akka akka-cluster akka-platform

How Akka Cluster Works: Actors Living in a Cluster

Hugh McKee Developer Advocate, Lightbend, Inc.

The Code and Behavior of Akka Actors in Akka Cluster

What is an actor in computing? How does it work? How does it recover from failures, communicate across clusters, and represent real-life entities like shopping carts or IoT devices?

In previous How Akka Cluster Works demo projects and videos, we focused on the health of node lifecycles in a cluster, and what happens during node failures and network partitions at the application and infrastructure layers. Now we go a level deeper and look at the code behind Akka actors living in the cluster. We’ll also include a live visualization that you can download and run on your own machine, along with the code provided in the GitHub project. The Akka modules we’ll describe here include Akka Actors, Akka Cluster, and Akka Cluster Sharding.

Project 3 in our series is based on this sample project, and is covered in two parts (both included here). In the first part,

What you’ll learn in these videos:

Part 1
- How actors work throughout a cluster
- How actors balance their workloads across nodes in a cluster
- Code inspection of Actors and messaging styles
Part 2
- What is actor passivation and why is it important for resource consumption
- What happens to actors when nodes fail, how they maintain state
- How actors model real-life entities, e.g. an online shopping cart, or an IoT device like a home smart smoke detector?
- Code inspection of recovery and sharding methods

What you need to get started:

Git
Java 8+
Maven
Sample project: https://github.com/mckeeh3/akka-typed-java-cluster-sharding

Useful links to follow in the videos:

Akka Actors / Introduction to Actors & Actor discovery - https://doc.akka.io/docs/akka/current/typed/actors.html#introduction-to-actors and https://doc.akka.io/docs/akka/current/typed/actor-discovery.html#actor-discovery
Akka Cluster Sharding - https://doc.akka.io/docs/akka/current/typed/cluster-sharding.html#cluster-sharding
Akka Cluster Sharding / Passivation - https://doc.akka.io/docs/akka/current/typed/cluster-sharding.html#passivation
Akka Persistence / Event Sourcing - https://doc.akka.io/docs/akka/current/typed/persistence.html#event-sourcing
Akka Actors / Object-oriented style - https://doc.akka.io/docs/akka/current/typed/actors.html#object-oriented-style

Part 1

Watch on YouTube

Part 2

Watch on YouTube

What's Next?

Learn more with additional "How Akka Works" tutorials:

Using Akka for IoT digital twins: https://www.lightbend.com/blog/iot-building-digital-twins-with-akka-microservices
Webinar on Akka Split Brain Resolver: https://www.lightbend.com/blog/interactive-demo-akka-cluster-nodes-under-attack-visualized
Video / Demo: https://www.lightbend.com/blog/akka-cluster-quickstart-dashboard-part-1-getting-started
Full Project: https://www.lightbend.com/blog/how-to-distribute-application-state-with-akka-cluster-part-1-getting-started

We also invite you to visit the Akka website for in-depth documentation, and if you feel like it's time to explore opportunities with Lightbend, you can schedule a demo for your team:

SCHEDULE A DEMO

Author

Hugh McKee

Developer Advocate, Lightbend, Inc.

Twitter: @mckeeh3

Hugh McKee is a developer advocate at Lightbend. He has had a long career building applications that evolved slowly, that inefficiently utilized their infrastructure, and were brittle and prone to failure. Hugh has learned from his past mistakes, battle scars, and a few wins. And the learning never stops. Now his focus is on helping other developers and architects build resilient, scalable, reactive, distributed systems. Hugh frequently speaks at conferences. He is the author of Designing Reactive Systems: The Role Of Actors In Distributed Architecture (O'Reilly).