I was thinking of locksmith. It's nice, as you say, to be able to have no more than N nodes per pool restart at any time, so that rolling updates are automatic

I was thinking of locksmith. It's nice, as you say, to be able to have no more than N nodes per pool restart at any time, so that rolling updates are automatic and in the background. You can't replicate it easily without a cluster-wide etcd and ignition. I forgot about matchbox. There was also good old fleet, but that one is dead.