Serve websites from multiple servers behind a single IP

Question

I have a network setup as illustrated below. A Windows Server 2012 R2 box with a public IP, with multiple CentOS 7 web servers behind it. Each CentOS box is a web server for multiple sites. The CentOS boxes are running Apache 2.4 and PHP 5.5.

The DNS entries for all the sites point to the public IP of Win Server (1.2.3.4).

My question is: How do I most efficiently serve the sites from the CentOS boxes, through to end users?

I've been looking at IIS reverse proxies. Here's my current (super-clunky) solution:

• Win Server gets a request for foo.com
• The URL is re-written to com.foo.web1 and IIS includes a $_SERVER variable to feed PHP the correct URL (foo.com).
• The Win Server hosts file says com.foo.web1 goes to the IP of Web1 (192.168.1.2)
• Web1 has a vhost for com.foo.web1 which then serves all the stuff for foo.com.

This works but it feels like a horrible hack. Ideally, I'd like to avoid rewriting URLs. I just want to say foo.com? Send that request to 192.168.1.2. thing.com? send that to 192.168.1.3. That sounds just like DNS to me, but obviously I can't just tell the user to go to some internal IP. Maybe I actually need a forward proxy? I can't just forward port 80 because of the need to split requests between multiple servers.

I feel like this problem must have been solved before, but I can't figure it out. (I'm really a developer, not a sys-admin). Help would be much appreciated!

I dumped Win Server for Linux and used HAProxy

To save anyone who finds this from reading through all the comments, I ended up dumping Windows Server and using Linux with HAProxy. HAProxy is able to forward the requests without re-writing the URLs.

I haven't yet found a good solution for Windows, but I think this might be acceptable:

Re-write all URLs by adding a port, so:

• foo.com -> foo.com:8081
• bar.com -> bar.com:8081
• thing.com -> thing.com:8082
• stuff.com -> stuff.com:8082

Then, on the Windows Server:

• Forward port 8081 to port 80 on Web1
• Forward port 8082 to port 80 and Web2

This is untested.

Answer 1

If you have Application Request Routing (ARR) installed, you should see a new item "Server Farms" in the IIS manager.

You can create a Server Farm with a single server 192.168.1.2.

After this, you can add a reverse proxy rule (rewrite rule) for foo.com and route it to the server farm that you created in the first step.

See http://masteringlync.com/2013/02/12/using-iis-application-request-routing-arr-as-a-tmg-replacement/ for more info

Answer 2

I've never directly played with IIS's ARR features, but according to its docs it seems like it might do what you need:

Balance loads more efficiently across servers to maximize resource utilization

IIS Application Request Routing offers administrators the ability to create powerful routing rules based on the URL, HTTP headers, and server variables to determine the most appropriate Web application server for each request. ARR makes request routing decisions at the application level, and can be used in conjunction with hardware load balancers or Windows Network Load Balancing as an added layer of control over HTTP requests. In addition, ARR enable hosting providers to route requests from clients to specific Web application servers in a server farm by creating an affinity between the client and server.

That said, I don't know if it will actually work, or even how well. I would think perhaps your time might be better spent setting up the box with Linux and using HAProxy or some other Linux load-balancer/reverse-proxy (Nginx, Apache with mod_proxy).

In fact, you might be able to do it on Windows using Apache with mod_proxy as well.

Either way, I know for a fact that HAProxy can do exactly what you want since that's what it's meant for.

Answer 3

You can override DNS with the Windows hosts file (c:\windows\system32\drivers\etc\hosts), and add the line:

192.168.1.2 foo.com

Now your Windows box, will contact 192.168.1.2 for foo.com, even if foo.com has another ip in DNS.

So if systems on the internet contact foo.com, they will look up foo.com using DNS and they will connect to your Windows box. Now if you have a 'redirect' (microsoft terminology, I prefer 'reverse proxy rule') to foo.com as a redirect rule, your windows box will lookup 'foo.com' using the hosts file and connect to your internal server.