go-kit 服务发现(3) etcd

基本使用

注册

//Etcd客户端
client, _ := etcdv3.NewClient(context.Background(),[]string{"http://localhost:2379"},etcdv3.ClientOptions{})

//注册器
register := etcdv3.NewRegistrar(client,etcdv3.Service{
	Key: "/services/hello/",
	Value: "http://127.0.0.1:8080",
},logger)
register.Register()
defer register.Deregister()

发现

//Etcd客户端
client,_ := etcdv3.NewClient(context.Background(),[]string{"http://localhost:2379"},etcdv3.ClientOptions{})

//服务实例
instancer , _ := etcdv3.NewInstancer(client,"/services/hello/",logger)

底层原理

目录结构

.
├── client.go 客户端
├── doc.go
├── example_test.go
├── instancer.go 服务实例
├── instancer_test.go
├── integration_test.go
├── registrar.go 注册器
└── registrar_test.go

目录中主要的是这三个文件，client.go instancer.go registrar.go

client.go

type Client interface {
	//获取一组value通过key前缀
	GetEntries(prefix string) ([]string, error)
	//watch指定前缀的key
	WatchPrefix(prefix string, ch chan struct{})
	//注册服务
	Register(s Service) error
	//注销服务
	Deregister(s Service) error
	//etcd 
	LeaseID() int64
}

type client struct {
	//etcd客户端使用v3版本api
	cli *clientv3.Client
	ctx context.Context
	//etcd key/value 操作实例
	kv clientv3.KV
	// etcd watcher 操作实例
	watcher clientv3.Watcher
	// watcher context
	wctx context.Context
	// watcher cancel func
	wcf context.CancelFunc
	// leaseID will be 0 (clientv3.NoLease) if a lease was not created
	leaseID clientv3.LeaseID

	//etcdKeepAlive实现心跳检测
	hbch <-chan *clientv3.LeaseKeepAliveResponse
	// etcd Lease 操作实例
	leaser clientv3.Lease
}
func NewClient(ctx context.Context, machines []string, options ClientOptions) (Client, error)

主要包含以下6个函数

• NewClient 创建etcd客户端，赋值给 client.cli
• GetEntries 通过 client.kv 获取value
• WatchPrefix 通过 client.watcher 监听key
• Deregister 通过 client.cli 服务绑定的key
• LeaseID return client.leaseID
• Register
  • 初始化 client.leaser
  • 初始化 client.watcher
  • 初始化 client.kv
  • 通过 client.kv 操作写入etcd，服务注册的key和value
  • 创建 client.leaseID，默认心跳3秒，lease TTL9秒
  • client.leaser调用KeepAlive

registrar.go

type Registrar struct {
	//etcd客户端
	client  Client
	//注册的服务
	service Service
	logger  log.Logger

	//服务Deregister并发锁
	quitmtx sync.Mutex
	//服务退出通道
	quit    chan struct{}
}

//服务的key和地址
type Service struct {
	Key   string // unique key, e.g. "/service/foobar/1.2.3.4:8080"
	Value string // returned to subscribers, e.g. "http://1.2.3.4:8080"
	TTL   *TTLOption
}

//服务心跳检测
type TTLOption struct {
	heartbeat time.Duration // e.g. time.Second * 3
	ttl       time.Duration // e.g. time.Second * 10
}

func NewTTLOption(heartbeat, ttl time.Duration) *TTLOption 
func NewRegistrar(client Client, service Service, logger log.Logger) *Registrar
func (r *Registrar) Register()
func (r *Registrar) Deregister()

主要包含以下4个函数

• NewTTLOption 心跳检测参数
• NewRegistrar 创建 Registrar
• Register 调用 client.go中 Register 方法
• Deregister 调用 client.go中 Deregister 方法

instancer.go

type Instancer struct {
  //实例缓存
	cache  *instance.Cache
	//etcd客户端
	client Client
	//实例前缀
	prefix string
	logger log.Logger
	//Instancer 主动退出 通道
	quitc  chan struct{}
}

func NewInstancer(c Client, prefix string, logger log.Logger) (*Instancer, error) 
func (s *Instancer) loop() 
func (s *Instancer) Stop()
func (s *Instancer) Register(ch chan<- sd.Event) 
func (s *Instancer) Deregister(ch chan<- sd.Event)

主要包含以下5个函数

• NewInstancer
  • 调用 client.go GetEntries函数，获取对应的一组服务地址
  • 查询到的服务地址写入缓存 Instancer.cache
• loop
  • 监听服务对应的key
• Stop
  • 关闭服务监听
• Register
• Deregister