hello-go/grpc-demo/clientImpl/example_resolver.go

package clientImpl

import (
	"../constants"
	"google.golang.org/grpc/resolver"
)

// resolver工厂实现类

type ExampleResolverBuilder struct{}

func (*ExampleResolverBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) {
	r := &exampleResolver{
		target: target,
		cc:     cc,
		addressStore: map[string][]string{
			constants.ExampleServiceName: constants.ExampleEndpoints, // 服务命名与实际服务终结点列表的对应关系 "go-example": ["localhost:50051", "localhost:50052"]
		},
	}
	r.start()
	return r, nil
}
func (*ExampleResolverBuilder) Scheme() string { return constants.ExampleScheme } // "grpc"

// resolver实现类

type exampleResolver struct {
	target       resolver.Target
	cc           resolver.ClientConn
	addressStore map[string][]string
}

func (r *exampleResolver) start() {
	addrList := r.addressStore[r.target.Endpoint]
	addresses := make([]resolver.Address, len(addrList))
	for i, s := range addrList {
		addresses[i] = resolver.Address{Addr: s}
	}
	r.cc.UpdateState(resolver.State{Addresses: addresses})
}
func (*exampleResolver) ResolveNow(resolver.ResolveNowOptions) {}
func (*exampleResolver) Close()                                {}