How do I make Envoy fail over to another region during service degradation?

Envoy uses the concept of priorities <arch_overview_load_balancing_priority_levels> to express the idea that a certain set of endpoints should be preferred over others.

By putting the preferred endpoints into the lower priority, Envoy will always select one of these endpoints as long as that priority is sufficiently available. This means that common failover scenarios can be expressed by putting the fallback endpoints in a different priority. See the priority <arch_overview_load_balancing_priority_levels> for more information about this.