Sinatra Server Side Event streaming.

juggernaut.rb

# Usage: redis-cli publish message hello

require 'sinatra'
require 'redis'

conns = []

get '/' do
  erb :index
end

get '/subscribe' do
  content_type 'text/event-stream'
  stream(:keep_open) do |out| # EventMachine?
    conns << out
    out.callback { conns.delete(out) }
  end
end

Thread.new do
  redis = Redis.connect#, db: 0
  redis.psubscribe('message', 'message.*') do |on|
    on.pmessage do |match, channel, message|
      channel = channel.sub 'example message.', ''

      conns.each do |out|
        out << "event: #{channel}\n"
        out << "data:  #{message}\n"
      end
    end
  end
end

__END__
# view

@@ index
  # TODO: load opal
  <article id="log"></article>

  # client code is written and served by the server
  <script>
    var source = new EventSource('/subscribe')

    source.addEventListener('message', function (event) {
      log.innerText += '\n' + event.data
    }, false);
  </script>