in #17645 there was a bunch of discussion around the DNS cache returning null addresses and how to handle it. After discussion on #19461 we agreed to keep sending null updates, but to fast-fail if no address was resolved.
Risk Level: Medium (data plane change)
Testing: updated integration tests, unit tests
Docs Changes: n/a
Release Notes: inline
Signed-off-by: Alyssa Wilk <alyssar@chromium.org>
Mirrored from https://github.com/envoyproxy/envoy @ 2efe480d6b0a1501674780cfd7c343ef332010a1