On Mar 31, 2012, at 11:06 PM, David Birdsong wrote: > On Sat, Mar 31, 2012 at 7:55 PM, Kevin Heatwole <ke...@heatwoles.us> wrote: >> I would plan to automate this by having all servers included in the haproxy >> config but only the first server would initially be UP and all others DOWN. >> When a server handles a request, it makes sure that its next server is >> activated. When a server doesn't handle any requests for some time, it >> deactivates its next server (if any). > > You could implement this by monitoring your available slots on a > backend, once the slots decrease %N of total slots, spin up new > instances. Apply the same logic in reverse to turn off nodes.
You make a good point. I was also thinking of using dynamic WEIGHTs in haproxy by setting the last available server to have a WEIGHT of 1% and then when that server starts getting a steady stream of requests, up its WEIGHT to 100% and allocate a new last server. I think I could make your suggestion work, but I'd rather just have it all configured in the load balancer. I'd also rather see the load balancer have some mechanism to tell the last active server it should spin up a spare or to deactivate itself so it is completely in control.
