make all net/http requests go through an http proxy

net_http_default_proxy.rb

require 'net/http'

module Net
  module DefaultProxy
    # Defaults all requests through Net::HTTP through an http proxy.
    # Example:
    #   require 'net/http'
    #   require 'net/http_extensions'
    #   Net::HTTP.set_http_proxy!
    #
    # @param options [Hash] proxy options. 
    #   Defaults to parsed values of ENV['http_proxy'] or ENV['HTTP_PROXY']
    #   :host
    #   :port [Integer]
    #   :user
    #   :password
    def set_http_proxy!(options = {})
      require 'addressable/uri'
      proxy_uri = if options.empty?
        Addressable::URI.parse(ENV['HTTP_PROXY'] || ENV['http_proxy'])
      else
        require 'ostruct'
        OpenStruct.new(options)
      end

      self.class_eval <<-CODE
        class << self
          alias_method :old_new, :new
          def new(address, port = nil, p_addr = '#{proxy_uri.host}', p_port = #{proxy_uri.port}, p_user = '#{proxy_uri.user}', p_pass = '#{proxy_uri.password}')
            old_new(address, port, p_addr, p_port, p_user, p_pass)
          end
        end
      CODE
    end

    # restore normal net/http behavior
    def unset_http_proxy!
      self.class_eval <<-CODE
        class << self
          alias_method :new, :old_new
        end
      CODE
    end
  end
end

Net::HTTP.extend(Net::DefaultProxy)