Class: Cosmos::JsonDRbObject

Inherits:
Object
  • Object
show all
Defined in:
lib/cosmos/io/json_drb_object.rb

Overview

Used to forward all method calls to the remote server object. Before using this class ensure the remote service has been started in the server class:

json = JsonDrb.new
json.start_service('127.0.0.1', 7777, self)

Now the JsonDRbObject can be used to call server methods directly:

server = JsonDRbObject('127.0.0.1', 7777)
server.cmd(*args)

Instance Method Summary collapse

Constructor Details

#initialize(hostname, port) ⇒ JsonDRbObject

Returns a new instance of JsonDRbObject.

Parameters:

  • hostname (String) —

    The name of the machine which has started the JSON service

  • port (Integer) —

    The port number of the JSON service



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# File 'lib/cosmos/io/json_drb_object.rb', line 36

def initialize(hostname, port)
  hostname = '127.0.0.1' if (hostname.to_s.upcase == 'LOCALHOST')
  begin
    @addr = Socket.pack_sockaddr_in(port, hostname)
  rescue => error
    if error.message =~ /getaddrinfo/
      raise "Invalid hostname: #{hostname}"
    else
      raise error
    end
  end
  @hostname = hostname
  @port = port
  @mutex = Mutex.new
  @socket = nil
  @id = 0
  @request_in_progress = false
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(method_name, *method_params) ⇒ Object

Forwards all method calls to the remote service.

Parameters:

  • method_name (Symbol) —

    Name of the method to call

  • method_params (Array) —

    Array of parameters to pass to the method

Returns:

  • The result of the method call. If the method raises an exception the same exception is also raised. If something goes wrong with the protocol a DRb::DRbConnError exception is raised.



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# File 'lib/cosmos/io/json_drb_object.rb', line 67

def method_missing(method_name, *method_params)
  @mutex.synchronize do
    first_try = true
    loop do
      if !@socket or @socket.closed? or @request_in_progress
        if @request_in_progress
          @socket.close if @socket and !@socket.closed?
          @socket = nil
          @request_in_progress = false
        end
        begin
          @socket = TCPSocket.new(@hostname, @port)
          @socket.setsockopt(Socket::IPPROTO_TCP, Socket::TCP_NODELAY, 1)
        rescue => e
          raise DRb::DRbConnError, e.message
        end
      end

      request = JsonRpcRequest.new(method_name, method_params, @id)
      @id += 1

      request_data = request.to_json(:allow_nan => true)
      begin
        @request_in_progress = true
        STDOUT.puts "Request:\n" if JsonDRb.debug?
        STDOUT.puts request_data if JsonDRb.debug?
        JsonDRb.send_data(@socket, request_data)
        response_data = JsonDRb.receive_message(@socket, '')
        STDOUT.puts "\nResponse:\n" if JsonDRb.debug?
        STDOUT.puts response_data if JsonDRb.debug?
        @request_in_progress = false
      rescue => e
        @socket.close if @socket and !@socket.closed?
        @socket = nil
        if first_try
          first_try = false
          next
        else
          raise DRb::DRbConnError, e.message, e.backtrace
        end
      end

      if response_data
        response = JsonRpcResponse.from_json(response_data)
        if JsonRpcErrorResponse === response
          if response.error.data
            raise Exception.from_hash(response.error.data)
          else
            raise "JsonDRb Error (#{response.error.code}): #{response.error.message}"
          end
        else
          return response.result
        end
      else
        # Socket was closed by server
        @socket.close if @socket and !@socket.closed?
        @socket = nil
        if first_try
          first_try = false
          next
        else
          # Socket already closed by receive_message
          raise DRb::DRbConnError, "Socket closed by server"
        end
      end
    end # loop
  end
end

Instance Method Details

#disconnect ⇒ Object

Disconnects from the JSON server



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# File 'lib/cosmos/io/json_drb_object.rb', line 56

def disconnect
  @socket.close if @socket and !@socket.closed?
end