README.md
# Rack Canonical Host
Rack middleware that lets you define a single host name as the canonical host
for your application. Requests for other host names will then be redirected to
the canonical host.
[](http://rubygems.org/gems/rack-canonical-host)
[](https://github.com/tylerhunt/rack-canonical-host/actions/workflows/ci.yml)
[](https://codeclimate.com/github/tylerhunt/rack-canonical-host)
## Installation
Add this line to your application’s `Gemfile`:
```ruby
gem 'rack-canonical-host'
```
And then execute:
$ bundle
Or install it yourself as:
$ gem install rack-canonical-host
## Usage
For most applications, you can insert the middleware into the `config.ru` file
in the root of the application.
Here’s a simple example of what the `config.ru` in a Rails application might
look like after adding the `Rack::CanonicalHost` middleware.
```ruby
require 'rack/canonical_host'
require ::File.expand_path('../config/environment', __FILE__)
use Rack::CanonicalHost, 'example.com'
run YourRailsApp::Application
```
In this case, any requests coming in that aren't for the specified host,
`example.com`, will be redirected, keeping the requested path intact.
### Environment-Specific Configuration
You probably don't want your redirect to happen when developing locally. One
way to prevent this from happening is to use environment variables in your
production environment to set the canonical host name.
With Heroku, you would do this like so:
$ heroku config:add CANONICAL_HOST=example.com
Then, can configure the middleware like this:
```ruby
use Rack::CanonicalHost, ENV['CANONICAL_HOST'] if ENV['CANONICAL_HOST']
```
Now, the middleware will only be used if a canonical host has been defined.
### Options
If you’d like the middleware to ignore certain hosts, use the `:ignore` option,
which accepts a string, a regular expression, a proc, or an array of those
objects.
```ruby
use Rack::CanonicalHost, 'example.com', ignore: 'api.example.com'
```
In this case, requests for the host `api.example.com` will not be redirected.
Alternatively, you can pass a block whose return value will be used as the
canonical host name.
```ruby
use Rack::CanonicalHost do |env|
case env['RACK_ENV'].to_sym
when :staging then 'staging.example.com'
when :production then 'example.com'
end
end
```
If you want it to react only on specific hosts within a multi-domain
environment, use the `:if` option, which accepts a string, a regular
expression, a `lambda` or `proc`, or an array of those objects.
```ruby
use Rack::CanonicalHost, 'example.com', if: /.*\.example\.com/
use Rack::CanonicalHost, 'example.org',
if: ->(uri) { uri.host == 'www.example.org' }
```
### Cache-Control
To avoid browsers indefinitely caching a `301` redirect, it’s a sensible idea
to set an expiry on each redirect, to hedge against the chance you may need to
change that redirect in the future.
```ruby
# Leave caching up to the browser (which could cache it indefinitely):
use Rack::CanonicalHost, 'example.com'
# Cache the redirect for up to an hour:
use Rack::CanonicalHost, 'example.com', cache_control: 'max-age=3600'
# Prevent caching of redirects:
use Rack::CanonicalHost, 'example.com', cache_control: 'no-cache'
```
## Contributing
1. Fork it
2. Create your feature branch (`git checkout -b my-new-feature`)
3. Commit your changes (`git commit -am 'Add some feature.'`)
4. Push to the branch (`git push origin my-new-feature`)
5. Create a new Pull Request
## Contributors
Thanks to the following people who have contributed patches or helpful
suggestions:
* [Pete Nicholls](https://github.com/Aupajo)
* [Tyler Ewing](https://github.com/zoso10)
* [Thomas Maurer](https://github.com/tma)
* [Jeff Carbonella](https://github.com/jcarbo)
* [Joost Schuur](https://github.com/jellybob)
* [Jon Wood](https://github.com/jellybob)
* [Peter Baker](https://github.com/finack)
* [Nathaniel Bibler](https://github.com/nbibler)
* [Eric Allam](https://github.com/ericallam)
* [Fabrizio Regini](https://github.com/freegenie)
* [Daniel Searles](https://github.com/squaresurf)
* [Sean Huber](https://github.com/shuber)
* [Olle Jonsson](https://github.com/olleolleolle)
* [Vinny Diehl](https://github.com/vinnydiehl)
* [Gareth Jones](https://github.com/G-Rath)
## Copyright
Copyright © 2009 Tyler Hunt.
Released under the terms of the MIT license. See LICENSE for details.