Directing dynamic subdomains to particular servers

We're building a multitenant SAAS app. Each customer gets its own subdomain, http://customername.mycompany.com. Each cust开发者_运维技巧omer will have many gigabytes of data, which means that they have to be assigned to a particular server and stay there.

If I have a server farm, and a request comes in for a particular customer, how do I direct the request to the right server?

My thought is that I'll have to create some kind of custom, programmable load balancer that will know where each customer lives and proxy the request through.

Is there an easier way?

If not, where do I find such a load balancer? The ones I've found online act more like appliances than applications which could go query a database to find the right destination server.

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I think the answer is in the question; you mention that the user will connect to username.mycompany.com. So use a DNS A record to point them to a particular IP.

In the future, if you wanted to load balance the user across (say 2) servers, you could create a virtual IP on a load balancer appliance (running LVS for example), and then point the A record to the Virtual IP created by the LB, and distribute the user across a group of servers that you have configured.

This is why using subdomains is simpler than having URL based access such as company.com/username, in which case you would have to inspect the content of the packet to see the requested URL. By using subdomains, everything can be done at the IP layer.