Fix panic in case the resourceType is not know by the caches (#1036)

* Fix panic in case the resourceType is not know by the caches

Signed-off-by: Alan Diego dos Santos <alandiegosantos@gmail.com>
Signed-off-by: Alan Diego <alandiegosantos@gmail.com>
Co-authored-by: Alan Diego <alan.diego@booking.com>

pkg/server/sotw/v3/xds.go

@@ -149,11 +149,13 @@ func (s *server) process(str stream.Stream, reqCh chan *discovery.DiscoveryReque
 			sw.watches.recompute(s.ctx, reqCh)
 		default:
 			// Channel n -> these are the dynamic list of responders that correspond to the stream request typeURL
-			if !ok {
+			// nil is used to close the streams in the caches
+			if value.IsNil() || !ok {
 				// Receiver channel was closed. TODO(jpeach): probably cancel the watch or something?
 				return status.Errorf(codes.Unavailable, "resource watch %d -> failed", index)
 			}
 
+			// If a non cache.Response arrived here, there are serious issues
 			res := value.Interface().(cache.Response)
 			nonce, err := sw.send(res)
 			if err != nil {

pkg/server/v3/server_test.go

@@ -19,6 +19,7 @@ import (
 	"errors"
 	"fmt"
 	"reflect"
+	"strings"
 	"sync"
 	"testing"
 	"time"
@@ -52,6 +53,11 @@ type mockConfigWatcher struct {
 
 func (config *mockConfigWatcher) CreateWatch(req *discovery.DiscoveryRequest, _ stream.StreamState, out chan cache.Response) func() {
 	config.counts[req.GetTypeUrl()] = config.counts[req.GetTypeUrl()] + 1
+
+	if strings.Contains(req.GetTypeUrl(), nilType) {
+		out <- nil
+	}
+
 	if len(config.responses[req.GetTypeUrl()]) > 0 {
 		out <- config.responses[req.GetTypeUrl()][0]
 		config.responses[req.GetTypeUrl()] = config.responses[req.GetTypeUrl()][1:]
@@ -163,6 +169,7 @@ var (
 	extensionConfig    = resource.MakeExtensionConfig(resource.Ads, extensionConfigName, routeName)
 	opaque             = &core.Address{}
 	opaqueType         = "unknown-type"
+	nilType            = "nil-stream-type" // This type will force the close of the connection
 	testTypes          = []string{
 		rsrc.EndpointType,
 		rsrc.ClusterType,
@@ -659,6 +666,24 @@ func TestOpaqueRequestsChannelMuxing(t *testing.T) {
 	assert.Equal(t, 0, config.watches)
 }
 
+func TestNilPropagationOverResponseChannelShouldCloseTheStream(t *testing.T) {
+	config := makeMockConfigWatcher()
+	resp := makeMockStream(t)
+	for i := 0; i < 10; i++ {
+		resp.recv <- &discovery.DiscoveryRequest{
+			Node:    node,
+			TypeUrl: nilType,
+			// each subsequent request is assumed to supercede the previous request
+			ResourceNames: []string{fmt.Sprintf("%d", i)},
+		}
+	}
+	close(resp.recv)
+	s := server.NewServer(context.Background(), config, server.CallbackFuncs{})
+	err := s.StreamAggregatedResources(resp)
+	require.Error(t, err)
+	assert.Equal(t, 0, config.watches)
+}
+
 func TestCallbackError(t *testing.T) {
 	for _, typ := range testTypes {
 		t.Run(typ, func(t *testing.T) {