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by grey-area 1946 days ago
Sorry that should have said one binary per node really, not per service (though it is one binary per service, just on a few nodes for redundancy and load).

Services behind a load balancer so one node at a time replaced then restarted behind that, and/or you can do graceful restarts. There are a few ways.

They're run as systemd units and of course could restart for other reasons (OS Update, crash, OOM, hardware swapped out by host) - haven't noticed any problems related to that or deploys and I imagine the story is the same for other methods of running services (e.g. docker). As there is a load balancer individual nodes going down for a short time doesn't matter much.