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, connect_timeout = 1.0) ⇒ 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, connect_timeout = 1.0)
  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
  @connect_timeout = connect_timeout
  @connect_timeout = @connect_timeout.to_f if @connect_timeout
  @shutdown = 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 76

def method_missing(method_name, *method_params)
  @mutex.synchronize do
    raise DRb::DRbConnError, "Shutdown" if @shutdown
    if !@socket or @socket.closed? or @request_in_progress
      if @request_in_progress
        disconnect()
        @socket = nil
        @request_in_progress = false
      end
      begin
        addr = Socket.pack_sockaddr_in(@port, @hostname)
        @socket = Socket.new(Socket::AF_INET, Socket::SOCK_STREAM, 0)
        @socket.setsockopt(Socket::IPPROTO_TCP, Socket::TCP_NODELAY, 1)
        begin
          @socket.connect_nonblock(addr)
        rescue IO::WaitWritable
          begin
            _, sockets, _ = IO.select(nil, [@socket], nil, @connect_timeout) # wait 3-way handshake completion
          rescue IOError, Errno::ENOTSOCK
            disconnect()
            @socket = nil
            raise "Connect canceled"
          end
          if sockets and !sockets.empty?
            begin
              @socket.connect_nonblock(addr) # check connection failure
            rescue IOError, Errno::ENOTSOCK
              disconnect()
              @socket = nil
              raise "Connect canceled"
            rescue Errno::EINPROGRESS
              retry
            rescue Errno::EISCONN, Errno::EALREADY
            end
          else
            disconnect()
            @socket = nil
            raise "Connect timeout"
          end
        rescue IOError, Errno::ENOTSOCK
          disconnect()
          @socket = nil
          raise "Connect canceled"
        end
      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
      disconnect()
      @socket = nil
      raise DRb::DRbConnError, e.message, e.backtrace
    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
      disconnect()
      @socket = nil
      raise DRb::DRbConnError, "Socket closed by server"
    end
  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 59

def disconnect
  Cosmos.close_socket(@socket)
end

#shutdown ⇒ Object

Permanently disconnects from the JSON server



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# File 'lib/cosmos/io/json_drb_object.rb', line 64

def shutdown
  @shutdown = true
  disconnect()
end