feat: support third party orm to interact with go-zero (#1286)

* fixes #987

* chore: fix test failure

* chore: add comments

* feat: support third party orm to interact with go-zero

* chore: refactor

zrpc/resolver/internal/kubebuilder.go

@@ -0,0 +1,80 @@
+package internal
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/tal-tech/go-zero/core/logx"
+	"github.com/tal-tech/go-zero/core/proc"
+	"github.com/tal-tech/go-zero/core/threading"
+	"github.com/tal-tech/go-zero/zrpc/resolver/internal/kube"
+	"google.golang.org/grpc/resolver"
+	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/client-go/informers"
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/rest"
+)
+
+const (
+	resyncInterval = 5 * time.Minute
+	nameSelector   = "metadata.name="
+)
+
+type kubeBuilder struct{}
+
+func (b *kubeBuilder) Build(target resolver.Target, cc resolver.ClientConn,
+	opts resolver.BuildOptions) (resolver.Resolver, error) {
+	svc, err := kube.ParseTarget(target)
+	if err != nil {
+		return nil, err
+	}
+
+	config, err := rest.InClusterConfig()
+	if err != nil {
+		return nil, err
+	}
+
+	cs, err := kubernetes.NewForConfig(config)
+	if err != nil {
+		return nil, err
+	}
+
+	handler := kube.NewEventHandler(func(endpoints []string) {
+		var addrs []resolver.Address
+		for _, val := range subset(endpoints, subsetSize) {
+			addrs = append(addrs, resolver.Address{
+				Addr: fmt.Sprintf("%s:%d", val, svc.Port),
+			})
+		}
+
+		if err := cc.UpdateState(resolver.State{
+			Addresses: addrs,
+		}); err != nil {
+			logx.Error(err)
+		}
+	})
+	inf := informers.NewSharedInformerFactoryWithOptions(cs, resyncInterval,
+		informers.WithNamespace(svc.Namespace),
+		informers.WithTweakListOptions(func(options *v1.ListOptions) {
+			options.FieldSelector = nameSelector + svc.Name
+		}))
+	in := inf.Core().V1().Endpoints()
+	in.Informer().AddEventHandler(handler)
+	threading.GoSafe(func() {
+		inf.Start(proc.Done())
+	})
+
+	endpoints, err := cs.CoreV1().Endpoints(svc.Namespace).Get(context.Background(), svc.Name, v1.GetOptions{})
+	if err != nil {
+		return nil, err
+	}
+
+	handler.Update(endpoints)
+
+	return &nopResolver{cc: cc}, nil
+}
+
+func (b *kubeBuilder) Scheme() string {
+	return KubernetesScheme
+}