Say someone makes an HTTP get/post request to api.example.com/a/b
Now say I have ten servers setup as my backend servers.
I want a proxy to act as a load balancer, and during the request, handshake responds with:
apiX.example.com/a/b
where X is a number in the range 1..10
If HAProxy isn't the right tool for this, what would you suggest?
What benefits to hardware-based load balancers offer?
Update
Generally, from what I understand of proxies is that HAProxy will take a request, and proxy it to a backend server, wait for the response, and then send the answer to the client. The client has no idea which backend server responded to their request.
Now, if I have ten backend servers, the HAProxy server will be overloaded since it will have to handle the throughput of 10 servers traffic/bandwidth since all requests and responses are going through the HAProxy server.
I am curious if HAProxy could hand off the request to a particular backend server, and then the client will talk directly with the backend server (the backend will be publicly accessible at api3.example.com or api[1..10].example.com)
The client will be making only a single request, so the session will last for a single application only where the client makes an HTTP get/post request and waits for a response, that's it.
Best Answer
This can be possible or not depending on your setup. If your clients are configured to use a proxy server (which is HAproxy) or you are always transparently proxying all requests to HAproxy, then apparently your idea can not be implemented.
On the other hand, if the name api.example.com points to Haproxy host itself. You can use
redirectto send 302 HTTP codes to your clients. The redirects should point to one of the backend servers. Then, you need to find a way to use differentredirectstatements for different backend servers based on some criteria. You can choose something changing randomly such as source port or source IP.