ruby - Missing host to link to! Please provide the :host parameter, for Rails 4

Question

Missing host to link to! Please provide the :host parameter, set default_url_options[:host], or set :only_path to true

I randomly get this error at time, generally restarting the server fixes the issue for a while, and then it shows up again. I have added config.action_mailer.default_url_options = "localhost:3000", in the development and test.rb files.

Also, I have used include Rails.application.routes.url_helpers in one module to get access to the routes, I read this could be the reason I get these errors but removing it will leave me with no access to the routes.
The module is for the datatables gem.

Answer 1

For Rails 5, use:

Rails.application.routes.default_url_options[:host] = "XXX"

You can put this in a config/environments/ file (or any other initializer), or e.g. at the beginning of config/routes.rb.