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
  @pipe_reader, @pipe_writer = IO.pipe
  @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 82

def method_missing(method_name, *method_params)
  @mutex.synchronize do
    # This flag and loop are used to automatically reconnect and retry if something goes
    # wrong on the first attempt writing to the socket.   Sockets can become disconnected
    # between function calls, but as long as the remote server is back up and running the
    # call should succeed even when it discovers a broken socket on the first attempt.
    first_try = true
    loop do
      raise DRb::DRbConnError, "Shutdown" if @shutdown
      connect() if !@socket or @socket.closed? or @request_in_progress

      response = make_request(method_name, method_params, first_try)
      unless response
        disconnect()
        @socket = nil
        was_first_try = first_try
        first_try = false
        next if was_first_try
      end
      return handle_response(response)
    end # loop
  end # @mutex.synchronize
end

Instance Method Details

#disconnect ⇒ Object

Disconnects from the JSON server



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# File 'lib/cosmos/io/json_drb_object.rb', line 60

def disconnect
  Cosmos.close_socket(@socket)
  @pipe_writer.write('.')
  # Cannot set @socket to nil here because this method can be called by
  # other threads and @socket being nil would cause unexpected errors in method_missing
  # Also don't want to take the mutex so that we can interrupt method_missing if necessary
  # Only method_missing can set @socket to nil
end

#shutdown ⇒ Object

Permanently disconnects from the JSON server



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# File 'lib/cosmos/io/json_drb_object.rb', line 70

def shutdown
  @shutdown = true
  disconnect()
end