livestats.rb

class LiveStats
  
  def initialize(app, cache, options={})
    @app = app
    @cache = cache
    @period = options[:period] || 3600
    @precision = options[:precision] || 10
  end

  def inc(key, value=1, timeout=nil)
    if @cache.incr(key, value).nil?
      @cache.add(key, value, timeout || @period)
    end
  end

  def call(env) 
    env["rack.livestats.track"] = true
    now = Time::now
    
    response = @app.call(env)
    
    if env["rack.livestats.track"]
      ts = ((Time::now - now) * 1000).to_i # in ms
      key = Time::now.to_i / @precision
      
      # time spent
      inc("t"+key.to_s, ts)
      # visits
      inc("v"+key.to_s)
    end

    response
  end
end