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Actor model an approach to concurrency 1.0 (freiburg)
- 1. The Actor Model 1 An alternative approach to concurrency Lorenzo Nicora Senior Consultant @ OpenCredo @nicusX https://opencredo.com/author/lorenzo/
- 2. ✓ (1973) Carl Hewitt: “A Universal Modular Actor Formalism for Artificial Intelligence” 2 A bit of History… 1973 2009 ✓ (2009) Akka toolkit, Scala/Java ✓ (1986) Ericsson: Erlang Lorenzo Nicora Actor Model
- 3. According to Alan Kay, author of Smalltalk and inventor of the “Object-Orientation”: 3 The original idea of Object An “Object” ✓ Is the basic unit of object-oriented system ✓ Has its own state ✓ Communicate with others by sending and receiving messages* * in Java, C++, C# (derived from Simula, not Smalltalk) Objects interact by invoking methods 1980 Lorenzo Nicora Actor Model
- 4. An “Actor” is a computational entity that, in response to a message it receives, can concurrently: a) Send a finite number of messages to other actors b) Create a finite number of new actors c) Designate the behaviour to be used for the next message it receives. [implies a state] 4 The Actor Actor Actor Actor Mailbox Mailbox Mailbox Lorenzo Nicora Actor Model
- 5. Actors interacts only by messaging Actors react to messages 5 Actors are Reactive Lorenzo Nicora Actor Model
- 6. An Actor handles one message a time Never concurrently An Actor has a state State cannot be modified from outside the actor 6 Thread-safe An Actor is inherently thread-safe No Lock/Synchronisation on State Lorenzo Nicora Actor Model
- 7. 7 Supervision Actors are created by Actors Parent -> Child Lorenzo Nicora Actor Model
- 8. 8 Supervision Failure Handling • If a Child throws an Exception, the Supervisor get notified • Supervision Strategy: e.g. relaunch, abandon… Failure is always handled consistently Parent = Supervisor Lorenzo Nicora Actor Model
- 9. 9 Lightweight Actor is lightweight Creating an Actor has little overhead beyond creating an Object Lorenzo Nicora Actor Model
- 10. Non-blocking implementation of Request/Response pattern with multiple downstream collaborators 10 Example: Non-blocking Request/Response • One-Actor-per-Request pattern • Enterprise Integration Patterns: ✴ Request/Reply ✴ Return Address ✴ Scatter-Gather, Aggregators ✴ Round-robin Message Router Lorenzo Nicora Actor Model
- 11. 11 Example: Non-blocking Request/Response Lorenzo Nicora Actor Model
- 12. 12 Example: Non-blocking Request/Response Lorenzo Nicora Actor Model
- 13. 13 Example: Non-blocking Request/Response Lorenzo Nicora Actor Model
- 14. 14 Example: Non-blocking Request/Response Lorenzo Nicora Actor Model
- 15. 15 Example: Non-blocking Request/Response Lorenzo Nicora Actor Model
- 16. 16 Example: Non-blocking Request/Response Lorenzo Nicora Actor Model
- 17. 17 Example: Non-blocking Request/Response Lorenzo Nicora Actor Model
- 18. 18 Example: Non-blocking Request/Response Lorenzo Nicora Actor Model
- 19. 19 Example: Non-blocking Request/Response Lorenzo Nicora Actor Model
- 20. 20 Example: Non-blocking Request/Response Lorenzo Nicora Actor Model
- 21. 21 Example: Non-blocking Request/Response Lorenzo Nicora Actor Model
- 22. 22 Conclusions Actor model: an alternative approach to concurrency Actors, Threads + Business logic implementation + inherently thread-safe - A new programming paradigm - to learn Lorenzo Nicora Actor Model
- 23. 23 Lorenzo Nicora Actor Model