How to dynamically create sub-domains with different IP than the original domain correctly and efficiently?

Question

How to efficiently create subdomains dynamically that are resolved to different IP than the original domain?

Most dynamic subdomain creation solutions I've found here would add a *.domain.com A-record to the DNS server (usually using BIND), but that's not what I want.

Does that mean the zone file needs to be set to always Expire? Wouldn't that tax our DNS server heavily?

However, what if the client ISP doesn't go and fetch the new zone file I just dynamically changed? Wouldn't they not able to resolve our new sub-domain entry?

Would setting up DDNS in BIND be the logical path for implementing such system? DDNS would allow me dynamically insert A-record without restarting BIND, right?

I'm sure there are some way to do this, since most large blogging service that doesn't point all account to the same IP as the blogging engine, are doing something similar to what I need.

Thank you!

Answer 1

I would imagine that most services that do this have their wildcard (*.) DNS entry setup for these accounts, and probabley point it to a load balancer, that distributes requests based on host name etc. They then have the non-standard entrys setup as normal A records in DNS.

Answer 2

Yes, you could use dynamic DNS updates to push zone file changes into your zone without having to put them into a text zone file and reloading BIND each time.

Many large domain name registries use exactly that technique whenever a domain name is registered.

That doesn't mean, though, that it's the right technique for your application. As recommended yesterday to your other question, there's really no reason not to go with the wildcard option.

A low-end server running Apache would be more than enough to front-end reverse proxy your first few thousand sites, and better still you don't even need to deploy it until you get enough users to set up your second partitioned cluster.