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Introduction to the Actor Model
The document discusses the actor model, a computational model established by Dr. Carl Hewitt in the 1970s, emphasizing its application in robotics and AI. It describes how actors communicate through immutable messages without shared state and details implementations in various programming languages and systems, including the Akka framework for JVM. The conclusion highlights that Akka builds on the actor model, offering features like remoting and clustering while maintaining its foundational principles.
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Introduction to the Actor Model
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- 2. WHO? Mike Nash - VPCapabilities - BoldRadius Solutions
- 3. THE ACTOR MODEL Amodel of computation An architectural approach Implementations
- 4. DR. CARL HEWITT ▸Designed the Planner language ▸ "pattern-directed invokation from assertions and goals" ▸ used in robotics and AI ▸ The Actor Model ▸ Work spans 30 years ▸ Initial paper in 1973 with Peter Bishop and Richard Steiger ▸ In collaboration with MITs AI Lab
- 5. DR. CARL HEWITT ▸Languages ▸ Scheme ▸ ACT-1 ▸ SALSA ▸ Caltrop ▸ ActorScript
- 6. THE ACTOR MODEL Amathematical model of concurrent computation where... ▸ actors are the universal primitive of computation ▸ An actor ▸ receives messages and acts on them ▸ sends messages
- 7. THE ACTOR MODEL Inspiredby physics, general relativity and quantum mechanics Actor model theory explores theoretical topics in the actor model No shared state between actors Actors encapsulate state
- 8. RECEIVES MESSAGES ▸ Onlyway to interact with an actor is to send it a message ▸ Messages should be immutable ▸ All computation is in response to a message ▸ An actor is potential energy, a message turns it into kinetic energy
- 9. SENDS MESSAGES An actorcan send messages to other actors This is its only way to communicate Messages are processed sequentially, concurrent to the sender
- 10. CREATES CHILD ACTORS Actorscreate other actors to handle sub-tasks Parent communicates with them via messages as usual
- 11. CHANGES BEHAVIOR An actorcan change its behavior for subsequent messages This provides the basis for a finite state machine
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- 13. HARDWARE Caltech Cosmic Cube -1981 - 64 Intel 8086/87 processors - 6-dimensional hypercube network
- 14. HARDWARE J-Machine - 1988 - MITVLSI Architecture group - Designed for concurrent smalltalk and the actor model
- 15. SOFTWARE ▸ Erlang ▸ Elixir ▸Ada Tasks ▸ Pony ▸ Common Lisp Actors ▸ Akka
- 16. AKKA A practical applicationof the Actor Model on the JVM Large ecosystem of related libraries
- 17. AKKA CORE Actors withina single JVM Written in Scala Interoperable from Java, Clojure, Groovy Use any JVM library Supports pub/sub as well as point-to-point
- 18. TESTKIT ▸ Allows asynchronousactors to be tested synchronously ▸ Allows mock actors to be used as test probes ▸ Allows internal actor methods to be tested ▸ Allows asynchronous actors to be tested together
- 19. AGENTS ▸ Encapsulate asingle value ▸ Conflict free reads ▸ Queued writes ▸ Writes expressed as a function (_ + 1)
- 20. AKKA REMOTING ▸ Actorsin different JVMs can exchange messages ▸ Pluggable serialization ▸ Pluggable transport
- 21. AKKA CLUSTER ▸ Buildson remoting ▸ Avoid fixed addressing ▸ Handles cluster membership ▸ Cluster-aware routers ▸ Cluster singletons ▸ Auto fail-over ▸ Cluster events available
- 22. AKKA CLUSTER SHARDING ▸Builds on cluster ▸ Node affinity for messages ▸ No single point of failure ▸ Supports distributed domain
- 23. AKKA DATA REPLICATION ▸Supports automatic replication of data in a cluster ▸ Data must be represented with conflict-free replicated types ▸ Eventually consistent with short lag
- 24. AKKA HTTP ▸ Exposeactors to the web ▸ Client and server ▸ Routing ▸ Requests and responses as messages ▸ Includes HTTP TestKit
- 25. AKKA STREAMS ▸ Solvesthe back-pressure problem ▸ DSL to define flows ▸ Sources and Sinks ▸ Akka HTTP builds on this
- 26. AKKA CONTRIB ▸ Communitycontributions to Akka ▸ Reliable proxy ▸ Message throttling ▸ Aggregators ▸ Receive pipeline
- 27. AKKA TYPED ▸ Nextmajor version ▸ Actors support types ▸ Both messages and behaviors ▸ Under active development
- 28. CONCLUSION The Actor modelpredates Akka Akka provides the actor model on the JVM Akka optionally provides remoting, clustering and much more