Comment 1 for bug 1909031

config_changed explicitly calls rabbit.set_all_mirroring_queues. This function always sets the policy and does not check if it was needed. There have been some upstream bugs we have hit that suggest to try and not call this function during turbulent times as it can cause some de-sync but I don't have a reference to that bug atm. But in general avoiding these types of operations when not needed is ideal.

config_changed then also calls cluster_changed "in case min-cluster-size has changed" and update_clients ("ensure all clients connections are up to date on upgrade)

cluster_changed then calls cluster_with though I couldn't see an obvious path for cluster_with to re-run the other code but it does reset relations which will fire relation changed hooks.