Scala laboratory: Globus. iteration #3
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The document outlines goals for iteration #3 of the Globus project, focusing on transforming server-side architecture to utilize actor-based systems for improved concurrency and scalability. It explains key concepts of actors, supervisors, and dispatchers in the Akka framework, including how actors can handle failures through supervision. Real-world examples and links are provided for further illustration of these concepts.
![Supervisors in Akka
1. class FirstActor extends Actor {
2. val child = context.actorOf(Props[MyActor], name =
"myChild")
3. // plus some behavior ...
4. }](https://image.slidesharecdn.com/scalalaboratory-150319230508-conversion-gate01/85/Scala-laboratory-Globus-iteration-3-8-320.jpg)
Scala laboratory: Globus. iteration #3
- 2. Goals of the iteration ● change server-side of Globus Project to use Actors ○ if you already have layer of services, they can be transformed into actors ○ if you don’t have services, refactor the the code
- 3. Actor’s concept ● invented in 70th ● popularized in 80th in Erlang (OTP Framework)
- 4. Why Actors? ● straightforward concurrency ● simple design ● easy to scale to multiple nodes ○ location transparency ● toolkit for building fault-tolerant systems
- 5. Actor-based systems Key concepts: ● actor ● supervisor ● dispatcher
- 6. Actors in Akka 1. class MyActor extends Actor { 2. val log = Logging(context.system, this) 3. def receive = { 4. case Ping(message) => log.info(message) 5. } 6. }
- 7. Supervisors ● “when someone dies, others will notice”, Joe Armstrong ● when error occurs in an actor, it dies ● 2 actors may be linked ● when 1 actor dies, another dies as well ○ or, it may handle the error (supervise another actor)
- 8. Supervisors in Akka 1. class FirstActor extends Actor { 2. val child = context.actorOf(Props[MyActor], name = "myChild") 3. // plus some behavior ... 4. }
- 9. Supervisors in Akka, II ● when child dies, supervisor receives Terminated(`child`)
- 10. Supervisors: real-world example ● see http://www.slideshare.net/remeniuk/a- million-bots-cant-be-wrong (slides 10-19)
- 11. Dispatchers ● provide “resources” for actors to process the message ○ Dispatcher ○ PinnedDispatcher ○ BalancingDispatcher ○ CallingThreadDispatcher
- 12. Dispatchers: real-world example ● http://www.slideshare.net/remeniuk/a-million- bots-cant-be-wrong (slides 35-42)