module ActiveSupport::Notifications

def instrument(name, payload = {})
  if notifier.listening?(name)
    instrumenter.instrument(name, payload) { yield payload if block_given? }
  else
    yield payload if block_given?
  end
end

def instrumenter
  registry[notifier] ||= Instrumenter.new(notifier)
end

two events.
duration is important. For example, computing elapsed time between
Daylights Savings). Use +monotonic_subscribe+ when accuracy of time
time. Monotonic time will not jump forward or backward (due to NTP or
+finish+ block arguments are in monotonic time instead of wall-clock
Performs the same functionality as #subscribe, but the +start+ and

def monotonic_subscribe(pattern = nil, callback = nil, &block)
  notifier.subscribe(pattern, callback, monotonic: true, &block)
end

def publish(name, *args)
  notifier.publish(name, *args)
end

:nodoc:

def publish_event(event) # :nodoc:
  notifier.publish_event(event)
end

def registry
  ActiveSupport::IsolatedExecutionState[:active_support_notifications_registry] ||= {}
end

#=> ArgumentError (pattern must be specified as a String, Regexp or empty)
ActiveSupport::Notifications.subscribe(:render) {|*args| ...}

Raises an error if invalid event name type is passed:

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

it will yield an event object to the block:
If the block passed to the method only takes one parameter,

end
payload # => Hash, the payload
id # => String, unique ID for the instrumenter that fired the event
finish # => Time, when the instrumented block ended execution
start # => Time, when the instrumented block started execution
name # => String, name of the event (such as 'render' from above)
ActiveSupport::Notifications.subscribe('render') do |name, start, finish, id, payload|

The +block+ will receive five parameters with information about the event:

end
@event = ActiveSupport::Notifications::Event.new(*args)
ActiveSupport::Notifications.subscribe(/render/) do |*args|

names, or by passing a Regexp to match all events that match a pattern.
You can subscribe to events by passing a String to match exact event

Subscribe to a given event name with the passed +block+.

def subscribe(pattern = nil, callback = nil, &block)
  notifier.subscribe(pattern, callback, monotonic: false, &block)
end

def subscribed(callback, pattern = nil, monotonic: false, &block)
  subscriber = notifier.subscribe(pattern, callback, monotonic: monotonic)
  yield
ensure
  unsubscribe(subscriber)
end

def unsubscribe(subscriber_or_name)
  notifier.unsubscribe(subscriber_or_name)
end