This is an xDS server that Envoy can use to discover precisely nothing.
It never delivers any config. It's only purpose is to attempt a really simple reproduction of an issue seen in integration tests against a real xDS server (Consul) which seemed to indicate a bug in Envoy. This server helps prove that's not the case.
Run the xDS server:
$ go run main.go
2019/05/03 12:15:54 Listening on :9876In another terminal run Envoy with the bootstrap here (based on the case that was failing):
$ envoy -c bootstrap.json -l debug