RJR - Ruby Json Rpc Library

Copyright (C) 2012-2013 Mo Morsi mo@morsi.org

RJR is made available under the Apache License, Version 2.0

RJR is an implementation of the JSON-RPC Version 2.0 Specification. It allows a developer to register custom JSON-RPC method handlers which may be invoked simultaneously over a variety of transport mechanisms.

Currently supported transports include: tcp, amqp, http (post), websockets, local method calls, (others coming soon)

Note some transports require additional dependencies, see rjr.gemspec for more info.

Intro

RJR is currently built ontop of eventmachine and json, any dependencies of those are needed to run rjr.

To install rjr simply run: gem install rjr

Source code is available via: git clone http://github.com/movitto/rjr

Using

Simply require the transports which you would like to use:

    require 'rjr/nodes/tcp'
    require 'rjr/nodes/amqp'
    require 'rjr/nodes/ws'
    require 'rjr/nodes/web'
    require 'rjr/nodes/local'
    require 'rjr/nodes/multi'

server.rb:

    # listen for methods via amqp, websockets, http, and via local calls
    amqp_node  = RJR::Nodes::AMQP.new  :node_id => 'server', :broker => 'localhost'
    ws_node    = RJR::Nodes::WS.new    :node_id => 'server', :host   => 'localhost', :port => 8080
    www_node   = RJR::Nodes::Web.new   :node_id => 'server', :host   => 'localhost', :port => 8888
    local_node = RJR::Nodes::Local.new :node_id => 'server'
    multi_node = RJR::Nodes::Multi.new :nodes => [amqp_node, ws_node, www_node, local_node]

    # define a rpc method called 'hello' which takes
    # one argument and returns it in upper case
    multi_node.dispatcher.handle("hello") { |arg|
      arg.upcase
    }

    # start the server and block
    multi_node.listen
    multi_node.join

amqp_client.rb:

    # invoke the method over amqp and return result
    amqp_node = RJR::Nodes::AMQP.new :node_id => 'client', :broker => 'localhost'
    puts amqp_node.invoke('server-queue', 'hello', 'world')

    # send a notification via amqp,
    # notifications immediately return and always return nil
    amqp_node.notify('server-queue', 'hello', 'world')

ws_client.js:

    // use the js client to invoke the method via a websocket
    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
    <script type="text/javascript" src="site/json.js" />
    <script type="text/javascript" src="site/jrw.js" />
    <script type="text/javascript">
    var node = new Nodes::WS('127.0.0.1', '8080');
    node.onopen = function(){
      node.invoke_request('hello', 'rjr',
        function(res){
          if(res.success)
            alert(res.result);
          else
            alert(res.error);
        });
    };
    node.open();
    </script>

Reference

The source repository can be found here

Online API documentation and examples can be found here

Generate documentation via

rake yard

Also see examples and specs for detailed usage.

Advanced

Upon receiving requests from eventmachine, rjr hands them off to a thread pool to free up the reactor. It is up to the developer to ensure resources accessed in the method handlers are protected from concurrent access.

Various metadata fields are made available to json-rpc method handlers through instance variables. These include:

• @rjr_node
• @rjr_node_id
• @rjr_node_type
• @rjr_callback
• @rjr_headers
• @rjr_client_ip
• @rjr_client_port
• @rjr_method
• @rjr_method_args
• @rjr_handler

RJR implements a callback interface through which methods may be invoked on a client after an initial server connection is established. Store and/or invoke @rjr_callback to make use of this.

    node.dispatcher.handle("register_callback") do |*args|
      $my_registry.invoke_me_later {
        # rjr callback will already be setup to send messages to the correct client
        @rjr_callback.invoke 'callback_method', 'with', 'custom', 'params'
      }
    end

RJR also permits arbitrary headers being set on JSON-RPC requests and responses. These will be stored in the json send to/from nodes, at the same level/scope as the message 'id', 'method', and 'params' properties. Developers using RJR may set and leverage these headers in their registered handlers to store additional metadata to extend the JSON-RPC protocol and support any custom subsystems (an auth subsystem for example)

    node.dispatcher.handle("login") do |*args|
      if $my_user_registry.find(:user => args.first, :pass => args.last)
        @headers['session-id'] = $my_user_registry.create_session.id
      end
    done

    node.dispatcher.add_handler("do_secure_action") do |*args|
      if $my_user_registry.find(:session_id => @headers['session-id']).nil?
        raise PermissionError, "invalid session"
      end
      # ...
    end

Of course any custom headers set/used will only be of use to JSON-RPC nodes running RJR as this is not standard JSON-RPC.

Authors

• Mo Morsi mo@morsi.org
• Ladislav Smola ladislav.smola@it-logica.cz
• André Dieb Martins andre.dieb@gmail.com
• Eric Bakan eric@ebakan.com
• Jonas Collberg jonas.collberg@gmail.com