alt Hacker NewsThanks for the both great tools. just i didn't understand one thing ? the request flow, imaging we have 10 servers where we choose this request goes to server 1 and the other goes to 7 for example. and since its zero down time, how it says server 5 is updating so till it gets up no request should go there.
I think there are two different cases here. Not sure which one you’re talking about.
1. External requests, e.g. from the internet via the reverse proxy (Caddy) running in the cluster.
The rollout works on the container, not the server level. Each container registers itself in Caddy so it knows which containers to forward and distribute requests to.
When doing a rollout, a new version of container is started first, registers in caddy, then the old one is removed. This is repeated for each service container. This way, at any time there are running containers that serve requests.
It doesn’t say any server that requests shouldn’t go there. It just updates upstreams in the caddy config to send requests to the containers that are up and healthy.
2. Service to service requests within the cluster. In this case, a service DNS name is resolved to a list of IP addresses (running containers). And the client decides which one to send a request to or whether to distribute requests among them.
When the service is updated, the client needs to resolve the name again to get the up-to-date list of IPs. Many http clients handle this automatically so using http://service-name as an endpoint typically just works. But zero downtime should still be handled by the client in this case.