The other week I had to speed up an end point of an API I’m working on, and since I wanted to do it right I used metrics. A coworker pointed me on to ActiveSupport::Notification.instrument previously so I gave it a go here.
I ended up creating a module that you can include into a class which will instrument every method. I don’t think it’s the nicest code ever but it was handy in getting a somewhat large class set up quickly.
It’s available in this gist, but I’ve also included it below.
lib/notifications.rb
module Notifications
extend ActiveSupport::Concern
module ClassMethods
def method_added(method_name)
@methods ||= []
return if @methods.include?(method_name) || method_name =~ /_old$/
@methods << method_name
class_eval %{alias #{method_name}_old #{method_name}}
define_method(method_name) do |*args|
instrument_name = "#{method_name}.#{self.class.name.underscore}"
ActiveSupport::Notifications.instrument(instrument_name) do
send("#{method_name}_old", *args)
end
end
end
end
end
You also need to set up something that will log the instruments so you can see them.
config/initializers/notifications.rb
ActiveSupport::Notifications.subscribe(/my_class$/) do |*args|
event = ActiveSupport::Notifications::Event.new(*args)
Rails.logger.warn "%7.2fms %s" % [event.duration, event.name]
end
