gRPC之grpc负载均衡(resolver)

1、grpc负载均衡(resolver)

1.1 proto编写和编译

syntax = "proto3";

option go_package = "./;echo";

package echo;

message EchoRequest {
    string message = 1;
}

message EchoResponse {
    string message = 1;
}

service Echo {
    rpc UnaryEcho(EchoRequest) returns (EchoResponse) {}
}

$ protoc -I . --go_out=plugins=grpc:. ./echo.proto

1.2 服务端

package main

import (
	"context"
	pb "demo/pb"
	"fmt"
	"google.golang.org/grpc"
	"log"
	"net"
	"sync"
)

var (
	addrs = []string{":50051", ":50052"}
)

type ecServer struct {
	pb.UnimplementedEchoServer
	addr string
}

func (s *ecServer) UnaryEcho(ctx context.Context, req *pb.EchoRequest) (*pb.EchoResponse, error) {
	return &pb.EchoResponse{Message: fmt.Sprintf("%s (from %s)", req.Message, s.addr)}, nil
}

func startServer(addr string) {
	lis, err := net.Listen("tcp", addr)
	if err != nil {
		log.Fatalf("failed to listen: %v", err)
	}
	s := grpc.NewServer()
	pb.RegisterEchoServer(s, &ecServer{addr: addr})
	log.Printf("serving on %s\n", addr)
	if err := s.Serve(lis); err != nil {
		log.Fatalf("failed to serve: %v", err)
	}
}

func main() {
	var wg sync.WaitGroup
	for _, addr := range addrs {
		wg.Add(1)
		go func(addr string) {
			defer wg.Done()
			startServer(addr)
		}(addr)
	}
	wg.Wait()
}

1.3 客户端

package main

import (
	"context"
	ecpb "demo/pb"
	"fmt"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials/insecure"
	"google.golang.org/grpc/resolver"
	"log"
	"time"
)

const (
	exampleScheme      = "example"
	exampleServiceName = "lb.example.grpc.io"
)

var addrs = []string{"localhost:50051", "localhost:50052"}

func callUnaryEcho(c ecpb.EchoClient, message string) {
	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()
	r, err := c.UnaryEcho(ctx, &ecpb.EchoRequest{Message: message})
	if err != nil {
		log.Fatalf("could not greet: %v", err)
	}
	fmt.Println(r.Message)
}

func makeRPCs(cc *grpc.ClientConn, n int) {
	hwc := ecpb.NewEchoClient(cc)
	for i := 0; i < n; i++ {
		callUnaryEcho(hwc, "this is examples/load_balancing")
	}
}

func main() {
	// "pick_first" is the default, so there's no need to set the load balancing policy.
	pickfirstConn, err := grpc.Dial(
		fmt.Sprintf("%s:///%s", exampleScheme, exampleServiceName),
		grpc.WithTransportCredentials(insecure.NewCredentials()),
	)
	if err != nil {
		log.Fatalf("did not connect: %v", err)
	}
	defer pickfirstConn.Close()
	fmt.Println("--- calling helloworld.Greeter/SayHello with pick_first ---")
	makeRPCs(pickfirstConn, 10)

	fmt.Println()

	// Make another ClientConn with round_robin policy.
	roundrobinConn, err := grpc.Dial(
		fmt.Sprintf("%s:///%s", exampleScheme, exampleServiceName),
		// This sets the initial balancing policy.
		grpc.WithDefaultServiceConfig(`{"loadBalancingConfig": [{"round_robin":{}}]}`),
		grpc.WithTransportCredentials(insecure.NewCredentials()),
	)
	if err != nil {
		log.Fatalf("did not connect: %v", err)
	}
	defer roundrobinConn.Close()

	fmt.Println("--- calling helloworld.Greeter/SayHello with round_robin ---")
	makeRPCs(roundrobinConn, 10)
}

// Following is an example name resolver implementation. Read the name
// resolution example to learn more about it.

type exampleResolverBuilder struct{}

func (*exampleResolverBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) {
	r := &exampleResolver{
		target: target,
		cc:     cc,
		addrsStore: map[string][]string{
			exampleServiceName: addrs,
		},
	}
	r.start()
	return r, nil
}
func (*exampleResolverBuilder) Scheme() string { return exampleScheme }

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

func (r *exampleResolver) start() {
	// r.target.Endpoint(): lb.example.grpc.io
	addrStrs := r.addrsStore[r.target.Endpoint()]
	// len(addrStrs): 2
	addrs := make([]resolver.Address, len(addrStrs))
	for i, s := range addrStrs {
		addrs[i] = resolver.Address{Addr: s}
	}
	r.cc.UpdateState(resolver.State{Addresses: addrs})
}

func (*exampleResolver) ResolveNow(o resolver.ResolveNowOptions) {}

func (*exampleResolver) Close() {}

func init() {
	resolver.Register(&exampleResolverBuilder{})
}

1.4 测试

[root@zsx demo]# go run server/server.go
2023/02/17 18:32:59 serving on :50052
2023/02/17 18:32:59 serving on :50051

[root@zsx demo]# go run client/client.go
--- calling helloworld.Greeter/SayHello with pick_first ---
this is examples/load_balancing (from :50051)
this is examples/load_balancing (from :50051)
this is examples/load_balancing (from :50051)
this is examples/load_balancing (from :50051)
this is examples/load_balancing (from :50051)
this is examples/load_balancing (from :50051)
this is examples/load_balancing (from :50051)
this is examples/load_balancing (from :50051)
this is examples/load_balancing (from :50051)
this is examples/load_balancing (from :50051)

--- calling helloworld.Greeter/SayHello with round_robin ---
this is examples/load_balancing (from :50051)
this is examples/load_balancing (from :50052)
this is examples/load_balancing (from :50051)
this is examples/load_balancing (from :50052)
this is examples/load_balancing (from :50051)
this is examples/load_balancing (from :50052)
this is examples/load_balancing (from :50051)
this is examples/load_balancing (from :50052)
this is examples/load_balancing (from :50051)
this is examples/load_balancing (from :50052)

# 项目结构
[root@zsx protoc]# tree demo/
demo/
├── client
│   └── client.go
├── go.mod
├── go.sum
├── pb
│   ├── echo.pb.go
│   └── echo.proto
└── server
    └── server.go

3 directories, 6 files

参考地址：

• https://godoc.org/google.golang.org/grpc/balancer
• https://github.com/grpc/grpc/blob/master/doc/service_config.md