NewHealthChecker returns a new HealthChecker based on transport.

NewProxy returns a new proxy.

ErrCachedClosed means cached connection was closed by peer.

ErrNoForward means no forwarder defined.

ErrNoHealthy means no healthy proxies left.

Options holds various Options that can be set.

Proxy defines an upstream host.

Transport hold the persistent cache.

HealthChecker checks the upstream health.