Short introduction to actor model with examples on Akka.NET

1. Introduction to actor model with examples
on Akka.NET
Arthur Shvetsov 1

2.  Overview and history
 What is an actor model?
 Akka.NET main concepts
 Use-case scenarios
Agenda
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CPU clock speed vs number of cores
CPU clock speed (MHz) # of Cores
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4.  Make classes and functions
 Find areas where you can do multiple things at once
 Queue work onto a new thread or thread pool
 Use synchronization mechanisms to protect shared memory
 Finish work on one thread
 Consume that work on another
How we write multithreaded code?
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6.  Statefulness
 Concurrency
 Recovering from failures
 Bottlenecks
 Availability
Distributed programming pains
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7. Multithreading
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9. - If we don’t want to write multithread code?
- Use concurrency abstractions instead
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10. We won’t talk about TPL today
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11. The Actor Model
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12.  1973 - Concept formulated by Carl Hewitt et al.: “A universal
modular ACTOR formalism for artificial intelligence”
 1986 - Gul Agha, doctoral dissertation "Actors: A Model of
Concurrent Computation in Distributed Systems“
 1986 - Joe Armstrong and others in Ericsson - Erlang programming
language and VM.
 2009 - initial release of Akka framework (JVM, Scala)
 2014.02 - initial release of Akka.NET - Aaron Stannard, Roger
Actor model history
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13.  The Actor Model provides a higher level of abstraction for writing
concurrent and distributed systems.
 Actor Model alleviates the developer from having to deal with explicit
locking and thread management, making it easier to write correct
concurrent and parallel systems.
 Actor Model defines some general rules for how the system’s
components should behave and interact with each other.
What is an actor model?
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14.  No deadlocks
 No shared state
 No global mutable state
 Fault isolation – “let it crash”
 Encapsulation
Actor model benefits
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15.  Akka.NET is a toolkit and runtime for building highly concurrent,
distributed, and fault tolerant event-driven applications on .NET &
Mono.
 Akka.NET is a port of the popular Java/Scala framework Akka to
.NET.
What is Akka.NET?
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16. Everything is an actor!
From OOP to Actor Model paradigm shift
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17. Actor is a code unit organization
What is actor?
OOP Actor
Behavior
State
Synchronous calls
Behavior
State
Asynchronous messages
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18. What is actor?
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19.  All communication is done via message-passing
 All messages are immutable
 Sender and recipient are decoupled, asynchronous
Actors are fundamental units of work & concurrency
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20.  Process messages
 Contain private state, invisible from the outside and changes it upon
reception of a message
 Change behavior between messages (i.e. state machine)
Actors can
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21.  One message processed at a time
 Messages processed in FIFO order
 “At Most Once” delivery guarantied:
 at-most-once delivery
 at-least-once delivery
 exactly-once delivery
Actors promise
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22. Example
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23. Switchable Behaviors
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24. Actor exists as hierarchies
• Parent actors supervise child actors
• Actors are resilient to failures
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25. One-For-One Strategy vs. All-For-One Strategy
Actor supervision
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26.  Communicate with actors through “actor reference”
All actors are identified by a unique address
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27. Actor addresses have location transparency
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29.  Location transparency
 Remote addressing
 Remote messaging
 Remote deployment
Akka.Remote
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30.  Thread
 Instance of an object/component
 Publisher/Subscriber
 Singleton or service (e.g. data access layer)
 State machine
 Load balancer or router
Actor use cases
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31.  http://getakka.net/
 https://github.com/petabridge/akka-bootcamp
References
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32. Thank you!
Arthur Shvetsov
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