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    <p>A while ago I wrote <a href="http://vasilrem.com/blog/software-development/fault-tolerance-primitives-in-scala-links-and-traps/" rel="nofollow">a post</a> on linking actors in Scala. Actor linking is an idiomatic [and the easiest] way to monitor actors in Erlang, Scala Actors and other actor libraries. By defalt, when you link 2 actors, and one of them dies, another immediately dies too (unless the actor traps/handles exit signal):</p> <pre><code>scala&gt; case object Stop defined module Stop scala&gt; scala&gt; val actor1 = actor { | loop { | react { | case Stop =&gt; | println("Actor 1: stop") | exit() | case msg =&gt; println(msg) | } | } | } actor1: scala.actors.Actor = scala.actors.Actor$$anon$1@1feea62 scala&gt; scala&gt; val actor2 = actor { | link(actor1) | self.trapExit = true | loop { | react { | case msg =&gt; println(msg) | } | } | } actor2: scala.actors.Actor = scala.actors.Actor$$anon$1@1e1c66a scala&gt; actor1.start res12: scala.actors.Actor = scala.actors.Actor$$anon$1@1feea62 scala&gt; actor2.start res13: scala.actors.Actor = scala.actors.Actor$$anon$1@1e1c66a scala&gt; actor1 ! Stop Actor 1: stop scala&gt; Exit(scala.actors.Actor$$anon$1@1feea62,'normal) // Actor 2 received message, when Actor1 died </code></pre> <p>A more sophisticated and flexible way is using supervisors (supervisor behavior in Erlang, <strong><a href="http://doc.akkasource.org/fault-tolerance-scala#Supervision" rel="nofollow">actor supervisors</a></strong> in Akka Actors library, etc). A supervisor (being itself an actor) monitors a number of other actors, and restarts them with regards to a specified strategy (restart all actors, if one dies; restart just one actor, when it dies).</p>
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    1. POScala, check if Actor has exited
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    1. USVasil Remeniuk
    1. USVasil Remeniuk
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    1. COlinking is far from perfect. Firstly, I believe that if you attempt to link to an actor which has already exited, you will not receive notification. Secondly, linking to an actor which falls over before it enters any kind of react/receive loop also misses any callbacks.
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    2. COLinking is idiomatic. In the both cases you mentioned, before linking it makes sense to call `getState`, and make sure that actor's state is different from 'terminated'.
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      1. USVasil Remeniuk
    3. COVasil, can you elaborate on getState? If I can check to see if an actor has terminated, that will also be a good solution for me. *edit* Okay, I looked at this link: http://www.scala-lang.org/api/current/index.html , and I see theres an enumerate. I'm guessing randomActorObject.getState==State.Terminated would be the check I am looking for.
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