*: Introduce the service registry

pkg/autoscaling/service.go

@@ -27,7 +27,7 @@ import (
 const autoScalingPrefix = "/autoscaling"
 
 var (
-	autoscalingServiceGroup = server.ServiceGroup{
+	autoscalingServiceGroup = server.APIServiceGroup{
 		Name:       "autoscaling",
 		Version:    "v1alpha",
 		IsCore:     false,
@@ -36,7 +36,7 @@ var (
 )
 
 // NewHandler creates a HTTP handler for auto scaling.
-func NewHandler(_ context.Context, svr *server.Server) (http.Handler, server.ServiceGroup, error) {
+func NewHandler(_ context.Context, svr *server.Server) (http.Handler, server.APIServiceGroup, error) {
 	autoScalingHandler := http.NewServeMux()
 	rd := render.New(render.Options{
 		IndentJSON: true,

pkg/dashboard/dashboard.go

@@ -34,14 +34,14 @@ import (
 )
 
 var (
-	apiServiceGroup = server.ServiceGroup{
+	apiServiceGroup = server.APIServiceGroup{
 		Name:       "dashboard-api",
 		Version:    "v1",
 		IsCore:     false,
 		PathPrefix: config.APIPathPrefix,
 	}
 
-	uiServiceGroup = server.ServiceGroup{
+	uiServiceGroup = server.APIServiceGroup{
 		Name:       "dashboard-ui",
 		Version:    "v1",
 		IsCore:     false,
@@ -68,7 +68,7 @@ func GetServiceBuilders() []server.HandlerBuilder {
 	// The order of execution must be sequential.
 	return []server.HandlerBuilder{
 		// Dashboard API Service
-		func(ctx context.Context, srv *server.Server) (http.Handler, server.ServiceGroup, error) {
+		func(ctx context.Context, srv *server.Server) (http.Handler, server.APIServiceGroup, error) {
 			distroutil.MustLoadAndReplaceStrings()
 
 			if cfg, err = adapter.GenDashboardConfig(srv); err != nil {
@@ -98,7 +98,7 @@ func GetServiceBuilders() []server.HandlerBuilder {
 			return apiserver.Handler(s), apiServiceGroup, nil
 		},
 		// Dashboard UI
-		func(context.Context, *server.Server) (http.Handler, server.ServiceGroup, error) {
+		func(context.Context, *server.Server) (http.Handler, server.APIServiceGroup, error) {
 			if err != nil {
 				return nil, uiServiceGroup, err
 			}

pkg/dashboard/without_dashboard.go

@@ -29,7 +29,7 @@ import (
 )
 
 var (
-	serviceGroup = server.ServiceGroup{
+	serviceGroup = server.APIServiceGroup{
 		Name:       "dashboard",
 		Version:    "v1",
 		IsCore:     false,
@@ -43,7 +43,7 @@ func SetCheckInterval(time.Duration) {}
 // GetServiceBuilders returns a empty Dashboard Builder
 func GetServiceBuilders() []server.HandlerBuilder {
 	return []server.HandlerBuilder{
-		func(context.Context, *server.Server) (http.Handler, server.ServiceGroup, error) {
+		func(context.Context, *server.Server) (http.Handler, server.APIServiceGroup, error) {
 			handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 				_, _ = io.WriteString(w, "Dashboard is not built.\n")
 			})

pkg/msc/docs.go

@@ -0,0 +1,16 @@
+// Copyright 2022 TiKV Project Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package mcs used to implement the core logic of the external services which rely on the PD banckend provider.
+package mcs

pkg/msc/registry/registry.go

@@ -0,0 +1,92 @@
+// Copyright 2022 TiKV Project Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package registry is used to register the services.
+// TODO: Remove the `pd/server“ dependencies
+// TODO: Use `uber/fx` to manage the lifecycle of services.
+package registry
+
+import (
+	"net/http"
+
+	"github.com/pingcap/log"
+	"github.com/tikv/pd/server"
+	"go.uber.org/zap"
+	"google.golang.org/grpc"
+)
+
+var (
+	// ServerServiceRegistry is the global grpc service registry.
+	ServerServiceRegistry = newServiceRegistry()
+)
+
+// ServiceBuilder is a function that creates a grpc service.
+type ServiceBuilder func(*server.Server) RegistrableService
+
+// RegistrableService is the interface that should wraps the RegisterService method.
+type RegistrableService interface {
+	RegisterGRPCService(g *grpc.Server)
+	RegisterRESTHandler(userDefineHandlers map[string]http.Handler)
+}
+
+// ServiceRegistry is a map that stores all registered grpc services.
+// It implements the `server.Serviceregistry` interface.
+type ServiceRegistry struct {
+	builders map[string]ServiceBuilder
+	services map[string]RegistrableService
+}
+
+func newServiceRegistry() *ServiceRegistry {
+	return &ServiceRegistry{
+		builders: make(map[string]ServiceBuilder),
+		services: make(map[string]RegistrableService),
+	}
+}
+
+// InstallAllGRPCServices installs all registered grpc services.
+func (r *ServiceRegistry) InstallAllGRPCServices(srv *server.Server, g *grpc.Server) {
+	for name, builder := range r.builders {
+		if l, ok := r.services[name]; ok {
+			l.RegisterGRPCService(g)
+			continue
+		}
+		l := builder(srv)
+		l.RegisterGRPCService(g)
+		log.Info("grpc service registered", zap.String("service-name", name))
+	}
+}
+
+// InstallAllRESTHandler installs all registered REST services.
+func (r *ServiceRegistry) InstallAllRESTHandler(srv *server.Server, h map[string]http.Handler) {
+	for name, builder := range r.builders {
+		if l, ok := r.services[name]; ok {
+			l.RegisterRESTHandler(h)
+			continue
+		}
+		l := builder(srv)
+		l.RegisterRESTHandler(h)
+		log.Info("restful API service registered", zap.String("service-name", name))
+	}
+}
+
+// RegisterService registers a grpc service.
+func (r ServiceRegistry) RegisterService(name string, service ServiceBuilder) {
+	r.builders[name] = service
+}
+
+func init() {
+	server.NewServiceregistry = func() server.Serviceregistry {
+		return ServerServiceRegistry
+	}
+}

