一、简介
关于服务注册和服务发现介绍,我前面的文章有介绍过 - 服务注册和发现的文章。
作为服务中心的软件有很多,比如 etcd,consul,nacos,zookeeper 等都可以作为服务中心。
go-kratos 把这些服务中心的功能作为插件,集成进了 kratos 中。
下面就用 etcd 作为服务中心来说说 kratos 里服务注册和服务发现功能的使用。
二、服务注册和服务发现
2.1 接口定义
从 go-kratos 服务注册和发现文档中,我们知道它的接口定义非常简单:
注册和反注册服务:
type Registrar interface { // 注册实例 Register(ctx context.Context, service *ServiceInstance) error // 反注册实例 Deregister(ctx context.Context, service *ServiceInstance) error }
获取服务:
type Discovery interface { // 根据 serviceName 直接拉取实例列表 GetService(ctx context.Context, serviceName string) ([]*ServiceInstance, error) // 根据 serviceName 阻塞式订阅一个服务的实例列表信息 Watch(ctx context.Context, serviceName string) (Watcher, error) }
2.2 简单使用
服务端注册服务
使用 etcd 作为服务中心。
1.新建 etcd连接client, etcdregitry.New(client)
2.把 regitry传入 kratos.Registrar(r)
3.传入服务名称 kratos.Name("helloworld")
看官方的示例代码,server/main.go:
package main import ( "context" "fmt" "log" etcdregitry "github.com/go-kratos/kratos/contrib/registry/etcd/v2" "github.com/go-kratos/kratos/v2" "github.com/go-kratos/kratos/v2/middleware/recovery" "github.com/go-kratos/kratos/v2/transport/grpc" "github.com/go-kratos/kratos/v2/transport/http" pb "github.com/go-kratos/examples/helloworld/helloworld" etcdclient "go.etcd.io/etcd/client/v3" ) type server struct { pb.UnimplementedGreeterServer } func (s *server) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) { return &pb.HelloReply{Message: fmt.Sprintf("welcome %+v!", in.Name)}, nil } func main() { // 创建 etcd client 连接 client, err := etcdclient.New(etcdclient.Config{ Endpoints: []string{"127.0.0.1:2379"}, }) if err != nil { log.Fatal(err) } // 初始化 http server httpSrv := http.NewServer( http.Address(":8080"), http.Middleware( recovery.Recovery(), ), ) // 初始化 grpc server grpcSrv := grpc.NewServer( grpc.Address(":9000"), grpc.Middleware( recovery.Recovery(), ), ) // 在服务器上注册服务 s := &server{} pb.RegisterGreeterServer(grpcSrv, s) pb.RegisterGreeterHTTPServer(httpSrv, s) // 创建一个 registry 对象,就是对 ectd client 操作的一个包装 r := etcdregitry.New(client) app := kratos.New( kratos.Name("helloworld"), // 服务名称 kratos.Server( httpSrv, grpcSrv, ), kratos.Registrar(r), // 填入etcd连接(etcd作为服务中心) ) if err := app.Run(); err != nil { log.Fatal(err) } }
etcd作为服务中心的使用步骤图解:
客户端获取服务
客户端的服务发现,主要也是 3 个步骤.
1.新建 etcd连接, 传入到 etcdregitry.New(client)
2.将 registry 传入 WithDiscovery(r)
3.获取服务WithEndpoint("discovery:///helloworld")
步骤与服务没有多大区别。
官方的示例代码,client/main.go:
package main import ( "context" "log" "time" "github.com/go-kratos/examples/helloworld/helloworld" etcdregitry "github.com/go-kratos/kratos/contrib/registry/etcd/v2" "github.com/go-kratos/kratos/v2/transport/grpc" "github.com/go-kratos/kratos/v2/transport/http" etcdclient "go.etcd.io/etcd/client/v3" srcgrpc "google.golang.org/grpc" ) func main() { client, err := etcdclient.New(etcdclient.Config{ Endpoints: []string{"127.0.0.1:2379"}, }) if err != nil { log.Fatal(err) } r := etcdregitry.New(client) // 传入 etcd client,也就是选择 etcd 为服务中心 connGRPC, err := grpc.DialInsecure( context.Background(), grpc.WithEndpoint("discovery:///helloworld"), // 服务发现 grpc.WithDiscovery(r), // 传入etcd registry ) if err != nil { log.Fatal(err) } defer connGRPC.Close() connHTTP, err := http.NewClient( context.Background(), http.WithEndpoint("discovery:///helloworld"), http.WithDiscovery(r), http.WithBlock(), ) if err != nil { log.Fatal(err) } defer connHTTP.Close() for { callHTTP(connHTTP) callGRPC(connGRPC) time.Sleep(time.Second) } } func callHTTP(conn *http.Client) { client := helloworld.NewGreeterHTTPClient(conn) reply, err := client.SayHello(context.Background(), &helloworld.HelloRequest{Name: "go-kratos"}) if err != nil { log.Fatal(err) } log.Printf("[http] SayHello %+vn", reply) } func callGRPC(conn *srcgrpc.ClientConn) { client := helloworld.NewGreeterClient(conn) reply, err := client.SayHello(context.Background(), &helloworld.HelloRequest{Name: "go-kratos"}) if err != nil { log.Fatal(err) } log.Printf("[grpc] SayHello %+vn", reply) }
