[toast0]

If you want no downtime server updates, you have choices:

a) remove server(s) from load balancing, finish requests/connections in progress, restart with new software, add to load balancing

b) hot loading

c) start a new server instance and pass it the listen socket (or if your OS isn't great, drop syns for a bit while you close the listen socket on the old server and open a new listen socket for the new server)

I like hotloading, but it's not appropriate for all updates, so you need to have a way to handle restart based updates as well.