Any success with Sinatra working together with EventMachine WebSockets?

Question

I have been using Sinatra for sometime now and I would like to add some realtime features to my web-app by pushing the data via websockets.

I have successfully used the gem 'em-websocket' on its own, but have not been able to write one ruby file that has a sinatra web server AND a web-socket server.

I've tried spinning the run! or start! methods off in separate threads with no success.

Has anyone gotten this to work?

I want to have them in the same file as I can then share variables between the two servers.

score 27 · Accepted Answer · edited Apr 17 '12 at 08:22

27

Did not try it, but should not be too hard:

require 'em-websocket'
require 'sinatra/base'
require 'thin'

EM.run do
  class App < Sinatra::Base
    # Sinatra code here
  end

  EM::WebSocket.start(:host => '0.0.0.0', :port => 3001) do
    # Websocket code here
  end

  # You could also use Rainbows! instead of Thin.
  # Any EM based Rack handler should do.
  Thin::Server.start App, '0.0.0.0', 3000
end

Also, Cramp has a websocket implementation that works directly with Thin/Rainbows! you might be able to extract, so you won't even need to run the server on another port.

edited Apr 17 '12 at 08:22

Kamiel Wanrooij

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answered Jun 09 '10 at 15:04

Konstantin Haase

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That's is pretty much how I've done it. I have a related question however which is how do I decode the `Rack::Server::Cookie` (set in the `Sinatra` class) value returned in the `handshake` passed by the client to `ws.onopen`. See my question in more detail at http://stackoverflow.com/questions/16312024/how-to-decode-a-cookie-from-the-header-of-a-websocket-connection-handshake-rub – Dave Sag May 03 '13 at 02:02

score 20 · Answer 2 · answered Jun 09 '10 at 20:22

Thanks Konstantin... that worked! I had to tweak your code slightly. I added comments where I changed it.

-poul

require 'rubygems'      # <-- Added this require
require 'em-websocket'
require 'sinatra/base'
require 'thin'

EventMachine.run do     # <-- Changed EM to EventMachine
  class App < Sinatra::Base
      get '/' do
          return "foo"
      end
  end

  EventMachine::WebSocket.start(:host => '0.0.0.0', :port => 8080) do |ws| # <-- Added |ws|
      # Websocket code here
      ws.onopen {
          ws.send "connected!!!!"
      }

      ws.onmessage { |msg|
          puts "got message #{msg}"
      }

      ws.onclose   {
          ws.send "WebSocket closed"
      }

  end

  # You could also use Rainbows! instead of Thin.
  # Any EM based Rack handler should do.
  App.run!({:port => 3000})    # <-- Changed this line from Thin.start to App.run!
end

This works well. One question though, how can the EventMachine socket events access the session info to authenticate that events are comming from a properly authenticated user? — Dave Sag, Apr 21 '13 at 08:15
I've outlined this as per my comment on @Konstanti Haase's answer, as a new question - see http://stackoverflow.com/questions/16312024/how-to-decode-a-cookie-from-the-header-of-a-websocket-connection-handshake-rub — Dave Sag, May 03 '13 at 02:03

score 17 · Answer 3 · answered Mar 30 '11 at 19:20

17

I stumbled onto this websocket-rack github project which is basically a rackified em-websocket and actually got it to work nicely side-by-side with a Sinatra app. Here's my config.ru:

require 'rubygems'
require 'rack/websocket'
require 'sinatra/base'

class WebSocketApp < Rack::WebSocket::Application
  # ...
end

class SinatraApp < Sinatra::Base
  # ...
end

map '/ws' do
  run WebSocketApp.new
end

map '/' do
  run SinatraApp
end

Have fun!
Colin

answered Mar 30 '11 at 19:20

Colin Surprenant

578
7
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2

He literally says "Here's my config.ru:". So I think "Yes" is the answer :) – Alex Martín Jiménez Nov 12 '13 at 11:40

score 12 · Answer 4 · answered Aug 14 '12 at 01:07

I've been using sinatra-websocket. It let's you run the websocket server in the same process and on the same port as Sinatra.

Disclaimer: I'm the maintainer.

require 'sinatra'
require 'sinatra-websocket'

set :server, 'thin'
set :sockets, []

get '/' do
  if !request.websocket?
    erb :index
  else
    request.websocket do |ws|
      ws.onopen do
        ws.send("Hello World!")
        settings.sockets << ws
      end
      ws.onmessage do |msg|
        EM.next_tick { settings.sockets.each{|s| s.send(msg) } }
      end
      ws.onclose do
        warn("websocket closed")
        settings.sockets.delete(ws)
      end
    end
  end
end

__END__
@@ index
<html>
  <body>
     <h1>Simple Echo & Chat Server</h1>
     <form id="form">
       <input type="text" id="input" value="send a message"></input>
     </form>
     <div id="msgs"></div>
  </body>

  <script type="text/javascript">
    window.onload = function(){
      (function(){
        var show = function(el){
          return function(msg){ el.innerHTML = msg + '<br />' + el.innerHTML; }
        }(document.getElementById('msgs'));

        var ws       = new WebSocket('ws://' + window.location.host + window.location.pathname);
        ws.onopen    = function()  { show('websocket opened'); };
        ws.onclose   = function()  { show('websocket closed'); }
        ws.onmessage = function(m) { show('websocket message: ' +  m.data); };

        var sender = function(f){
          var input     = document.getElementById('input');
          input.onclick = function(){ input.value = "" };
          f.onsubmit    = function(){
            ws.send(input.value);
            input.value = "send a message";
            return false;
          }
        }(document.getElementById('form'));
      })();
    }
  </script>
</html>

..being this the quickest way to use websocket with sinatra (to my eyes), can I ask which disadvantages this approach brings compared to using 'em-websocket', subclassing Sinatra::Base, and "manually" plugging into the event loop ? — Redoman, Dec 14 '12 at 19:38
also could anyone give a short explaination on why is "next_tick" needed here? — Redoman, Dec 16 '12 at 04:54
@@simulacre -- Any ideas how to make this work on a load balanced setup? I mean from the example above, every Sinatra process would then have its own "settings.sockets" array turning the process stateful? — Sunder, Dec 30 '12 at 03:26

score 8 · Answer 5 · edited Nov 30 '22 at 15:51

8

FYI, you can also use Padrino apps with EventMachine (as they are subsets of Sinatra apps):

require 'rubygems'
require 'eventmachine'
require 'padrino-core'
require 'thin'
require ::File.dirname(__FILE__) + '/config/boot.rb'

EM.run do
  Thin::Server.start Padrino.application, '0.0.0.0', 3000
end

edited Nov 30 '22 at 15:51

Stephen Ostermiller

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answered Dec 17 '10 at 19:54

user546469

81
1
2

Any success with Sinatra working together with EventMachine WebSockets?

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