运行程序
1.运行etcd,没有安装etcd的请自行百度或gg安装
2.运行服务端
$ cd ./etcd/server $ go run ./main.go INFO msg=[HTTP] server listening on: [::]:8080 INFO msg=[gRPC] server listening on: [::]:9000
3.运行客户端
$ cd ./client $ go run .main.go INFO msg=[resolver] update instances: [{"id":"8fc08b88-e37b-11ec-bb6f-88d7f62323b4","name":"helloworld","version":"","metadata":null,"endpoints":["http://192.168.56.1:8080","grpc://192.168.56.1:9000"]}] 2022/06/04 04:28:21 [http] SayHello message:"welcome go-kratos!" 2022/06/04 04:28:21 [grpc] SayHello message:"welcome go-kratos!" INFO msg=[resolver] update instances: [{"id":"8fc08b88-e37b-11ec-bb6f-88d7f62323b4","name":"helloworld","version":"","metadata":null,"endpoints":["http://192.168.56.1:8080","grpc://192.168.56.1:9000"]}] 2022/06/04 04:28:22 [http] SayHello message:"welcome go-kratos!" 2022/06/04 04:28:22 [grpc] SayHello message:"welcome go-kratos!" 2022/06/04 04:28:23 [http] SayHello message:"welcome go-kratos!" 2022/06/04 04:28:23 [grpc] SayHello message:"welcome go-kratos!" 2022/06/04 04:28:24 [http] SayHello message:"welcome go-kratos!" 2022/06/04 04:28:24 [grpc] SayHello message:"welcome go-kratos!" ... ...
程序运行成功
看看 etcd 运行日志:
2022-06-04 04:26:03.896230 W | wal: sync duration of 1.1565369s, expected less than 1s 2022-06-04 04:26:03.991356 N | embed: serving insecure client requests on 127.0.0.1:2379, this is strongly discouraged! 2022-06-04 04:27:18.187663 W | etcdserver: request "header:<ID:7587862969930594823 > put:<key:"/microservices/helloworld/8fc08b88-e37b-11ec-bb6f-88d7f62323b4" value_size:162 lease:7587862969930594821 >" with result "size:4" took too long (113.4545ms) to execute
2.3 简析服务注册程序
一图解千言:
-
etcdregitry.New(client)
这里是对 etcd client 的包装处理,那么选择的服务中心就是 etcd。也可以使用consul,zookeeper 等,kratos 对它们都有封装。
// 对 etcd client 的包装在处理 r := etcdregitry.New(client) // https://github.com/go-kratos/kratos/contrib/registry/etcd/registry.go#L56 // New creates etcd registry func New(client *clientv3.Client, opts ...Option) (r *Registry) { op := &options{ ctx: context.Background(), namespace: "/microservices", ttl: time.Second * 15, maxRetry: 5, } for _, o := range opts { o(op) } return &Registry{ opts: op, client: client, kv: clientv3.NewKV(client), } }
-
kratos.New()
对应用程序初始化化,应用程序参数初始化 - 默认参数或接受传入的参数。
// https://github.com/go-kratos/kratos/blob/v2.3.1/app.go#L39 func New(opts ...Option) *App { o := options{ ctx: context.Background(), sigs: []os.Signal{syscall.SIGTERM, syscall.SIGQUIT, syscall.SIGINT}, registrarTimeout: 10 * time.Second, stopTimeout: 10 * time.Second, } ... ... return &App{ ctx: ctx, cancel: cancel, opts: o, } }
-
kratos.Name("helloworld")
处理应用的服务参数。这个参数传入到上面
func New(opts ...Option) *App
。
// https://github.com/go-kratos/kratos/options.go#L41 // Name with service name. func Name(name string) Option { return func(o *options) { o.name = name } }
-
kratos.Registrar(r)
选择哪个服务中心(etcd,consul,zookeeper,nacos 等等)作为 kratos 的服务中心。
这个参数传入到上面func New(opts ...Option) *App
。
// https://github.com/go-kratos/kratos/blob/v2.3.1/options.go#L81 func Registrar(r registry.Registrar) Option { return func(o *options) { o.registrar = r } }
- registrar.Register()
真正把服务注册到服务中心的是 app.Run()
这个方法里的 a.opts.registrar.Register()
方法,Register() 方法把服务实例注册到服务中心。
// https://github.com/go-kratos/kratos/app.go#L84 if err := a.opts.registrar.Register(rctx, instance); err != nil { return err }
参数 instance 就是方法 buildInstance() 返回的服务实例 ServiceInstance,ServiceInstance struct 包含了一个服务实例所需的字段。
// https://github.com/go-kratos/kratos/app.go#L154 func (a *App) buildInstance() (*registry.ServiceInstance, error) // https://github.com/go-kratos/kratos/registry/registry.go#L33 type ServiceInstance struct { ID string `json:"id"` Name string `json:"name"` Version string `json:"version"` Metadata map[string]string `json:"metadata"` Endpoints []string `json:"endpoints"` }