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POHow to Cancel an Akka actor?
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copied!<p>I have an akka actor(worker) that receives a request and replies to it. The request processing can take 3-60 minutes. Caller(also an actor) is currently using !!! and waiting on future.get, however the design of Caller actor can be changed if required. Also, I'm currently using EventDriven dispatcher.</p> <p>How do i Cancel(user initiated) the request processing so that the worker actor is freed up and returns to the ready state to receive new requests? I was hoping for a method similar to java.util.concurrent.Future's cancel method but couldn't find in Akka 1.1.3</p> <p><strong>Edit:</strong></p> <p>We tried to get the behavior we are looking for with <code>completeWithException</code>: </p> <pre><code>object Cancel { def main(args: Array[String]) { val actor = Actor.actorOf[CancelActor].start EventHandler.info(this, "Getting future") val future = (actor ? "request").onComplete(x => EventHandler.info(this, "Completed!! " + x.get)) Thread.sleep(500L) EventHandler.info(this, "Cancelling") future.completeWithException(new Exception("cancel")) EventHandler.info(this, "Future is " + future.get) } } class CancelActor extends Actor { def receive = { case "request" => EventHandler.info(this, "start") (1 to 5).foreach(x => { EventHandler.info(this, "I am a long running process") Thread.sleep(200L) }) self reply "response" EventHandler.info(this, "stop") } } </code></pre> <p>But that did not stop the long-running process.</p> <pre><code> [INFO] [9/16/11 1:46 PM] [main] [Cancel$] Getting future [INFO] [9/16/11 1:46 PM] [akka:event-driven:dispatcher:global-2] [CancelActor] start [INFO] [9/16/11 1:46 PM] [akka:event-driven:dispatcher:global-2] [CancelActor] I am a long running process [INFO] [9/16/11 1:46 PM] [akka:event-driven:dispatcher:global-2] [CancelActor] I am a long running process [INFO] [9/16/11 1:46 PM] [akka:event-driven:dispatcher:global-2] [CancelActor] I am a long running process [INFO] [9/16/11 1:46 PM] [main] [Cancel$] Cancelling [ERROR] [9/16/11 1:46 PM] [akka:event-driven:dispatcher:global-7] [ActorCompletableFuture] java.lang.Exception: cancel at kozo.experimental.Cancel$.main(Cancel.scala:15) ... [INFO] [9/16/11 1:46 PM] [akka:event-driven:dispatcher:global-2] [CancelActor] I am a long running process [INFO] [9/16/11 1:46 PM] [akka:event-driven:dispatcher:global-2] [CancelActor] I am a long running process [INFO] [9/16/11 1:46 PM] [akka:event-driven:dispatcher:global-2] [CancelActor] stop </code></pre> <p>In contrast consider the behavior of of a java.util.concurrent.Future:</p> <pre><code>object Cancel2 { def main(args: Array[String]) { val executor: ExecutorService = Executors.newSingleThreadExecutor() EventHandler.info(this, "Getting future") val future = executor.submit(new Runnable { def run() { EventHandler.info(this, "start") (1 to 5).foreach(x => { EventHandler.info(this, "I am a long running process") Thread.sleep(200L) }) } }) Thread.sleep(500L) EventHandler.info(this, "Cancelling") future.cancel(true) EventHandler.info(this, "Future is " + future.get) } } </code></pre> <p>Which does stop the long running process</p> <pre><code> [INFO] [9/16/11 1:48 PM] [main] [Cancel2$] Getting future [INFO] [9/16/11 1:48 PM] [pool-1-thread-1] [anon$1] start [INFO] [9/16/11 1:48 PM] [pool-1-thread-1] [anon$1] I am a long running process [INFO] [9/16/11 1:48 PM] [pool-1-thread-1] [anon$1] I am a long running process [INFO] [9/16/11 1:48 PM] [pool-1-thread-1] [anon$1] I am a long running process Exception in thread "main" java.util.concurrent.CancellationException ... [INFO] [9/16/11 1:48 PM] [main] [Cancel2$] Cancelling </code></pre>

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