New returns a new host index that uses the provided route activation function to determine which routes for a given host should be active.

OldestFirst identifies all unique host+port combinations in active and inactive, ordered by oldest first.

SameNamespace identifies all unique host+port combinations in active and inactive that are from the same namespace as the oldest route (creation timestamp and then uid ordering).

Changed allows a route activation function to record which routes moved from inactive to active or vice versa.

Changes lists all routes either activated or displaced by the operation.

Interface allows access to routes in the index and makes it easy to know when changes to routes alter the index.

RouteActivationFunc attempts to add routes from inactive into the active set.