steno upgrade - Githubissues

oxidecomputer / omicron

Omicron: Oxide control plane

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steno upgrade #2318

Open davepacheco opened 1 year ago

davepacheco commented 1 year ago

RFD 289 describes a few pieces required for Steno upgrade:

[ ] Nexus should only ever run sagas created by the same version of the software. In the absence of #2317, and if we never upgrade Nexus instances in-place, then maybe there's not much we need to do here? Because Nexus today should only recover sagas that it created, and a given instance will always be on one version.
[ ] Sagas need to be drained from Nexus instances during upgrade.

davepacheco commented 10 months ago

Alternatively: if we know a given Nexus is definitely not running (and especially if it will never run again), we could have an operation that assigns its sagas to another Nexus instance running the same image. This seems important for the sled removal case, where we can't actually drain old sagas. You could think of this as a simple, constrained, controlled case of failover.