Rails4.0.0.beta1 + ActionController::Live + JavaScript EventSource ref: http://qiita.com/items/9369360774edfcc3c13c

file0.txt

require 'reloader/sse'

class ProgressController < ApplicationController
  include ActionController::Live

  def index
    # SSE expects the `text/event-stream` content type
    response.headers['Content-Type'] = 'text/event-stream'

    sse = Reloader::SSE.new(response.stream)

    begin
      total = 0

      (0..100).step(10).each{ |i|
        puts "[ #{i} ]"
        sse.write( "#{Time.now.strftime("%Y/%m/%d %H:%M:%S")}" + " - #{i}" )
        total += i
        sleep( rand(1..3) )
      }

      puts "[ total : #{total} ]"

      sse.write( "#{Time.now.strftime("%Y/%m/%d %H:%M:%S")}" + " - #{total}", event: 'refresh' )

      # 接続終了送信
#      sse.write("stream_end")
    rescue IOError
      # When the client disconnects, we'll get an IOError on write
    ensure
      sse.close
    end
  end

  def show
  end
end

file1.txt

require 'json'

module Reloader
  class SSE
    def initialize io
      @io = io
    end

    def write object, options = {}
      options.each do |k,v|
        @io.write "#{k}: #{v}\n"
      end
#      @io.write "data: #{JSON.dump(object)}\n\n"
      @io.write "data: #{object}\n\n"
    end

    def close
      @io.close
    end
  end
end

file10.txt

heroku create rails4sample

file11.txt

git push heroku master

file2.html

<h1>progress#show</h1>

<h3>Total</h3>

<div id="refresh"></div>

<hr />

<h3>Progress</h3>

<div id="progress"></div>

<script type="text/javascript">
  jQuery(document).ready(function() {
    setTimeout(function() {
      // 接続開始
      var source = new EventSource('/progress/index');

      // サーバー側イベントの共通ハンドラを定義
      function eventLogger(event){
        $("#progress").prepend(event.data + "<br>");

        // 接続終了判定
        if (event.data == 'stream_end') { source.close() };
      }

      // messageイベントのハンドラを設定
      source.onmessage = eventLogger;
    }, 10);
  });
</script>

<script type="text/javascript">
  jQuery(document).ready(function() {
    setTimeout(function() {
      var source = new EventSource('/progress/index');
      source.addEventListener('refresh', function(e) {
        $("#refresh").prepend(event.data + "<br>");
        // window.location.reload();

        // 接続終了判定
        if (event.data == 'stream_end') { source.close() };
      });
    }, 20);
  });
</script>

file3.txt

  get 'progress/index'
  get 'progress/show'

file4.txt

gem "puma"

file5.txt

bundle install

file6.txt

rails s puma

file7.txt

  # Disable Rails's static asset server (Apache or nginx will already do this).
#  config.serve_static_assets = false

file8.txt

web: bundle exec rails s puma -p $PORT -e $RACK_ENV

file9.txt

git init && git add . && git commit -m "First commit"