//TODO: better blog title

Updated Feburary 7th, 2012

1. Create a security group on EC2 that opens ports 22 (SSH) and 80 (HTTP).
2. Start an instance on EC2 using an Ubuntu AMI. Select the security group you just created when launching the instance. I used a micro instance running the “ami-ad7e2ee8″ (32-bit Ubuntu 10.10) image. The best place to find the AMI that you want is http://cloud-images.ubuntu.com/releases/. Everything there is nicely organized by version, release type, CPU architecture, and backing storage. (As opposed to the mess of text in the EC2 classic wizard).
3. Assign an elastic ip to the instance.
4. Go to your domain registrar, and edit your DNS zonefile. Add a CNAME that points www to your “Public DNS” on EC2 (ec2-elasticip.zone.compute.amazonaws.com.). It’s important to use a CNAME record rather than an A record, because your instance will not be accessible to other EC2 instances by public IP address.
5. SSH into your server and install nginx.

If you want the latest version of nginx, you need to add these repositories to apt-get to download from nginx.org. If not, skip this block, and you will get the latest version available from Ubuntu.

cd ~
sudo echo "deb http://nginx.org/packages/ubuntu/ quantal nginx" >> /etc/apt/sources.list
sudo echo "deb-src http://nginx.org/packages/ubuntu/ quantal nginx" >> /etc/apt/sources.list
sudo wget http://nginx.org/keys/nginx_signing.key
sudo apt-key add nginx_signing.key

Now, download and install nginx.

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install nginx
sudo vi /etc/nginx/nginx.conf

6. Now, remove any existing server blocks, and add your own to /etc/nginx/nginx.conf.

server {
        listen 80;

        location / {

        }
}

server {
        listen  80;

        server_name  www.mysite.com;

        location / {
                proxy_pass  http://mysite.appspot.com;
                proxy_set_header  X-Real-IP    $remote_addr;
                proxy_set_header  X-Real-HOST  $host;
        }
}

The first server block is the default, so this blocks requests that are not for the domain you’re trying to proxy.
7. Run nginx:

sudo service nginx start

8. You should be able to access your App Engine site using your own domain. However, in your app engine request handlers, self.request.host will be set to your appspot domain, and self.request.remote_addr will be set to your ec2 ip address. We can fix this by adding some middle ware to app engine, assuming you’re using webapp or webapp2.

class ReverseProxyMiddleware(object):

	def __init__(self, application, debug=False):
		self.application = application

	def __call__(self, environ, start_response):
		real_host = environ.get('HTTP_X_REAL_HOST')
		if real_host:
			environ['HTTP_HOST'] = real_host
			environ['SERVER_NAME'] = real_host
		real_ip = environ.get('HTTP_X_REAL_IP')
		if real_ip:
			environ['REMOTE_ADDR'] = real_ip
		return self.application(environ, start_response)

To use it, wrap your WSGIApplication right after initialization.

application = WSGIApplication([
...
])
application = ReverseProxyMiddleware(application)

9. That’s it! One thing to note is that app engine cron jobs and task queues don’t know anything about your reverse proxy, so in those handlers, self.request.host will still be your appspot domain.