SilentLogger for Rails 4 to keep NewRelic's requests out of the production log.

application.rb

# config/application.rb

require File.expand_path('../boot', __FILE__)
require 'rails/all'
require File.dirname(__FILE__) + '/../lib/silent_logger.rb'

# Require the gems listed in Gemfile, including any gems
# you've limited to :test, :development, or :production.
Bundler.require(:default, Rails.env)

module Bps
  class Application < Rails::Application
    # ...
    # Don't log NewRelic ping requests
    config.middleware.swap Rails::Rack::Logger, SilentLogger, silence: ['/newrelic-ping']
    # ...
  end
end

pages_controller.rb

# app/controllers/pages_controller.rb

class PagesController < ApplicationController

  def newrelic_ping
    render nothing: true
  end

end

routes.rb

# config/routes.rb

MyApp::Application.routes.draw do
  # ...
  get 'newrelic-ping' => 'pages#newrelic_ping'
  # ...
end

silent_logger.rb

# lib/silent_logger.rb

#
# SilentLogger can be used to keep requests out of log file
# It is best used for ping requests from uptime services like
# NewRelic, Uptime Robot, etc.
#
# Source: http://dennisreimann.de/blog/silencing-the-rails-log-on-a-per-action-basis/
#
# Include logger in your config/application.rb after require 'rails/all'
# require File.dirname(__FILE__) + '/../lib/silent_logger.rb'
#
# In application.rb or environments/production.rb swap Rails logger:
# config.middleware.swap Rails::Rack::Logger, SilentLogger, silenced: ['/newrelic-ping']
#
class SilentLogger < Rails::Rack::Logger

  def initialize(app, taggers = nil)
    @app = app
    @taggers = taggers

    if @taggers.keys.include? :silence
      @silenced_paths = @taggers[:silence]
      @taggers.delete(:silence)
    end

    super
  end

  def call(env)
    if env['X-SILENCE-LOGGER'] || @silenced_paths.include?(env['PATH_INFO'])
      Rails.logger.silence do
        @app.call(env)
      end
    else
      super(env)
    end
  end

end