Upgraded Rails to 6, getting Blocked host Error

Question

I needed the new function in ActiveStorage to resize_to_fill so I upgraded to Ruby 2.5.1 and Rails 6.

ruby '2.5.1'

gem "rails", github: "rails/rails"

When I stopped, then restarted my server (Cloud 9), I received the below Rails error:

Blocked host: xxxxxxx-xxxxxxx.c9users.io
To allow requests to xxxxxxx-xxxxxxx.c9users.io, add the following configuration:

Rails.application.config.hosts << "xxxxxxx-xxxxxxx.c9users.io"

I've tried restarting, new windows, but nothing worked. I've never seen this error before. I'm guessing the new version of Rails is doing something?

Answer 1

The Blocked Host is a new feature of Rails 6. You can add this pattern to your config/environments/development.rb to have no worries of that in case of dynamic urls

config.hosts << /[a-z0-9]+\.c9users\.io/

Also for ngrok user, just replace above c9users by ngrok

Update: ngrok is currently using - and . as subdomain in their URLs so this should be accurate config.hosts << /[a-z0-9-.]+\.ngrok\.io/

Source: https://github.com/MikeRogers0/puma-ngrok-tunnel

Answer 2

If you want to disable this functionality on your development environment, you can add config.hosts.clear to config/environments/development.rb.

Answer 3

Add this line to config/environments/development.rb

config.hosts << /.*\.ngrok\.io/

Restart your rails server and it will work