Redirecting http traffic to another server temporarily

Assume you have one box (dedicated server) that's on 24 7 and several other boxes that are user machines that have unused bandwidth. Assume you want to host several web pages. How can the dedicated server redirect http traffic to the user开发者_如何学编程 machines. It is desirable that the address field in the web browser still displays the right address, and not an ip. Ie. I don't want to redirect to another web page, I want to tell the web browser that it should request the same web page from a different server. I have been browsing through the 3xx codes, and I don't think they are made for anything like this.

It should work some what along these lines: 1. Dedicated server is online all the time. 2. User machine starts and tells the dedicated server that it's online. (several other user machines can do similarly) 3. Web browser looks up domain name and finds out that it points to dedicated server. 4. Web browser requests page. 5. Dedicated server tells web browser to repeat request to user machine

Is it possible to use some kind of redirect, and preferably tell the browser to keep sending further requests to user machine. The user machine can close down at almost any point of time, but it is assumed that the user machine will wait for ongoing transactions to finish, no closing the server program in the middle of a get or something.

What you want is called a Proxy server or load balancer that would sit in front of your web server.

The web browser would always talk to the load balancer, and the load balancer would forward the request to one of several back-end servers. No redirect is needed on the client side, as the client always thinks it is just talking to the load balancer.

ETA:

Looking at your various comments and re-reading the question, I think I misunderstood what you wanted to do. I was thinking that all the machines serving content would be on the same network, but now I see that you are looking for something more like a p2p web server setup.

If that's the case, using DNS and HTTP 30x redirects would probably be what you need. It would probably look something like this:

1. Your "master" server would serve as an entry point for the app, and would have a well known host name, e.g. "www.myapp.com".

2. Whenever a new "user" machine came online, it would register itself with the master server and a the master server would create or update a DNS entry for that user machine, e.g. "user123.myapp.com".

3. If a request came to the master server for a given page, e.g. "www.myapp.com/index.htm", it would do a 302 redirect to one of the user machines based on whatever DNS entry it had created for that machine - e.g. redirect them to "user123.myapp.com/index.htm".

Some problems I see with this approach:

First, Once a user gets redirected to a user machine, if the user machine went offline it would seem like the app was dead. You could avoid this by having all the links on every page specifically point to "www.myapp.com" instead of using relative links, but then every single request has to be routed through the "master server" which would be relatively inefficient.

You could potentially solve this by changing the DNS entry for a user machine when it goes offline to point back to the master server, but that wouldn't work without an extremely short TTL.

Another issue you'll have is tracking sessions. You probably wouldn't be able to use sessions very effectively with this setup without a shared session state server of some sort accessible by all the user machines. Although cookies should still work.

In networking, load balancing is a technique to distribute workload evenly across two or more computers, network links, CPUs, hard drives, or other resources, in order to get optimal resource utilization, maximize throughput, minimize response time, and avoid overload. Using multiple components with load balancing, instead of a single component, may increase reliability through redundancy. The load balancing service is usually provided by a dedicated program or hardware device (such as a multilayer switch or a DNS server).

and more interesting stuff in here

apart from load balancing you will need to set up more or less similar environment on the "users machines"

This sounds like 1 part proxy, 1 part load balancer, and about 100 parts disaster.

If I had to guess, I'd say you're trying to build some type of relatively anonymous torrent... But I may be wrong. If I'm right, HTTP is entirely the wrong protocol for something like this.

You could use dns, off the top of my head, you could setup a hostname for each machine that is going to serve users:

www in A xxx.xxx.xxx.xxx # ip address of machine 1
www in A xxx.xxx.xxx.xxx # ip address of machine 2
www in A xxx.xxx.xxx.xxx # ip address of machine 3

Then as others come online, you could add then to the dns entries:

www in A xxx.xxx.xxx.xxx # ip address of machine 4

Only problem is you'll have to lower the time to live (TTL) entry for each record down to make it smaller (I think the default is 86400 - 1 day)

If a machine does down, you'll have to remove the dns entry, though I do think this is the least intensive way of adding capacity to any website. Jeff Attwood has more info here: is round robin dns good enough?