actor

生命周期

  • preStart()和postStop可用用来初始化和消息处理后清理资源
  • preRestart()和postRestop()可用用于异常重启时的一些预操作

lifecycle

Actor创建

ActorRef aggregateActor = getContext().actorOf(Props.create(AggregateActor.class),"AggregateActor");

带构造函数的创建

ActorRef reduceActor = getContext().actorOf(Props.create(ReduceActor.class,aggregateActor).withRouter(new RoundRobinPool(5)),"reduceActor");

异步调用

Future order = Patterns.ask(orderActor,num,timeout);

执行上下文

为了运行回调和操作，Futures 需要有一个ExecutionContext，它与java.util.concurrent.Executor很相像. 如果你在作用域内有一个ActorSystem，它会把自己的派发器用作ExecutionContext，或者你也可以用ExecutionContext伴生对象提供的工厂方法来将Executors和ExecutorServices进行包装，或者甚至创建自己的实例。

    final ExecutionContext ec = getContext().system().dispatcher();

转换

sequence和traverse两个辅助方法可以帮助处理更复杂的情况。这两个方法都是用来将T[Future[A]]转换为Future[T[A]]。

Future.sequence将输入的List[Future[Int]]转换为Future[List[Int]]. 这样我们就可以将map直接作用于List[Int]，从而得到List的总和。

        final Future<Iterable<Object>> aggregate = Futures.sequence(futures,getContext().system().dispatcher());

发送Future到Actor To send the result of a Future to an Actor, you can use the pipe construct:

    Patterns.pipe(msg,ec).to(actor);

消息转发

forward message将消息从一个actor路由到另一个actor，用于负载均衡，或者路由。

actor.forward(message, getContext());

终止Actor

  • System.shutdown()方法，终止所有actor和actor系统
  • 发送poisonPill()消息，它会放入mailbox,只到处理到它，duang,gave over.
  • getContext.stop(self)

stop

  1. Actor stops processing the mailbox messages.
  2. Actor sends the STOP signal to all the children.
  3. Actor waits for termination message from all its children.
  4. Next, Actor starts the self-termination process that involves the following: Invoking the postStop() method Dumping the attached mailbox Publishing the terminated message on DeathWatch Informing the supervisor about self-terminationld

Actors are stopped in the following ways: When the actor system calls the shutdown() method, this technique shuts down all the actors and the actor system. By sending a Poi sonPi l l message to an actor—Poi sonPi l l is like any message that goes and sits in the mailbox of the actor. A Poi sonPi l l message is processed by initiating the shutdown of the actor. By calling context .stop(self) for stopping itself and calling context . stop(chi ld) to stop the child actors.

Killing Actor

  • 发送kill()消息，被杀的Actor会发送异常往上传递。

例子

有一个异步调用的例子，用到了Future,转换，Patterns.pipe

参阅：FutureActor