Class: RJR::Nodes::WS

Inherits:
RJR::Node show all
Defined in:
lib/rjr/nodes/ws.rb

Overview

Web socket node definition, listen for and invoke json-rpc requests via web sockets

Clients should specify the hostname / port when listening for and invoking requests.

note the RJR javascript client also supports sending / receiving json-rpc messages over web sockets

Examples:

Listening for json-rpc requests over tcp

# initialize node
server = RJR::Nodes::WS.new :node_id => 'server', :host => 'localhost', :port => '7777'

# register rjr dispatchers (see RJR::Dispatcher)
server.dispatcher.handle('hello') do |name|
  "Hello #{name}!"
end

# listen, and block
server.listen
server.join

Invoking json-rpc requests over web sockets using rjr

client = RJR::Nodes::WS.new :node_id => 'client'
puts client.invoke_request('ws://localhost:7777', 'hello', 'mo')

Constant Summary collapse

RJR_NODE_TYPE = 
:ws

Instance Attribute Summary

Attributes inherited from RJR::Node

#dispatcher, #message_headers, #node_id

Instance Method Summary collapse

Methods inherited from RJR::Node

em, #halt, #join, #node_type, #on, tp

Constructor Details

#initialize(args = {}) ⇒ WS

WS initializer

Parameters:

  • args (Hash) (defaults to: {}) —

    the options to create the web socket node with

Options Hash (args):

  • :host (String) —

    the hostname/ip which to listen on

  • :port (Integer) —

    the port which to listen on



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# File 'lib/rjr/nodes/ws.rb', line 87

def initialize(args = {})
   super(args)
   @host      = args[:host]
   @port      = args[:port]

   @connections = []
   @connections_lock = Mutex.new
end

Instance Method Details

#invoke(uri, rpc_method, *args) ⇒ Object

Instructs node to send rpc request, and wait for / return response

Implementation of RJR::Node#invoke

Do not invoke directly from em event loop or callback as will block the message subscription used to receive responses

Parameters:

  • uri (String) —

    location of node to send request to, should be in format of ws://hostname:port

  • rpc_method (String) —

    json-rpc method to invoke on destination

  • args (Array) —

    array of arguments to convert to json and invoke remote method wtih



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# File 'lib/rjr/nodes/ws.rb', line 133

def invoke(uri, rpc_method, *args)
  message = RequestMessage.new :method => rpc_method,
                               :args   => args,
                               :headers => @message_headers

  @@em.schedule {
    init_client(uri) do |c|
      c.stream { |msg| handle_message(msg, c) }

      c.send_msg message.to_s
    end
  }

  # TODO optional timeout for response ?
  result = wait_for_result(message)

  if result.size > 2
    raise Exception, result[2]
  end
  return result[1]
end

#listen ⇒ Object

Instruct Node to start listening for and dispatching rpc requests

Implementation of RJR::Node#listen



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# File 'lib/rjr/nodes/ws.rb', line 110

def listen
  @@em.schedule do
    EventMachine::WebSocket.run(:host => @host, :port => @port) do |ws|
      ws.onopen    { }
      ws.onclose   {       @connection_event_handlers[:closed].each { |h| h.call self } }
      ws.onerror   { |e|   @connection_event_handlers[:error].each  { |h| h.call self } }
      ws.onmessage { |msg| handle_message(msg, ws) }
    end
  end
  self
end

#notify(uri, rpc_method, *args) ⇒ Object

Instructs node to send rpc notification (immadiately returns / no response is generated)

Implementation of RJR::Node#notify

Parameters:

  • uri (String) —

    location of node to send notification to, should be in format of ws://hostname:port

  • rpc_method (String) —

    json-rpc method to invoke on destination

  • args (Array) —

    array of arguments to convert to json and invoke remote method wtih



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# File 'lib/rjr/nodes/ws.rb', line 163

def notify(uri, rpc_method, *args)
  # will block until message is published
  published_l = Mutex.new
  published_c = ConditionVariable.new

  invoked = false
  message = NotificationMessage.new :method => rpc_method,
                                    :args   => args,
                                    :headers => @message_headers
  @@em.schedule {
    init_client(uri) do |c|
      c.stream { |msg| handle_message(msg, c) }

      c.send_msg message.to_s

      # XXX same issue w/ tcp node, due to nature of event machine
      # we aren't guaranteed that message is actually written to socket
      # here, process must be kept alive until data is sent or will be lost
      published_l.synchronize { invoked = true ; published_c.signal }
    end
  }
  published_l.synchronize { published_c.wait published_l unless invoked }
  nil
end

#send_msg(data, ws) ⇒ Object

Send data using specified websocket safely

Implementation of RJR::Node#send_msg



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# File 'lib/rjr/nodes/ws.rb', line 103

def send_msg(data, ws)
  ws.send(data)
end

#to_s ⇒ Object 



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# File 'lib/rjr/nodes/ws.rb', line 96

def to_s
  "RJR::Nodes::WS<#{@node_id},#{@host},#{@port}>"
end