fix: etcd scheme on grpc resolver (#4121)

zrpc/resolver/internal/discovbuilder.go

@@ -9,10 +9,41 @@ import (
 	"google.golang.org/grpc/resolver"
 )
 
-type discovBuilder struct{}
+type discovBuilder struct {
+	cc     resolver.ClientConn
+	update func()
+}
 
 func (b *discovBuilder) Build(target resolver.Target, cc resolver.ClientConn, _ resolver.BuildOptions) (
 	resolver.Resolver, error) {
+	b.cc = cc
+	if err := b.updateState(target); err != nil {
+		return nil, err
+	}
+
+	return &nopResolver{cc: cc}, nil
+}
+
+func (b *discovBuilder) Scheme() string {
+	return DiscovScheme
+}
+
+func (b *discovBuilder) updateState(target resolver.Target) error {
+	if b.update == nil {
+		update, err := b.buildEndpointsUpdater(target)
+		if err != nil {
+			return err
+		}
+
+		b.update = update
+	}
+
+	b.update()
+
+	return nil
+}
+
+func (b *discovBuilder) buildEndpointsUpdater(target resolver.Target) (func(), error) {
 	hosts := strings.FieldsFunc(targets.GetAuthority(target), func(r rune) bool {
 		return r == EndpointSepChar
 	})
@@ -29,18 +60,13 @@ func (b *discovBuilder) Build(target resolver.Target, cc resolver.ClientConn, _
 				Addr: val,
 			})
 		}
-		if err := cc.UpdateState(resolver.State{
+		if err := b.cc.UpdateState(resolver.State{
 			Addresses: addrs,
 		}); err != nil {
 			logx.Error(err)
 		}
 	}
 	sub.AddListener(update)
-	update()
 
-	return &nopResolver{cc: cc}, nil
+	return update, nil
-}
-
-func (b *discovBuilder) Scheme() string {
-	return DiscovScheme
 }

zrpc/resolver/internal/kubebuilder.go

@@ -28,7 +28,8 @@ type kubeResolver struct {
 	stopCh chan struct{}
 }
 
-func (r *kubeResolver) ResolveNow(_ resolver.ResolveNowOptions) {}
+func (r *kubeResolver) ResolveNow(_ resolver.ResolveNowOptions) {
+}
 
 func (r *kubeResolver) start() {
 	threading.GoSafe(func() {