93 lines
3.4 KiB
ReStructuredText
93 lines
3.4 KiB
ReStructuredText
.. _what-is-akka:
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###############
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What is Akka?
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###############
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**Scalable real-time transaction processing**
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We believe that writing correct concurrent, fault-tolerant and scalable
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applications is too hard. Most of the time it's because we are using the wrong
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tools and the wrong level of abstraction. Akka is here to change that. Using
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the Actor Model we raise the abstraction level and provide a better platform to
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build scalable, resilient and responsive applications—see the `Reactive
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Manifesto <http://reactivemanifesto.org/>`_ for more details. For
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fault-tolerance we adopt the "let it crash" model which the telecom industry
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has used with great success to build applications that self-heal and systems
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that never stop. Actors also provide the abstraction for transparent
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distribution and the basis for truly scalable and fault-tolerant applications.
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Akka is Open Source and available under the Apache 2 License.
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Download from http://akka.io/downloads.
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Please note that all code samples compile, so if you want direct access to the sources, have a look
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over at the Akka Docs subproject on github: for `Java <@github@/akka-docs/rst/java/code/docs>`_
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and `Scala <@github@/akka-docs/rst/scala/code/docs>`_.
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Akka implements a unique hybrid
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===============================
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Actors
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------
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Actors give you:
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- Simple and high-level abstractions for concurrency and parallelism.
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- Asynchronous, non-blocking and highly performant event-driven programming model.
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- Very lightweight event-driven processes (several million actors per GB of heap memory).
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See the chapter for :ref:`Scala <actors-scala>` or :ref:`Java <untyped-actors-java>`.
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Fault Tolerance
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---------------
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- Supervisor hierarchies with "let-it-crash" semantics.
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- Supervisor hierarchies can span over multiple JVMs to provide truly fault-tolerant systems.
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- Excellent for writing highly fault-tolerant systems that self-heal and never stop.
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See :ref:`Fault Tolerance (Scala) <fault-tolerance-scala>` and :ref:`Fault Tolerance (Java) <fault-tolerance-java>`.
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Location Transparency
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---------------------
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Everything in Akka is designed to work in a distributed environment: all
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interactions of actors use pure message passing and everything is asynchronous.
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For an overview of the cluster support see the :ref:`Java <cluster_usage_java>`
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and :ref:`Scala <cluster_usage_scala>` documentation chapters.
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Persistence
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-----------
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Messages received by an actor can optionally be persisted and replayed when the actor is started or
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restarted. This allows actors to recover their state, even after JVM crashes or when being migrated
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to another node.
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You can find more details in the respective chapter for :ref:`Java <persistence-java>` or :ref:`Scala <persistence-scala>`.
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Scala and Java APIs
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===================
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Akka has both a :ref:`scala-api` and a :ref:`java-api`.
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Akka can be used in two different ways
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======================================
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Akka can be used and deployed in different ways:
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- As a library: used as a regular JAR on the classpath and/or in a web app, to
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be put into ``WEB-INF/lib``
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- Package with `sbt-native-packager <https://github.com/sbt/sbt-native-packager>`_
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- Package and deploy using `Typesafe ConductR <http://typesafe.com/products/conductr>`_.
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Commercial Support
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==================
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Akka is available from Typesafe Inc. under a commercial license which includes
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development or production support, read more `here
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<http://www.typesafe.com/how/subscription>`_.
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