72 lines
2.6 KiB
ReStructuredText
72 lines
2.6 KiB
ReStructuredText
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.. _scheduler-java:
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##################
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Scheduler (Java)
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##################
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Sometimes the need for making things happen in the future arises, and where do you go look then?
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Look no further than ``ActorSystem``! There you find the :meth:`scheduler` method that returns an instance
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of akka.actor.Scheduler, this instance is unique per ActorSystem and is used internally for scheduling things
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to happen at specific points in time. Please note that the scheduled tasks are executed by the default
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``MessageDispatcher`` of the ``ActorSystem``.
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You can schedule sending of messages to actors and execution of tasks (functions or Runnable).
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You will get a ``Cancellable`` back that you can call :meth:`cancel` on to cancel the execution of the
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scheduled operation.
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.. warning::
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The default implementation of ``Scheduler`` used by Akka is based on the Netty ``HashedWheelTimer``.
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It does not execute tasks at the exact time, but on every tick, it will run everything that is overdue.
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The accuracy of the default Scheduler can be modified by the "ticks-per-wheel" and "tick-duration" configuration
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properties. For more information, see: `HashedWheelTimers <http://www.cse.wustl.edu/~cdgill/courses/cs6874/TimingWheels.ppt>`_.
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Some examples
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-------------
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Schedule to send the "foo"-message to the testActor after 50ms:
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.. includecode:: code/docs/actor/SchedulerDocTestBase.java
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:include: imports1
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.. includecode:: code/docs/actor/SchedulerDocTestBase.java
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:include: schedule-one-off-message
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Schedule a Runnable, that sends the current time to the testActor, to be executed after 50ms:
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.. includecode:: code/docs/actor/SchedulerDocTestBase.java
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:include: schedule-one-off-thunk
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Schedule to send the "Tick"-message to the ``tickActor`` after 0ms repeating every 50ms:
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.. includecode:: code/docs/actor/SchedulerDocTestBase.java
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:include: imports1,imports2
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.. includecode:: code/docs/actor/SchedulerDocTestBase.java
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:include: schedule-recurring
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From ``akka.actor.ActorSystem``
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-------------------------------
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.. includecode:: ../../../akka-actor/src/main/scala/akka/actor/ActorSystem.scala
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:include: scheduler
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The Scheduler interface
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-----------------------
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.. includecode:: ../../../akka-actor/src/main/scala/akka/actor/Scheduler.scala
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:include: scheduler
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The Cancellable interface
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-------------------------
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This allows you to ``cancel`` something that has been scheduled for execution.
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.. warning::
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This does not abort the execution of the task, if it had already been started.
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.. includecode:: ../../../akka-actor/src/main/scala/akka/actor/Scheduler.scala
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:include: cancellable
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