Rack middleware for GAE health check without a trip to DB

ping_pong.rb

module PingPong # App Engine health check without a trip to DB
  class Middleware
    def initialize app, ping_path = '/status'
      @app = app
      @ping_path = ping_path
      Rails.backtrace_cleaner.add_silencer { |line| line =~ /#{File.basename(__FILE__)}/ }
    end

    def pong_code
      200
    end

    def pong_headers
      {'Content-Type' => 'application/json'}
    end

    def pong_body
      {
        hello_there: 'I am alive!',
        rails_env: ENV['RAILS_ENV'],
        service: ENV['GAE_SERVICE'],
        version: ENV['GAE_VERSION']
      }.to_json
    end

    def call env
      req = Rack::Request.new env

      if (req.get? || req.head?) && req.path.chomp('/') == @ping_path
        [pong_code, pong_headers, [pong_body]]
      else
        @app.call env
      end
    end
  end
end

Usage

copy this file to lib/middlewares/

add this to application.rb:

require_relative '../lib/middlewares/ping_pong'

use it:

config.middleware.insert_before ActionDispatch::Static, PingPong::Middleware