Automatically set your Ngrok tunnel as default Rails host for development environment

Ever needed to test your Rails app's emails or background jobs in a local environment but also wanted to expose it through a public URL? Here's a handy trick to dynamically set your default URL options based on Ngrok's current public URL.

Note that you should fire up ngrok before starting your local server. Also this will just grab the first tunnel you have active.

Code: config/initializers/default_url_options.rb

if Rails.env.local?
  ngrok_results = `curl -s -X GET -H "Authorization: Bearer <NGROK_API_KEY>" -H "Ngrok-Version: 2"`
  ngrok_results = JSON.parse(ngrok_results)
  public_url = ngrok_results.dig("tunnels", 0, "public_url")
  host = public_url.gsub("https://", "")
  Rails.application.routes.default_url_options = { host: host }
  Rails.application.routes.default_url_options[:host] = "<YOUR PRODUCTION HOST>"

How it Works:

  • Checks if the environment is local.
  • Fetches the current Ngrok public URL using the Ngrok API.
  • Parses the JSON response to get the public URL.
  • Updates the default_url_options for the Rails application with this public URL.

Note: Replace <NGROK_API_KEY> and <YOUR PRODUCTION HOST> with your actual keys and host.

Feel free to tweak it!