As I understand it, there seems to no way to add a server to HAProxy without incurring significant disruption. Adding a server requires reloading configuration. This loses all statistics, all health check information, etc. So, for instance, after adding a server, HAProxy will send traffic to unhealthy servers.
I add and remove servers frequently: * HAProxy doesn't respect DNS TTLs, so I reresolve on a regular basis, and update the config. (For example, s3-1.amazon.com has 4s TTL.) * I scale the number of backend servers to match traffic patterns. Scaling actions happen at least several times a day. This is a frequently asked question about HAProxy, and reloading the configuration seems a disruptive solution ( http://serverfault.com/questions/165883/is-there-a-way-to-add-more-backend-server-to-haproxy-without-restarting-haproxy#comment181125_165885 ). I'm willing to make non-HAProxy changes in my system, e.g. with iptables, though I haven't conceived a way that anything else would solve the problem. Andreas Kohn attempted to allow adding and removing via the stats socket in 2010: http://marc.info/?t=129189972500003&r=1&w=2 What's the feasibility of adding and removing servers dynamically? Is there a better way to achieve these goals? Should I look into an HAProxy patch, or would I be wasting my time?
