http_replicator.rb

require 'rubygems'
require 'eventmachine'
require 'evma_httpserver'
require 'event_utils'
require 'singleton'
require 'syslog'
require 'trollop'
require 'yaml'

class Syslogger
  include Singleton
  def initialize
    @s = Syslog.open('http_duplicator', Syslog::LOG_PID, Syslog::LOG_DAEMON)
    @s.info("Started logger for http duplicator")
  end

  def debug(msg)
    @s.debug msg
    puts "DEBUG #{msg}" if $DEBUG
  end
  def info(msg)
    @s.info msg
    puts "INFO #{msg}"
  end
end

class Backend
  attr_reader :host, :port, :status, :headers, :content

  include EM::Deferrable

  def initialize(host, port, is_master=false)
    @host = host
    @port = port
    @is_master = false
  end

  def send_request(params)

    client = EventMachine::Protocols::HttpClient.request(params)

    client.callback {|response|
      @status = response[:status]
      @headers = response[:headers]
      @content = response[:content]
      self.succeed
    }

    client.errback do
      Syslogger.instance.info("Unable to perform request #{params[:host]}:#{params[:port]}#{params[:request]}.")
      @status = nil
    end
    return self
  end
end

class MasterSlaveConfiguration
  include Singleton
  attr_reader :members
  attr_reader :listen_port
  attr_accessor :filename
  DEFAULT_CONFIGURATION = %Q|
---
master:
- www.virtual.ftnz.net
- 2002
slave:
- www.virtual.ftnz.net
- 2002
|
  def initialize
    @members = {}
    @old_conf = nil
  end
  def refresh

    if not File.exists?(@filename)
      Syslogger.instance.info("#{@filename} not found, using default configuration.")
      conf = YAML.load(DEFAULT_CONFIGURATION)
    else
      conf = YAML.load(File.open(@filename).read)
      if  @old_conf != conf
       Syslogger.instance.info("Loaded configuration #{@filename}, with configuration #{conf.inspect}.")
      end
    end

    @listen_port = conf['listen_port']
    @members[:master] = conf['master']
    @members[:slave] = conf['slave']

    if @old_conf != conf
       @load_time = Time.now
    end

    @old_conf = conf
  end
  def master
    reload_if_needed
    @members[:master]
  end
  def slave
    reload_if_needed
    @members[:slave]
  end
  def reload_if_needed
    if Time.now - @load_time > 10
      refresh
    end
  end
end

class HTTP_Duplicator < EM::Connection
  include EM::HttpServer
  include EventUtils

  def post_init
    super
    no_environment_strings
    master = MasterSlaveConfiguration.instance.master
    @master = Backend.new(master[0], master[1])

    slave =  MasterSlaveConfiguration.instance.slave
    @slave = Backend.new(slave[0], slave[1])
  end

  def process_http_request
    Syslogger.instance.debug("Processing #{@http_request_method} #{@http_request_uri}.")
    in_deferred_loop do
      master = @master.send_request(
        :host => @master.host,
        :port => @master.port,
        :request => @http_request_uri,
        :verb => @http_request_method,
        :content => @http_post_content,
        :contenttype => @http_content_type,
        :querystring => @http_query_string
      )
      # Only forward GETS to the slave, ignore the other methods
      if @slave.host != nil && @http_request_method == 'GET'
        slave = @slave.send_request(
          :host => @slave.host,
          :port => @slave.port,
          :request => @http_request_uri,
          :verb => @http_request_method,
          :content => @http_post_content,
          :contenttype => @http_content_type,
          :querystring => @http_query_string
        )
      end

    waiting_for(master) do
      response = EM::DelegatedHttpResponse.new(self)

      response.status = master.status.to_i
      response.content = master.content
#      response.headers = master.headers.delete("Content-length")
      
      response.send_response
    end
    waiting_for(slave) do
      if slave.status != 200
        Syslogger.instance.info "Something went wrong on the slave: "+slave.status.inspect
      end
    end
    end
  end
end



opts = Trollop::options do
  opt :configuration_file, "configuration file", :default => "replicator.yml"
  opt :port, "Listening port", :default => 10080
end
MasterSlaveConfiguration.instance.filename = opts[:configuration_file]
MasterSlaveConfiguration.instance.refresh

EM::run do
  EM::start_server '0.0.0.0', opts[:port], HTTP_Duplicator
end