# Concurrency Without the Pain: Introduction to Akka.NET and the Actor Model The .NET platform's most recent major releases prominently feature improved concurrency tools and keywords, and that's no accident. In a world where developers are expected to build applications that are consistently responsive across a wide range of devices, user experiences, and workloads knowing how to take full advantage of the power of concurrent programming is essential. But let's face it: even with nice tools like the TPL and async / await, multi-threaded concurrent programming has typically been a bottomless pit of despair, Heisenbugs, and lessons learned the hard way. None of this is true with Akka.NET and the actor model: a powerful programming methodology that makes building concurrent applications easy, fun, and much more powerful than what we had before.

1. Akka.NET: Concurrency without
the Pain
By Aaron Stannard,
Founder, Akka.NET
CEO, Petabridge

2. Modern CPUs: More Cores!
Source: Karl Rupp https://www.karlrupp.net/2018/02/42-years-of-microprocessor-trend-data/

3. Modern Software: Concurrent
• Can’t take advantage of multi-core
architectures without multi-threaded or
multi-process (concurrent) application
designs
• Industry best practices increasingly push
language and API designs to drive this:
– Task and Parallelism Library (TPL)
– Async / Await
– More native async APIs in standard and third
party libraries

4. Concurrent Programming is
Hard

5. How to Write Concurrent
Software

6. Shared State is Tricky

7. Enter the Actor Model

8. Actor Model Origins
• Originally conceived in
1973 to build large, multi-
core applications.
• First implemented in 1986
by Ericsson. Powers
modern day GPRS, 3G,
and LTE cell networks.
• Later adopted by Internet
giants.
• Made popular again by
cloud computing.

9. Actor Model Core Concepts

10. What is an Actor?

11. Actors
• Actors are independent micro-processes.
• They are cheap, disposable, units of work.
• Each has its own state and resources that
can’t be shared or directly accessed from
the outside.
• They work by sending and processing
immutable messages to each other.

12. Actors Process One
Message at a Time

13. Processes Usually Contain
Many Actors

14. Parent Actors Supervise
Children

15. How Actors Make Concurrent
Programming Easier
• Since actor state is private and can only be modified
serially, it’s automatically thread-safe
– No locks, critical regions, or synchronization
mechanisms needed
• Actors process messages asynchronously
– Lots of actors can process messages simultaneously
– Scale up to take advantage of multiple CPUs
automatically
• Robust fault-handling model
– Parents supervise child failures
– Faults isolated to failing actor only
– Actor restarts are transparent and “not a big deal”

16. Akka.NET: Actor Model for .NET

17. Actor Syntax

18. IActorRef – Actor References

21. Actor References are
Location Transparent
• IActorRef can point to
local actor (in-
memory messaging.)
• IActorRef can point to
actor running in
another remote
process (TCP
messaging.)
• You don’t need to
explicitly know or care
which is which.

22. But Actors Still
Have Explicit Addresses

23. Demo
Akka.Remote Chat Example
https://github.com/akkadotnet/akka.net

24. Akka.NET Modules
• Akka – core actor library
• Akka.Remote – cross-node actor deployment /
communication
• Akka.Cluster – elastic actor networks (HA)
• Akka.Persistence – event-sourcing, durable actor state &
recovery
• Akka.Streams – streaming workflows
• Akka.Cluster.Tools – cluster singleton, distributed pub
sub
• Akka.Cluster.Sharding – durable state partitioning
• Akka.DData – eventually consistent data replication

25. When to Use Actors (Generally)
• Building stateful applications:
– Applications that can’t be built reliably using a
database as the sole source of truth.
– Examples: real-time applications, IOT, trading,
monitoring, marketing automation, large-scale
data analysis.
• Building highly fault-tolerant applications.
• Just need better concurrency tools in non-
distributed applications.

26. Where to Learn More
• http://learnakka.net – Akka.NET bootcamp
• http://getakka.net/ - Official website
• https://petabridge.com/ - Blog and tutorials