How can I use a subdirectory instead of a subdomain?

You can use the rack-reverse-proxy gem that neezer found to do this. First you'll want to add gem "rack-reverse-proxy", :require => "rack/reverse_proxy" to your Gemfile and run bundle install. Next, you'll modify your config.ru to forward the /blog/ route to your desired blog:

require ::File.expand_path('../config/environment',  __FILE__)use Rack::ReverseProxy do         reverse_proxy /^\/blog(\/.*)$/, 'http://notch.tumblr.com$1', opts={:preserve_host => true}endrun YourAppName::Application

You probably already have the first require statement and the run YourAppName... statement. There are a couple important details that make this work.

First, when you add your desired blog URL, you can't keep the trailing slash on it. If you do, when someone requests http://yourdomain.com/blog/, the gem will forward them to http://you.yourbloghost.com// with an extra trailing slash.

Secondly, if the :preserve_host option isn't enabled, your blog hosting server will see the request as being for http://yourdomain.com/blog/ instead of as http://you.yourbloghost.com and will return bad results.

You still may have an issue with the CSS or images if the blog uses /absolute/paths/to/images/.

I'd say your best bet is to try and do a reverse proxy with Rack middleware (akin to Apache's mod_proxy).

A quick Google search revealed this gem ( https://github.com/jaswope/rack-reverse-proxy ), but the author mentions that it's probably not production-ready. Having a Rack middleware proxy should allow you to forward your subdomain yourdomain.com/blog to another website your-phpfog-account.com/wordpress-installation.

As far as I can tell you can't access the Apache config file with heroku if you could you could use a Rewrite rule.

If you choose not to use heroku you can always do what I detail below.. However if you're not using heroku you could just as easily extract wordpress to the /public/ rails folder and once again use a rewrite rule to get apache to handle the blog requests.

In your apache configuration you'll need to add.

RewriteRule ^/blog/?(.*)$ http://somedomain.com/~user/blog/$1 [P,NC,QSA,L]

It will redirect all requests to /blog/ to the other server.

Source: http://www.igvita.com/2007/07/04/integrating-wordpress-and-rails/