9bc01ae265
The idea is to filter the sources, replacing @<var>@ occurrences with the mapping for <var> (which is currently hard-coded). @@ -> @. In order to make this work, I had to move the doc sources one directory down (into akka-docs/rst) so that the filtered result could be in a sibling directory so that relative links (to _sphinx plugins or real code) would continue to work. While I was at it I also changed it so that WARNINGs and ERRORs are not swallowed into the debug dump anymore but printed at [warn] level (minimum). One piece of fallout is that the (online) html build is now run after the normal one, not in parallel.
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.. _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 the
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Actor Model we raise the abstraction level and provide a better platform to build
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correct, concurrent, and scalable applications. For fault-tolerance we adopt the
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"Let it crash" model which the telecom industry has used with great success to
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build applications that self-heal and systems that never stop. Actors also provide
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the abstraction for transparent distribution and the basis for truly scalable and
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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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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 (approximately 2.7 million actors per GB RAM).
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See :ref:`actors-scala` and :ref:`untyped-actors-java`
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Fault Tolerance
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---------------
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Fault tolerance through supervisor hierarchies with "let-it-crash"
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semantics. Excellent for writing highly fault-tolerant systems that never stop,
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systems that self-heal. Supervisor hierarchies can span over multiple JVMs to
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provide truly fault-tolerant systems.
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See :ref:`fault-tolerance-scala` and :ref:`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 purely message passing and everything is asynchronous.
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For an overview of the remoting see :ref:`remoting`
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Transactors
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-----------
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Transactors combine actors and STM (Software Transactional Memory) into transactional actors.
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It allows you to compose atomic message flows with automatic retry and rollback.
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See :ref:`transactors-scala` and :ref:`transactors-java`
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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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- As a library: used by a web app, to be put into ``WEB-INF/lib`` or as a regular
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JAR on your classpath.
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- As a microkernel: stand-alone kernel to drop your application into.
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See the :ref:`deployment-scenarios` for details.
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What happened to Cloudy Akka?
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=============================
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The commercial offering was earlier referred to as Cloudy Akka. This offering
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consisted of two things:
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- Cluster support for Akka
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- Monitoring & Management (formerly called Atmos)
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Cloudy Akka have been discontinued and the Cluster support is now being moved into the
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Open Source version of Akka (the upcoming Akka 2.1), while the Monitoring & Management
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(Atmos) is now rebranded into Typesafe Console and is part of the commercial subscription
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for the Typesafe Stack (see below for details).
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Typesafe Stack
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==============
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Akka is now also part of the `Typesafe Stack <http://typesafe.com/stack>`_.
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The Typesafe Stack is a modern software platform that makes it easy for developers
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to build scalable software applications. It combines the Scala programming language,
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Akka, the Play! web framework and robust developer tools in a simple package that
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integrates seamlessly with existing Java infrastructure.
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The Typesafe Stack is all fully open source.
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Typesafe Console
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================
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On top of the Typesafe Stack we also have a commercial product called Typesafe
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Console which provides the following features:
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#. Slick Web UI with real-time view into the system
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#. Management through Dashboard, JMX and REST
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#. Dapper-style tracing of messages across components and remote nodes
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#. Real-time statistics
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#. Very low overhead monitoring agents (should always be on in production)
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#. Consolidation of statistics and logging information to a single node
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#. Storage of statistics data for later processing
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#. Provisioning and rolling upgrades
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Read more `here <http://typesafe.com/products/typesafe-subscription>`_.
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