RailsFiltersTracer

RailsFiltersTracer helps you find performance bottlenecks in filters of Rails Controllers. It works harmoniously with newrelic_rpm gem.

Imagine you are working on performance tuning of Rails application, and find that the response from an endpoint associated with UsersControllers#update_avatar is quite slow.

Your next step would probably be breaking down the execution time by an action itself and filters registered to the action.

With newrelic_rpm gem, you can trace each of them by calling add_method_tracer iteratively as below. This is bothersome (especially when the controller inherits another controller, in which case you also have to take care of inherited filters). 😢😢😢

class UsersController < ApplicationController
  include ::NewRelic::Agent::MethodTracer

  before_action :authenticate_user!, only: [:update_avatar]
  after_action :update_access_log, only: [:update_avatar]
  def update_avatar; end

  # call add_method_tracer class method again and again
  add_method_tracer :update_avatar
  add_method_tracer :authenticate_user!
  add_method_tracer :update_access_log
end

RailsFiltersTracer eliminates this hassle. Just register UsersController to FiltersTracer's configuration, and that's it. Performances of all the filters will be reported to the New Relic server. 🎉🎉🎉

FiltersTracer.configure do |config|
  config.register_controller UsersController
end

You can find it in the New Relic dashboard.

This is not the one in the example above.

⚠️ Currently, filters which are defined as blocks (not functions) would not be traced. This feature would be added in the future version.

Add this line to your application's Gemfile:

gem 'rails_filters_tracer'

And then execute:

$ bundle install

Add config/initializers/filters_tracer.rb file in your Rails applications, and configure as below:

Rails.application.config.after_initialize do
  FiltersTracer.configure do |config|
    # Specify a logger with which registration status of the controller is logged.
    # Default is `Rails.logger || Logger.new(STDOUT)`
    config.logger = YourCustomLogger.new

    # Specify a controller class which includes an action of your concern.
    # You can register multiple controllers.
    config.register_controller UsersController
    config.register_controller PostsController

    # Specify a controller whose self and subclasses should be monitored.
    # Registering duplicated controllers with the previous step is allowed.
    # [Tip] Registering ApplicationController would typically enables to monitor all the filters in Rails app.
    config.register_all_subcontrollers ApplicationController
  end
end

⚠️ Please do not forget to set up New Relic agent in your application.

This gem depends on rails (>= 6.0.3, < 7) and newrelic_rpm (>= 6.12, < 9). (This does not mean previous or later versions do not work with this gem. Compatibilities have not been investigated.)

For rails, the compatibility has to be investigated in a strict manner. This is because FilterTracer monkey patches ActionController objects internally, thus even the difference of minor version of rails may result in the crush.

For newrelic_rpm gem, it is required that add_method_tracer is included in NewRelic::Agent::MethodTracer module.

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/kudojp/rails_filters_tracer. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the RailsFiltersTracer project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.