class ActiveSupport::Subscriber

the sql method.
it will properly dispatch the event (ActiveSupport::Notifications::Event) to
After configured, whenever a “sql.active_record” notification is published,
subscriber, the line above should be called after your subscriber definition.
Since we need to know all instance methods before attaching the log
ActiveRecord::StatsSubscriber.attach_to :active_record
And it’s finally registered as:
end
end
end
Statsd.timing(“sql.#{event.payload}”, event.duration)
def sql(event)
class StatsSubscriber < ActiveSupport::Subscriber
module ActiveRecord
statistics about queries:
An example would be Active Record subscriber responsible for collecting
a registered object based on its given namespace.
ActiveSupport::Notifications. The subscriber dispatches notifications to
ActiveSupport::Subscriber is an object set to consume

def attach_to(namespace, subscriber=new, notifier=ActiveSupport::Notifications)

Attach the subscriber to a namespace. 
def attach_to(namespace, subscriber=new, notifier=ActiveSupport::Notifications)
  subscribers << subscriber
  subscriber.public_methods(false).each do |event|
    next if %w{ start finish }.include?(event.to_s)
    notifier.subscribe("#{event}.#{namespace}", subscriber)
  end
end

def event_stack 

def event_stack
  SubscriberQueueRegistry.get_queue(@queue_key)
end

def finish(name, id, payload) 

def finish(name, id, payload)
  finished  = Time.now
  event     = event_stack.pop
  event.end = finished
  event.payload.merge!(payload)
  method = name.split('.').first
  send(method, event)
end

def initialize 

def initialize
  @queue_key = [self.class.name, object_id].join "-"
  super
end

def start(name, id, payload) 

def start(name, id, payload)
  e = ActiveSupport::Notifications::Event.new(name, Time.now, nil, id, payload)
  parent = event_stack.last
  parent << e if parent
  event_stack.push e
end

def subscribers 

def subscribers
  @@subscribers ||= []
end