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anode

Humus inspired actor framework for Node.js

Stability: 0 - Deprecated -- For an improved way of expressing actors in Node.js see Tiny Actor Run-Time

Installation

Installing node

Follow instructions at http://nodejs.org/

Installing npm (node package manager)

  curl http://npmjs.org/install.sh | sh

Installing anode

  npm install anode

Actors

The intent behind anode is to provide a way to write "pure" actors in JavaScript. Over the years, the idea of what actors are has evolved quite a bit. In the context of what anode is trying to provide, "pure" actors are actors as defined by Carl Hewitt and elaborated by Gul Agha. Dale Schumacher (the author of pure actor language Humus on which anode is inspired) provides an excellent introduction to this perspective on actors on his blog here.

tl;dr

Actor processing starts on receipt of a message. In response to a message, an actor can do three things:

  1. send a finite number of new messages (@send)
  2. create a finite number of new actors (@create)
  3. designate a new behavior to process subsequent messages (@become)

Getting Started

A quick note about CoffeeScript... Because of how anode actors are implemented, the code relies heavily on the this keyword. There is nothing preventing you from writing anode actors in JavaScript, however, the CoffeeScript syntax just happens to perfectly fit what each actor behavior is trying to express, so I highly recommend taking look at anode through the CoffeeScript lens.

http webserver

Taking a pointer from Node.js, here is an example webserver in anode included in examples/helloworld.example.coffee

anode = require 'anode'

cnf = new anode.Configuration()

httpServer = cnf.actor anode.http.server_beh()
helloworld = cnf.actor anode.behavior( 'httpServer'

  '#start' : ->
    @send( @, '#listen', 8080, '127.0.0.1' ).to @httpServer

  '$httpServer, #listen' : ->
    @send( 'Server running at http://127.0.0.1:8080/' ).to cnf.console.log

  '$httpServer, #request, request, response' : ->
    @send( null, '#end', 'Hello Actor World\n' ).to @response  

)( httpServer ) # helloworld

cnf.send( '#start' ).to helloworld

To run the server, go into the examples directory and execute it with coffee:

% coffee helloworld.example.coffee
Server running at http://127.0.0.1:8080/

*note: not all of the Node.js 'http' functionality has been wrapped yet.

socket server

A more involved echo server using sockets directly can be found in examples/echoserver.example.coffee

anode = require 'anode'

# set debug mode to see the messages
cnf = new anode.Configuration debug : true

# we are naming our actors here to make debug output friendlier
netServer = cnf.actor 'netServer', anode.net.server_beh()
echoServer = cnf.actor 'echoServer', anode.beh( 'netServer'

  '#start' : ->

    @send( @, '#listen', 8124 ).to @netServer

  # response from netServer acknowledging that it is listening and ready
  '$netServer, #listen' : ->

    @send( 'server bound' ).to cnf.console.log

  # message from netServer when it receives a new connection
  '$netServer, #connection, socket' : ->

    @send( 'server connected' ).to cnf.console.log

    # request ack after #write completes by including self (@)
    @send( @, '#write', 'hello\r\n' ).to @socket

  'socket, #end' : ->

    @send( 'server disconnected' ).to cnf.console.log

  # once socket gives us its socket object
  'socket, #socket, socketObj' : ->
  
    # pipe the socket to itself to echo
    # don't care about confirmation so send null as customer
    @send( null, '#pipe', @socketObj ).to @socket

  # write ack
  'socket, #write, _' : ->

    # request the actual socket object so we can pipe to it
    @send( @, '#socket' ).to @socket

)( netServer ) # echoServer

cnf.send( '#start' ).to echoServer

To run the server, go into the examples directory and execute it with coffee:

% coffee echoserver.example.coffee
FROM [configuration] TO [echoServer::10] SEND [ '#start' ]
FROM [echoServer::10] TO [netServer::9] SEND [ '[echoServer::10]', '#listen', '8124' ]
FROM [netServer::9] TO [echoServer::10] SEND [ '[netServer::9]', '#listen' ]
FROM [echoServer::10] TO [console.log::1] SEND [ 'server bound' ]
server bound

You can connect to it using telnet:

% telnet localhost 8124

More Examples

I've begun a tutorial to demonstrate some of the elementary concepts of coding actors in anode. It is documented in code in examples/tutorial/one.coffee.

Take a look at the examples in the examples folder. As of this writing, there are three non-trivial examples of setting up an actor configuration:

  1. erlangMailbox.coffee is an implementation of Erlang-style mailbox modeled on Dale's blog post, run coffee erlangMailbox.example.coffee
  2. lambda1.coffee is an implementation of lambda calculus modeled on Dale's blog post, run coffee lambda1.example.coffee (you should see 42)
  3. lambda2.coffee is a follow-on implementation of lambda calculus modeled on the second blog post in that series, run coffee lambda2.example.coffee (you should see true and false)

Other examples show simpler functionality:

  1. console.warn.example.coffee demonstrates actor wrappers around node.js console, run coffee console.warn.example.coffee
  2. valuematch.example.coffee shows how $ syntax matches pattern by evaluating the variable, run coffee valuematch.example.coffee
  3. simple.example.coffee shows a simple counter system, run coffee simple.example.coffee
  4. optional.example.coffee shows use of optional parameters in a message, run coffee optional.example.coffee
  5. assert.example.coffee shows the use of assertions as well as demonstrating the anode message "stack trace" in case an unexpected error occurs, run coffee assert.example.coffee

License

(The MIT License)

Copyright (c) 2011 Tristan Slominski

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.