This evening I was fiddling around with the new proxy setup at work. We use DNS roundrobin to spread the load among our two proxy servers. I was wondering if there was any possibility to specify priorities for these 2 servers. As they are different in specifications. Then the following idea came into my mind:

- Give the 2 A records for proxy different TTLs
- e.g. proxy1 has a ttl of 600 and proxy2 a ttl of 1200
- proxy2 is the big box, proxy1 the smaller box

Why will this give priorities ? Well clients that resolve proxy and use proxy1 will refetch the proxy record after 600 seconds. And thus making use of this proxy for a minimum of 600 seconds. The same is true for proxy2 but this proxy will be used for a minimum of 1200 seconds. As the selection of A record for proxy is almost random, this will provide some sort of prioritizing.

I've configured this setup for our proxy round-robin setup and will see the results tomorrow as all customers start bashing our proxy servers. I'll keep you posted!

UPDATE 07-04-04

It seems the current TTL settings of 600 for proxy1 and 1200 for proxy2 don't have the desired effect. Loadbalancing seems almost 50/50 at the moment. I have now adjusted the TTL's to 600 for proxy1 and 3600 for proxy2. Tomorrow evening I'll have more info if this approach is effective.

UPDATE 09-04-04

Ok, using TTL's for DNS prioritizing does NOT work. Our proxies are both evenly loaded (approx 5% difference). So using TTL's for DNS priority loadbalancing will not work in practice. I'll write a new article summarizing this issue after I get back home.