pkg/swaggerserver/swaggerserver.go

@@ -24,7 +24,7 @@ import (
 const swaggerPrefix = "/swagger/"
 
 var (
-	swaggerServiceGroup = server.ServiceGroup{
+	swaggerServiceGroup = server.APIServiceGroup{
 		Name:       "swagger",
 		Version:    "v1",
 		IsCore:     false,
@@ -33,7 +33,7 @@ var (
 )
 
 // NewHandler creates a HTTP handler for Swagger.
-func NewHandler(context.Context, *server.Server) (http.Handler, server.ServiceGroup, error) {
+func NewHandler(context.Context, *server.Server) (http.Handler, server.APIServiceGroup, error) {
 	swaggerHandler := http.NewServeMux()
 	swaggerHandler.Handle(swaggerPrefix, handler())
 	return swaggerHandler, swaggerServiceGroup, nil

pkg/utils/apiutil/serverapi/middleware.go

@@ -40,11 +40,11 @@ const (
 
 type runtimeServiceValidator struct {
 	s     *server.Server
-	group server.ServiceGroup
+	group server.APIServiceGroup
 }
 
 // NewRuntimeServiceValidator checks if the path is invalid.
-func NewRuntimeServiceValidator(s *server.Server, group server.ServiceGroup) negroni.Handler {
+func NewRuntimeServiceValidator(s *server.Server, group server.APIServiceGroup) negroni.Handler {
 	return &runtimeServiceValidator{s: s, group: group}
 }
 
@@ -58,7 +58,7 @@ func (h *runtimeServiceValidator) ServeHTTP(w http.ResponseWriter, r *http.Reque
 }
 
 // IsServiceAllowed checks the service through the path.
-func IsServiceAllowed(s *server.Server, group server.ServiceGroup) bool {
+func IsServiceAllowed(s *server.Server, group server.APIServiceGroup) bool {
 	// for core path
 	if group.IsCore {
 		return true

server/api/server.go

@@ -27,8 +27,8 @@ import (
 const apiPrefix = "/pd"
 
 // NewHandler creates a HTTP handler for API.
-func NewHandler(ctx context.Context, svr *server.Server) (http.Handler, server.ServiceGroup, error) {
-	group := server.ServiceGroup{
+func NewHandler(ctx context.Context, svr *server.Server) (http.Handler, server.APIServiceGroup, error) {
+	group := server.APIServiceGroup{
 		Name:   "core",
 		IsCore: true,
 	}

server/apiv2/router.go

@@ -27,7 +27,7 @@ import (
 
 var once sync.Once
 
-var group = server.ServiceGroup{
+var group = server.APIServiceGroup{
 	Name:       "core",
 	IsCore:     true,
 	Version:    "v2",
@@ -37,7 +37,7 @@ var group = server.ServiceGroup{
 const apiV2Prefix = "/pd/api/v2/"
 
 // NewV2Handler creates a HTTP handler for API.
-func NewV2Handler(_ context.Context, svr *server.Server) (http.Handler, server.ServiceGroup, error) {
+func NewV2Handler(_ context.Context, svr *server.Server) (http.Handler, server.APIServiceGroup, error) {
 	once.Do(func() {
 		// See https://github.com/pingcap/tidb-dashboard/blob/f8ecb64e3d63f4ed91c3dca7a04362418ade01d8/pkg/apiserver/apiserver.go#L84
 		// These global modification will be effective only for the first invoke.

