# File actionpack/lib/action_dispatch/middleware/server_timing.rb, line 9
def initialize(app)
  @app = app
end

# File actionpack/lib/action_dispatch/middleware/server_timing.rb, line 13
def call(env)
  events = []
  subscriber = ActiveSupport::Notifications.subscribe(/.*/) do |*args|
    events << ActiveSupport::Notifications::Event.new(*args)
  end

  status, headers, body = begin
    @app.call(env)
  ensure
    ActiveSupport::Notifications.unsubscribe(subscriber)
  end

  header_info = events.group_by(&:name).map do |event_name, events_collection|
    "#{event_name};dur=#{events_collection.sum(&:duration)}"
  end
  headers[SERVER_TIMING_HEADER] = header_info.join(", ")

  [ status, headers, body ]
end