What is the replacement for ActionController::Base.relative_url_root?

Question

I am porting a 2.x rails app to rails3; we\'ll call it foo-app. Foo-app is one section of a larger rails app and lives at main_rails_app.com/foo-app. Previously we just set

Answer 1

I feel like I must be over-complicating this and/or missing something, but this issue has been frustrating me for a while now, and here are my notes.

Summary

There are two separate issues with two points each for dynamic and static routes:

1. how to get routing to correctly match an incoming URL
   • for routes
   • for static files
2. how to generate URLs that include the relative_root
   • via url helpers
   • for static assets

One way to solve all four points:

• Configure Nginx to strip the relative_root portion
  • This solves route matching; just write routes expecting URLs at / like development
  • Also static files are served as in development
• Set RAILS_RELATIVE_URL_ROOT environment variable
  • This solves generated static asset helpers
• Use the ScriptName middleware below (modify it to use the value from the environment)
  • This solves generated url helpers, e.g. users_path

Wrapping the Rails application in Rack::URLMap in config.ru (Christoph's answer)

# config.ru
map '/relative_root' do
  run Myapp::Application
end

• requires incoming URL contain the relative_url_root (Nginx can be configured to remove or retain this; see below)
• Rack appends the relative_url_root to the Rack env SCRIPT_NAME rack/urlmap.rb:62
• Rails adds the current request's SCRIPT_NAME to url_for options metal/url_for.rb:41
• Rails' url_for prepends the script name when generating paths routing/url_for.rb:133

So that covers URLs generated by the url helpers, e.g. given UserController, users_path will be prefixed by the relative url root.

Set SCRIPT_NAME in middleware

# config.ru
class ScriptName
  def initialize(app, name)
    @app = app
    @name = name
  end

  def call(env)
    env['SCRIPT_NAME'] += @name
    @app.call(env)
  end
end

use ScriptName, '/relative_root'
run Rails.application

• Has same effect as above, but
• Requires that incoming URL NOT contain the relative_url_root

Setting RAILS_RELATIVE_URL_ROOT

• value is saved in app.config.relative_url_root configuration.rb:41
• which in turn affects asset paths asset_url_helper.rb:137
• but that's it as far as I see
• notably does not affect url helpers

Setting config.action_controller.relative_url_root

• ?? May affect assets compilation?
• Overrides RAILS_RELATIVE_URL_ROOT env var?

Explicitly defining all routes under /relative_root (rizzah's answer)

# config/routes.rb
Myapp::Application.routes.draw do
  scope '/relative_root' do
    ...
  end
end

• Url helpers will generate correct urls
• Incoming URL must contain the relative url root (sensitive to Nginx configuration, see below), else "no route matches" exceptions
• URLs requesting static assets, e.g. /relative_root/images/logo.png will result in "no route matches" exceptions. This may not be an issue if nginx is serving static assets anyway.

Nginx config

Given a config like this:

upstream myapp {
  server localhost:3000;
}

server {
  ...
  location /relative_root {
    proxy_pass http://myapp/;
  }
}

Nginx will strip out the /relative_root, and the Rails app will not see it. If you need the Rails app so see it, one way is to change the proxy_pass line:

...
    proxy_pass http://myapp/relative_root/;
...