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https://github.com/tarcieri/cool.io

Simple evented I/O for Ruby (but please check out Celluloid::IO instead)
https://github.com/tarcieri/cool.io

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Simple evented I/O for Ruby (but please check out Celluloid::IO instead)

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README 

        
Cool.io

=======



Cool.io is an event library for Ruby, built on the libev event library which 

provides a cross-platform interface to high performance system calls .  This 

includes the epoll system call for Linux, the kqueue system call for BSDs and 

OS X, and the completion ports interface for Solaris.



Cool.io also binds asynchronous wrappers to Ruby's core socket classes so you can

use them in conjunction with Cool.io to build asynchronous event-driven 

applications.



You can include Cool.io in your programs with:



```ruby

require 'cool.io'

```



Anatomy

-------



Cool.io builds on two core classes which bind to the libev API:



* Cool.io::Loop - This class represents an event loop which uses underlying high

  performance system calls to wait for events.



* Cool.io::Watcher - This is the base class for event observers.  Once you attach

  an event observer to a loop and start running it, you will begin receiving

  callbacks to particlar methods when events occur.



Watchers

--------



There are presently four types of watchers:



* Cool.io::IOWatcher - This class waits for an IO object to become readable,

  writable, or both.



* Cool.io::TimerWatcher - This class waits for a specified duration then fires

  an event.  You can also configure it to fire an event at specified intervals.



* Cool.io::StatWatcher - Monitors files or directories for changes



* Cool.io::AsyncWatcher - Can be used to wake up a Cool.io::Loop running in a

  different thread. This allows each thread to run a separate Cool.io::Loop and

  for the different event loops to be able to signal each other.



Using Watchers

--------------



Watchers have five important methods:



* attach(loop) - This binds a watcher to the specified event loop.  If the

  watcher is already bound to a loop it will be detached first, then attached

  to the new one.



* detach - This completely unbinds a watcher from an event loop.



* disable - This stops the watcher from receiving events but does not unbind

  it from the loop.  If you are trying to toggle a watcher on and off, it's

  best to use this method (and enable) as it performs better than completely

  removing the watcher from the event loop.



* enable - This re-enables a watcher which has been disabled in the past.

  The watcher must still be bound to an event loop.



* evloop - This returns the Cool.io::Loop object which the watcher is currently

  bound to.



Asynchronous Wrappers

---------------------



Several classes which provide asynchronous event-driven wrappers for Ruby's

core socket classes are also provided.  Among these are:



* Cool.io::TCPSocket - A buffered wrapper to core Ruby's Socket class for use with

  TCP sockets.  You can asynchronously create outgoing TCP connections using 

  its Cool.io::TCPSocket.connect method.  Cool.io::TCPSocket provides write buffering

  to ensure that writing never blocks, and has asynchronous callbacks for

  several events, including when the connection is opened (or failed), when

  data is received, when the write buffer has been written out completely,

  and when the connection closes.



* Cool.io::TCPServer - A wrapper for TCPServer which creates new instances of

  Cool.io::TCPSocket (or any subclass you wish to provide) whenever an incoming

  connection is received.



Example Program

---------------



Cool.io provides a Sinatra-like DSL for authoring event-driven programs:



```ruby

require 'cool.io'

require 'cool.io/dsl'



ADDR = '127.0.0.1'

PORT = 4321



cool.io.connection :echo_server_connection do

  on_connect do

    puts "#{remote_addr}:#{remote_port} connected"

  end



  on_close do

    puts "#{remote_addr}:#{remote_port} disconnected"

  end



  on_read do |data|

    write data

  end

end



puts "Echo server listening on #{ADDR}:#{PORT}"

cool.io.server ADDR, PORT, :echo_server_connection

cool.io.run

```

    

This creates a new connection class called :echo_server_connection and defines

a set of callbacks for when various events occur.



We then create a new server on the given address and port. When this server

receives new connections, it will create new instances of the given connection

class for each connection.



Finally, we kick everything off with cool.io.run. Calling cool.io.run will 

block, listening for events on our server.

    

Using Cool.io subclasses directly

---------------------------------



Below is an example of how to write an echo server using a subclass instead of

the DSL:



```ruby

require 'cool.io'

HOST = 'localhost'

PORT = 4321



class EchoServerConnection < Cool.io::TCPSocket

  def on_connect

    puts "#{remote_addr}:#{remote_port} connected"

  end



  def on_close

    puts "#{remote_addr}:#{remote_port} disconnected"

  end



  def on_read(data)

    write data

  end

end



server = Cool.io::TCPServer.new(HOST, PORT, EchoServerConnection)

server.attach(Cool.io::Loop.default)



puts "Echo server listening on #{HOST}:#{PORT}"

Cool.io::Loop.default.run

```



Here a new observer type (EchoServerConnection) is made by subclassing an

existing one and adding new implementations to existing event handlers.



A new event loop is created, and a new Cool.io::TCPServer (whose base class is

Cool.io::Watcher) is created and attached to the event loop.



Once this is done, the event loop is started with event_loop.run.  This method

will block until there are no active watchers for the loop or the loop is

stopped explicitly with event_loop.stop.