docs: add explain

Author: coderi421

gmicro/registry/consul/registry.go

@@ -231,14 +231,15 @@ func (r *Registry) resolve(ctx context.Context, ss *serviceSet) error {
 	}
 
 	go func() {
+		// 长轮询的思想: 如果服务有变化, 则立即返回, 否则等待一段时间后返回, 以减少请求次数
 		ticker := time.NewTicker(time.Second)
 		defer ticker.Stop()
 		for {
 			select {
 			case <-ticker.C:
-				timeoutCtx, cancel := context.WithTimeout(context.Background(), r.timeout)
-				tmpService, tmpIdx, err := r.cli.Service(timeoutCtx, ss.serviceName, idx, true)
-				cancel()
+				timeoutContext, c := context.WithTimeout(context.Background(), r.timeout)
+				tmpService, tmpIdx, err := r.cli.Service(timeoutContext, ss.serviceName, idx, true)
+				c()
 				if err != nil {
 					time.Sleep(time.Second)
 					continue

gmicro/server/rpcserver/client.go

@@ -130,7 +130,7 @@ func dial(ctx context.Context, insecure bool, opts ...ClientOption) (*grpc.Clien
 		grpc.WithChainStreamInterceptor(streamInts...),
 	}
 
-	//服务发现的选项
+	//服务发现的选项 这里调用 resolver 的直连模式或者是服务发现模式
 	if &options.discovery != nil {
 		grpcOpts = append(grpcOpts, grpc.WithResolvers(
 			discovery.NewBuilder(options.discovery,

gmicro/server/rpcserver/resolver/discovery/resolver.go

@@ -26,6 +26,7 @@ type discoveryResolver struct {
 }
 
 func (r *discoveryResolver) watch() {
+	// 轮询监听
 	for {
 		select {
 		case <-r.ctx.Done():