCCESS
Task notifications
To receive notification on task state changes use the :py~taskflow.types.notifier.Notifier instance available
as the atom_notifier property of an engine.
A basic example is:
>>> class CatTalk(task.Task): ... def execute(self, meow): ... print(meow) ... return "cat" ... >>> class DogTalk(task.Task): ... def execute(self, woof): ... print(woof) ... return 'dog' ... >>> def task_transition(state, details): ... print("Task '%s' transition to state %s" % (details['task_name'], state)) ... >>> >>> flo = linear_flow.Flow("cat-dog") >>> flo.add(CatTalk(), DogTalk(provides="dog")) <taskflow.patterns.linear_flow.Flow object at 0x...> >>> eng = engines.load(flo, store={'meow': 'meow', 'woof': 'woof'}) >>> eng.task_notifier.register("*", task_transition) >>> eng.run() Task 'CatTalk' transition to state RUNNING meow Task 'CatTalk' transition to state SUCCESS Task 'DogTalk' transition to state RUNNING woof Task 'DogTalk' transition to state SUCCESS
Listeners
TaskFlow comes with a set of predefined listeners -- helper classes that can be used to do various actions on flow and/or tasks transitions. You can also create your own listeners easily, which may be more convenient than using raw callbacks for some use cases.
For example, this is how you can use :py~taskflow.listeners.printing.PrintingListener:
>>> from taskflow.listeners import printing >>> class CatTalk(task.Task): ... def execute(self, meow): ... print(meow) ... return "cat" ... >>> class DogTalk(task.Task): ... def execute(self, woof): ... print(woof) ... return 'dog' ... >>> >>> flo = linear_flow.Flow("cat-dog").add( ... CatTalk(), DogTalk(provides="dog")) >>> eng = engines.load(flo, store={'meow': 'meow', 'woof': 'woof'}) >>> with printing.PrintingListener(eng): ... eng.run() ... <taskflow.engines.action_engine.engine.SerialActionEngine object at ...> has moved flow 'cat-dog' (...) into state 'RUNNING' from state 'PENDING' <taskflow.engines.action_engine.engine.SerialActionEngine object at ...> has moved task 'CatTalk' (...) into state 'RUNNING' from state 'PENDING' meow <taskflow.engines.action_engine.engine.SerialActionEngine object at ...> has moved task 'CatTalk' (...) into state 'SUCCESS' from state 'RUNNING' with result 'cat' (failure=False) <taskflow.engines.action_engine.engine.SerialActionEngine object at ...> has moved task 'DogTalk' (...) into state 'RUNNING' from state 'PENDING' woof <taskflow.engines.action_engine.engine.SerialActionEngine object at ...> has moved task 'DogTalk' (...) into state 'SUCCESS' from state 'RUNNING' with result 'dog' (failure=False) <taskflow.engines.action_engine.engine.SerialActionEngine object at ...> has moved flow 'cat-dog' (...) into state 'SUCCESS' from state 'RUNNING'
Basic listener
taskflow.listeners.base.Listener
Printing and logging listeners
taskflow.listeners.base.DumpingListener
taskflow.listeners.logging.LoggingListener
taskflow.listeners.logging.DynamicLoggingListener
taskflow.listeners.printing.PrintingListener
Timing listener
taskflow.listeners.timing.TimingListener
taskflow.listeners.timing.PrintingTimingListener
Claim listener
taskflow.listeners.claims.CheckingClaimListener
Hierarchy
taskflow.listeners.base.DumpingListener taskflow.listeners.base.Listener taskflow.listeners.claims.CheckingClaimListener taskflow.listeners.logging.DynamicLoggingListener taskflow.listeners.logging.LoggingListener taskflow.listeners.printing.PrintingListener taskflow.listeners.timing.PrintingTimingListener taskflow.listeners.timing.TimingListener