How would you show “out of cluster nodes”? You’re by definition not connected to them, hence have no knowledge of them. You cannot infer anything about disconnected nodes status. They could be up, down or anywhere in between and that’s only if you know about them existing in the first place. Things get a bit better if you can (somewhat) statically define how the cluster is meant to look like and figure out which subset of the cluster has a quorum and stop doing work if no quorum can be reached.
These are quite classical distributed computing complexities. If those are new to you there’s the two generals’ problem thought experiment commonly pulled out.
