actors drammen

Actors

Drammen

25.10.2012

Reidar Sollid

The actor programming model

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Erlang

• The world is concurrent

• Things in the world don't share data

• Things communicate with messages

• Things fail

• - Joe Armstrong

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Original problem

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New problem

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Shared memory

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Shared memory model

Shared memory

Processthread

Processthread

Processthread

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Concurrency and shared memory

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What is the Actor Model

• Light weight processes/tasks/agents communicating through messaging

• Messages are buffered in a “mailbox”

• No shared state

• Isolated from other processes

• Normally event systems are inversion of control

• Adding a listener to an object

• Hard to maintain in large systems

• Humans do not share memory, we communicate through messages

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React or receive

• React is the “normal” actor, lightweight process

• Receive spins out a new Java thread

• In the paper *

• 5000 threads

• 1 200 000 actors

• React uses partial functions to send the process to the heap

• Receive runs on the stack and is heavyweight JVM threads (like Java)

• *Actors That Unify Threads and Events P. Haller, M. Odersky

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Pattern matching

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Pattern matching

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Tail optimized recursion

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Tail recursion

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F# Agent

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Scala actor

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Application security

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