Support specific case of specific subscription removed while in wildc…

…ard mode

Signed-off-by: Valerian Roche <valerian.roche@datadoghq.com>

pkg/cache/v3/delta.go

@@ -53,6 +53,7 @@ func createDeltaResponse(ctx context.Context, req *DeltaRequest, state stream.St
 		}
 
 		// Compute resources for removal
+		// The resource version can be set to "" here to trigger a removal even if never returned before
 		for name := range state.GetResourceVersions() {
 			if _, ok := resources.resourceMap[name]; !ok {
 				toRemove = append(toRemove, name)

pkg/server/delta/v3/server.go

@@ -235,5 +235,13 @@ func (s *server) unsubscribe(resources []string, streamState *stream.StreamState
 			continue
 		}
 		delete(sv, resource)
+		if _, ok := sv[resource]; ok && streamState.IsWildcard() {
+			// xds protocol specifically states that if a resource if unsubscribed while a wildcard watch is present,
+			// the control-plane must return a response with either the resource set as removed (if no longer present in the snapshot)
+			// or with its content
+			// If the stream is in wildcard mode specifying an empty entry in the resource versions will either send the resource content
+			// or mark it as removed (done in createDeltaResponse)
+			state.GetResourceVersions()[resource] = ""
+		}
 	}
 }