Add defensive guard to make some tests less flaky and panic less

agent/xds/delta.go

@@ -47,6 +47,13 @@ type ADSDeltaStream = envoy_discovery_v3.AggregatedDiscoveryService_DeltaAggrega
 
 // DeltaAggregatedResources implements envoy_discovery_v3.AggregatedDiscoveryServiceServer
 func (s *Server) DeltaAggregatedResources(stream ADSDeltaStream) error {
+	// this guard is mainly for our tests where we sometimes nil out the
+	// server stream, any use of the stream after we nil it causes
+	// pretty much all of the below code to panic.
+	if stream == nil {
+		return nil
+	}
+
 	defer s.activeStreams.Increment(stream.Context())()
 
 	// a channel for receiving incoming requests

agent/xds/testing.go

@@ -227,6 +227,10 @@ func (e *TestEnvoy) Close() error {
 	// unblock the recv chans to simulate recv errors when client disconnects
 	if e.deltaStream != nil && e.deltaStream.recvCh != nil {
 		close(e.deltaStream.recvCh)
+		// TODO: This is causing a bunch of panics in testing code due to inflight
+		// requests attempting to grab a context from a stream that's nil. Added
+		// some defensive code in the xDS handler, but really, this should get fixed
+		// so we no longer have a data-race
 		e.deltaStream = nil
 	}
 	if e.cancel != nil {