A pluggable component that resolves a target URI and return addresses to the caller.

A NameResolver uses the URI's scheme to determine whether it can resolve it, and uses the components after the scheme for actual resolution.

The addresses and attributes of a target may be changed over time, thus the caller registers a Listener to receive continuous updates.

A NameResolver does not need to automatically re-resolve on failure. Instead, the Listener is responsible for eventually (after an appropriate backoff period) invoking refresh().

Implementations don't need to be thread-safe. All methods are guaranteed to be called sequentially. Additionally, all methods that have side-effects, i.e., start(Listener2), shutdown and refresh are called from the same SynchronizationContext as returned by Args#getSynchronizationContext. Do not block within the synchronization context; blocking I/O and time-consuming tasks should be offloaded to a separate thread, generally Args#getOffloadExecutor.