Notifications provides an instrumentation API for Ruby. To instrument an action in Ruby you just need to do:

  ActiveSupport::Notifications.instrument(:render, :extra => :information) do
    render :text => "Foo"
  end

You can consume those events and the information they provide by registering a log subscriber. For instance, let‘s store all instrumented events in an array:

  @events = []

  ActiveSupport::Notifications.subscribe do |*args|
    @events << ActiveSupport::Notifications::Event.new(*args)
  end

  ActiveSupport::Notifications.instrument(:render, :extra => :information) do
    render :text => "Foo"
  end

  event = @events.first
  event.name      # => :render
  event.duration  # => 10 (in milliseconds)
  event.payload   # => { :extra => :information }

When subscribing to Notifications, you can pass a pattern, to only consume events that match the pattern:

  ActiveSupport::Notifications.subscribe(/render/) do |event|
    @render_events << event
  end

Notifications ships with a queue implementation that consumes and publish events to log subscribers in a thread. You can use any queue implementation you want.