c2p: add random number to xDS node ID in google-c2p resolver (#4519)

Author: menghanl

internal/grpcrand/grpcrand.go

@@ -31,26 +31,30 @@ var (
 	mu sync.Mutex
 )
 
+// Int implements rand.Int on the grpcrand global source.
+func Int() int {
+	mu.Lock()
+	defer mu.Unlock()
+	return r.Int()
+}
+
 // Int63n implements rand.Int63n on the grpcrand global source.
 func Int63n(n int64) int64 {
 	mu.Lock()
-	res := r.Int63n(n)
-	mu.Unlock()
-	return res
+	defer mu.Unlock()
+	return r.Int63n(n)
 }
 
 // Intn implements rand.Intn on the grpcrand global source.
 func Intn(n int) int {
 	mu.Lock()
-	res := r.Intn(n)
-	mu.Unlock()
-	return res
+	defer mu.Unlock()
+	return r.Intn(n)
 }
 
 // Float64 implements rand.Float64 on the grpcrand global source.
 func Float64() float64 {
 	mu.Lock()
-	res := r.Float64()
-	mu.Unlock()
-	return res
+	defer mu.Unlock()
+	return r.Float64()
 }

xds/googledirectpath/googlec2p.go

@@ -35,6 +35,7 @@ import (
 	"google.golang.org/grpc/grpclog"
 	"google.golang.org/grpc/internal/googlecloud"
 	internalgrpclog "google.golang.org/grpc/internal/grpclog"
+	"google.golang.org/grpc/internal/grpcrand"
 	"google.golang.org/grpc/internal/xds/env"
 	"google.golang.org/grpc/resolver"
 	_ "google.golang.org/grpc/xds" // To register xds resolvers and balancers.
@@ -152,13 +153,15 @@ var ipv6EnabledMetadata = &structpb.Struct{
 	},
 }
 
+var id = fmt.Sprintf("C2P-%d", grpcrand.Int())
+
 // newNode makes a copy of defaultNode, and populate it's Metadata and
 // Locality fields.
 func newNode(zone string, ipv6Capable bool) *v3corepb.Node {
 	ret := &v3corepb.Node{
 		// Not all required fields are set in defaultNote. Metadata will be set
 		// if ipv6 is enabled. Locality will be set to the value from metadata.
-		Id:                   "C2P",
+		Id:                   id,
 		UserAgentName:        gRPCUserAgentName,
 		UserAgentVersionType: &v3corepb.Node_UserAgentVersion{UserAgentVersion: grpc.Version},
 		ClientFeatures:       []string{clientFeatureNoOverprovisioning},

xds/googledirectpath/googlec2p_test.go

@@ -194,7 +194,7 @@ func TestBuildXDS(t *testing.T) {
 			}
 
 			wantNode := &v3corepb.Node{
-				Id:                   "C2P",
+				Id:                   id,
 				Metadata:             nil,
 				Locality:             &v3corepb.Locality{Zone: testZone},
 				UserAgentName:        gRPCUserAgentName,