AddrMetadata is address metadata, collected from a snapshot of address list by a router, if it implements Poolable.

Cache caches all addresses relevant info for a snapshot of received invokers.

Poolable caches address pool and address metadata for a router instance which will be used later in Router's Route.

PriorityRouter routes with priority.

PriorityRouterFactory creates priority router with url.

AddrPool is an address pool, backed by a snapshot of address list, divided into categories.