What is Akka? - Version 2.4.20

What is Akka?

«resilient elastic distributed real-time transaction processing»

We believe that writing correct distributed, concurrent, fault-tolerant and scalable applications is too hard. Most of the time it's because we are using the wrong tools and the wrong level of abstraction. Akka is here to change that. Using the Actor Model we raise the abstraction level and provide a better platform to build scalable, resilient and responsive applications—see the Reactive Manifesto for more details. For fault-tolerance we adopt the "let it crash" model which the telecom industry has used with great success to build applications that self-heal and systems that never stop. Actors also provide the abstraction for transparent distribution and the basis for truly scalable and fault-tolerant applications.

Akka is Open Source and available under the Apache 2 License.

Download from https://akka.io/downloads.

Please note that all code samples compile, so if you want direct access to the sources, have a look over at the Akka Docs subproject on github: for Java and Scala.

Akka implements a unique hybrid


Actors give you:

  • Simple and high-level abstractions for distribution, concurrency and parallelism.
  • Asynchronous, non-blocking and highly performant message-driven programming model.
  • Very lightweight event-driven processes (several million actors per GB of heap memory).

See the chapter for Scala or Java.

Fault Tolerance

  • Supervisor hierarchies with "let-it-crash" semantics.
  • Actor systems can span over multiple JVMs to provide truly fault-tolerant systems.
  • Excellent for writing highly fault-tolerant systems that self-heal and never stop.

See Fault Tolerance (Scala) and Fault Tolerance (Java).

Location Transparency

Everything in Akka is designed to work in a distributed environment: all interactions of actors use pure message passing and everything is asynchronous.

For an overview of the cluster support see the Java and Scala documentation chapters.


State changes experienced by an actor can optionally be persisted and replayed when the actor is started or restarted. This allows actors to recover their state, even after JVM crashes or when being migrated to another node.

You can find more details in the respective chapter for Java or Scala.

Scala and Java APIs

Akka has both a Scala Documentation and a Java Documentation.

Akka can be used in different ways

Akka is a toolkit, not a framework: you integrate it into your build like any other library without having to follow a particular source code layout. When expressing your systems as collaborating Actors you may feel pushed more towards proper encapsulation of internal state, you may find that there is a natural separation between business logic and inter-component communication.

Akka applications are typically deployed as follows:

Commercial Support

Akka is available from Lightbend Inc. under a commercial license which includes development or production support, read more here.