Introduction to Akka Actors

with Java 8

Mememememememememe

Instead of more Ghz more cores

source: http://queue.acm.org/detail.cfm?id=2181798

Another thing that has changed

Build powerful concurrent & distributed applications more easily.

Akka is a toolkit and runtime for building highly concurrent, distributed, and resilient message-driven applications on the JVM

”The actor model in computer science is a mathematical model of concurrent computation that treats actors as the universal primitives of concurrent computation. ”

Wikipedia

The Actor Model

An Actor

and acts on them by: • Sending messages • Changing its state • Changing its behavior • Creating more actors

receives messages

The Actor hierarchy/user

system.actorOf(props, ”my-actor”)

/user/my-actor

getContext() .actorOf(…, ”my-child”)

/user/my-actor/my-child

Supervision/user

/user/my-actor

🌋

Actor Lifecycle

actorOf()

New instance -

restarted

restart

resume

stop

ActorRef

Dispatch (Actor Execution)Actor-a

Actor-b

Thread 1

Thread 2

b

b

ba a

a

Time

BlockingActor-a

Actor-b

Thread 1

Thread 2

b b

a

Time

a

Actor-c

Dos and don’tsDon’t: Put every actor under /userSeparate parts using supervisors so they can fail independently Do: Isolate blocking Put blocking logic on its own thread based dispatcher Don’t: Write all your logic inside your actorsMake what is possible ”regular” OO logic that you can set up and unit test synchronously

Do: Make all messages immutable Or else there will be concurrency/visibility problems

Do: Put asynchronous boundaries where it makes sense Three tier where each tier is an actor is probably not that useful

What more is there?

Akka Cluster

Akka Streams

and cluster tools

async & back-pressured

Get startedLearn more - the docs: http://akka.io/docs

Get help: gitter channel: https://gitter.im/akka/akka mailing list: https://groups.google.com/forum/#!forum/akka-user

Project with samples: https://github.com/johanandren/akka-actor-java8-webinar