server/server.go

@@ -67,7 +67,6 @@ import (
 	"github.com/tikv/pd/server/schedule/placement"
 	"github.com/tikv/pd/server/storage"
 	"github.com/tikv/pd/server/tso"
-	"github.com/urfave/negroni"
 	"go.etcd.io/etcd/clientv3"
 	"go.etcd.io/etcd/embed"
 	"go.etcd.io/etcd/pkg/types"
@@ -173,15 +172,7 @@ type Server struct {
 }
 
 // HandlerBuilder builds a server HTTP handler.
-type HandlerBuilder func(context.Context, *Server) (http.Handler, ServiceGroup, error)
-
-// ServiceGroup used to register the service.
-type ServiceGroup struct {
-	Name       string
-	Version    string
-	IsCore     bool
-	PathPrefix string
-}
+type HandlerBuilder func(context.Context, *Server) (http.Handler, APIServiceGroup, error)
 
 const (
 	// CorePath the core group, is at REST path `/pd/api/v1`.
@@ -190,60 +181,8 @@ const (
 	ExtensionsPath = "/pd/apis"
 )
 
-func combineBuilderServerHTTPService(ctx context.Context, svr *Server, serviceBuilders ...HandlerBuilder) (map[string]http.Handler, error) {
-	userHandlers := make(map[string]http.Handler)
-	registerMap := make(map[string]struct{})
-
-	apiService := negroni.New()
-	recovery := negroni.NewRecovery()
-	apiService.Use(recovery)
-	router := mux.NewRouter()
-
-	for _, build := range serviceBuilders {
-		handler, info, err := build(ctx, svr)
-		if err != nil {
-			return nil, err
-		}
-		if !info.IsCore && len(info.PathPrefix) == 0 && (len(info.Name) == 0 || len(info.Version) == 0) {
-			return nil, errs.ErrAPIInformationInvalid.FastGenByArgs(info.Name, info.Version)
-		}
-		var pathPrefix string
-		if len(info.PathPrefix) != 0 {
-			pathPrefix = info.PathPrefix
-		} else if info.IsCore {
-			pathPrefix = CorePath
-		} else {
-			pathPrefix = path.Join(ExtensionsPath, info.Name, info.Version)
-		}
-		if _, ok := registerMap[pathPrefix]; ok {
-			return nil, errs.ErrServiceRegistered.FastGenByArgs(pathPrefix)
-		}
-
-		log.Info("register REST path", zap.String("path", pathPrefix))
-		registerMap[pathPrefix] = struct{}{}
-		if len(info.PathPrefix) != 0 {
-			// If PathPrefix is specified, register directly into userHandlers
-			userHandlers[pathPrefix] = handler
-		} else {
-			// If PathPrefix is not specified, register into apiService,
-			// and finally apiService is registered in userHandlers.
-			router.PathPrefix(pathPrefix).Handler(handler)
-			if info.IsCore {
-				// Deprecated
-				router.Path("/pd/health").Handler(handler)
-				// Deprecated
-				router.Path("/pd/ping").Handler(handler)
-			}
-		}
-	}
-	apiService.UseHandler(router)
-	userHandlers[pdAPIPrefix] = apiService
-
-	return userHandlers, nil
-}
-
 // CreateServer creates the UNINITIALIZED pd server with given configuration.
-func CreateServer(ctx context.Context, cfg *config.Config, serviceBuilders ...HandlerBuilder) (*Server, error) {
+func CreateServer(ctx context.Context, cfg *config.Config, legacyServiceBuilders ...HandlerBuilder) (*Server, error) {
 	log.Info("PD Config", zap.Reflect("config", cfg))
 	rand.Seed(time.Now().UnixNano())
 	serviceMiddlewareCfg := config.NewServiceMiddlewareConfig()
@@ -276,18 +215,26 @@ func CreateServer(ctx context.Context, cfg *config.Config, serviceBuilders ...Ha
 	if err != nil {
 		return nil, err
 	}
-	if len(serviceBuilders) != 0 {
-		userHandlers, err := combineBuilderServerHTTPService(ctx, s, serviceBuilders...)
+	if len(legacyServiceBuilders) != 0 {
+		userHandlers, err := combineBuilderServerHTTPService(ctx, s, legacyServiceBuilders...)
 		if err != nil {
 			return nil, err
 		}
 		etcdCfg.UserHandlers = userHandlers
 	}
+	// New way to register services.
+	registry := NewServiceregistry()
+
+	// Register the micro services REST path.
+	registry.InstallAllRESTHandler(s, etcdCfg.UserHandlers)
+
 	etcdCfg.ServiceRegister = func(gs *grpc.Server) {
 		grpcServer := &GrpcServer{Server: s}
 		pdpb.RegisterPDServer(gs, grpcServer)
 		keyspacepb.RegisterKeyspaceServer(gs, &KeyspaceServer{GrpcServer: grpcServer})
 		diagnosticspb.RegisterDiagnosticsServer(gs, s)
+		// Register the micro services GRPC service.
+		NewServiceregistry().InstallAllGRPCServices(s, gs)
 	}
 	s.etcdCfg = etcdCfg
 	s.lg = cfg.GetZapLogger()