add some comment

Author: Verthandii

middleware/melody-etcd/client.go

@@ -100,6 +100,7 @@ func NewClient(ctx context.Context, machines []string, options ClientOptions) (C
 
 // GetEntries implements the etcd Client interface.
 func (c *client) GetEntries(key string) ([]string, error) {
+	// TODO: bug 如果没有先启动 etcd 这里就会崩掉 并且卡住之后的endpoint的初始化
 	resp, err := c.v3.Get(c.ctx, key, clientv3.WithPrefix())
 	if err != nil {
 		return nil, err

middleware/melody-etcd/subscriber.go

@@ -2,6 +2,7 @@ package etcd
 
 import (
 	"context"
+	"errors"
 	"melody/config"
 	"melody/sd"
 	"sync"
@@ -11,6 +12,7 @@ var (
 	subscribers               = map[string]sd.Subscriber{}
 	subscribersMutex          = &sync.Mutex{}
 	fallbackSubscriberFactory = sd.FixedSubscriberFactory
+	NoClientError             = errors.New("errors: no SD client")
 )
 
 // SubscriberFactory builds a an etcd subscriber SubscriberFactory with the received etcd client
@@ -57,6 +59,10 @@ func NewSubscriber(ctx context.Context, c Client, prefix string) (*Subscriber, e
 		mutex:  &sync.RWMutex{},
 	}
 
+	if s.client == nil {
+		return nil, NoClientError
+	}
+
 	// 获取 key 为 s.prefix 的所有value
 	instances, err := s.client.GetEntries(s.prefix)
 	if err != nil {

proxy/factory.go

@@ -55,7 +55,7 @@ func (d defaultFactory) New(cfg *config.EndpointConfig) (p Proxy, err error) {
 func (d defaultFactory) NewStack(backend *config.Backend) (p Proxy) {
 	// 根据config.Backend定制backendProxy 执行顺序：④
 	p = d.backendFactory(backend)
-	// 均衡中间件注册                     执行顺序：③
+	// 均衡中间件注册(在此处调用对应的服务发现)     执行顺序：③
 	p = NewLoadBalancedMiddlewareWithSubscriber(d.subscriberFactory(backend))(p)
 	if backend.ConcurrentCalls > 1 {
 		// 并发调用 > 1                    执行顺序：②

sd/register.go

@@ -10,7 +10,7 @@ func RegisterSubscriberFactory(name string, sf SubscriberFactory) error {
 	return subscriberFactories.Register(name, sf)
 }
 
-// GetSubscriber returns a subscriber from package register
+// GetSubscriber 在此处选择调用哪种服务发现
 func GetSubscriber(cfg *config.Backend) Subscriber {
 	return subscriberFactories.Get(cfg.SD)(cfg)
 }