grpc-lb采用客户端进程内负载均衡方式，支持随机、轮询、一致性哈希三种负载均衡策略，并支持服务端权重。可采用etcd或consul作为注册中心。

项目地址：
https://github.com/liyue201/g...

基本架构如图，服务提供者起来后向注册中心注册自己的信息，ip、端口、权重等，并保持心跳。客户端监听注册中心，获取服务器列表，一旦服务器发生变化，客户端马上更新本地的服务器列表。客户端每个请求都通过负载均衡策略选择一个合适的服务器去访问。

随机负载均衡客户端例子：

package main

import (
    etcd "gIThub.COM/coreos/etcd/client"
    grpclb "github.com/liyue201/grpc-lb"
    "github.com/liyue201/grpc-lb/examples/PRoto"
    registry "github.com/liyue201/grpc-lb/registry/etcd"
    "golang.org/x/net/context"
    "GOOGLE.golang.org/grpc"
    "LOG"
)

func main() {
    etcdConfg := etcd.config{
        Endpoints: []string{"http://120.24.44.201:4001"},
    }
    r := registry.NewResolver("/grpc-lb", "test", etcdConfg)
    b := grpclb.NewBalancer(r, grpclb.NewRandomSelector())
    c, err := grpc.Dial("", grpc.WithInsecure(), grpc.WithBalancer(b))
    if err != nil {
        log.Printf("grpc dial: %s", err)
        return
    }
    defer c.Close()

    client := proto.NewTestClient(c)
    resp, err := client.Say(context.Background(), &proto.SayReq{Content: "random"})
    if err != nil {
        log.Println(err)
        return
    }
    log.Printf(resp.Content)
}

轮询负载均衡，只需把NewRandomSelector改成NewRoundRobinSelector即可。

package main

import (
    etcd "github.com/coreos/etcd/client"
    grpclb "github.com/liyue201/grpc-lb"
    "github.com/liyue201/grpc-lb/examples/proto"
    registry "github.com/liyue201/grpc-lb/registry/etcd"
    "golang.org/x/net/context"
    "google.golang.org/grpc"
    "log"
)

func main() {
    etcdConfg := etcd.Config{
        Endpoints: []string{"http://120.24.44.201:4001"},
    }
    r := registry.NewResolver("/grpc-lb", "test", etcdConfg)
    b := grpclb.NewBalancer(r, grpclb.NewRoundRobinSelector())
    c, err := grpc.Dial("", grpc.WithInsecure(), grpc.WithBalancer(b))
    if err != nil {
        log.Printf("grpc dial: %s", err)
        return
    }
    defer c.Close()

    client := proto.NewTestClient(c)
    resp, err := client.Say(context.Background(), &proto.SayReq{Content: "round robin"})
    if err != nil {
        log.Println(err)
        return
    }
    log.Printf(resp.Content)

}

一致性哈希负载均衡，需要给每个请求传一个哈希的参数，这个根据应用场景而定，就是下面这个例子中的hashData。

package main

import (
    "fmt"
    etcd "github.com/coreos/etcd/client"
    grpclb "github.com/liyue201/grpc-lb"
    "github.com/liyue201/grpc-lb/examples/proto"
    registry "github.com/liyue201/grpc-lb/registry/etcd"
    "golang.org/x/net/context"
    "google.golang.org/grpc"
    "log"
    "time"
)

func main() {
    etcdConfg := etcd.Config{
        Endpoints: []string{"http://120.24.44.201:4001"},
    }
    r := registry.NewResolver("/grpc-lb", "test", etcdConfg)
    b := grpclb.NewBalancer(r, grpclb.NewKetamaSelector(grpclb.DefaultKetamaKey))
    c, err := grpc.Dial("", grpc.WithInsecure(), grpc.WithBalancer(b), grpc.WithTimeout(time.Second))
    if err != nil {
        log.Printf("grpc dial: %s", err)
        return
    }
    client := proto.NewTestClient(c)

    for i := 0; i < 10; i++ {
        ctx := context.Background()

        hashData := fmt.Sprintf("aaaa %d", i)
        resp, err := client.Say(context.WithValue(ctx, grpclb.DefaultKetamaKey, hashData),
            &proto.SayReq{Content: "ketama"})
        if err != nil {
            log.Println(err)
            time.Sleep(time.Second)
            continue
        }
        log.Printf(resp.Content)
        time.Sleep(time.Second)
    }
}

服务端的代码如下， 使用以下命令运行3个服务进程，再启动客户端。
go run main.go -node node1 -port 28544
go run main.go -node node2 -port 18562
go run main.go -node node3 -port 27772

package main

import (
    "flag"
    "fmt"
    etcd "github.com/coreos/etcd/client"
    "github.com/liyue201/grpc-lb/examples/proto"
    registry "github.com/liyue201/grpc-lb/registry/etcd"
    "golang.org/x/net/context"
    "google.golang.org/grpc"
    "log"
    "net"
    "sync"
    "time"
)

VAR nodeiD = flag.String("node", "node1", "node ID")
var port = flag.Int("port", 8080, "listening port")

type RpcServer struct {
    addr string
    s    *grpc.Server
}

func NewRpcServer(addr string) *RpcServer {
    s := grpc.NewServer()
    rs := &RpcServer{
        addr: addr,
        s:    s,
    }
    return rs
}

func (s *RpcServer) Run() {
    listener, err := net.Listen("tcp", s.addr)
    if err != nil {
        log.Printf("failed to listen: %v", err)
        return
    }
    log.Printf("rpc listening on:%s", s.addr)

    proto.RegisterTestServer(s.s, s)
    s.s.Serve(listener)
}

func (s *RpcServer) Stop() {
    s.s.GracefulStop()
}

func (s *RpcServer) Say(ctx context.Context, req *proto.SayReq) (*proto.SayResp, error) {
    text := "Hello " + req.Content + ", I am " + *nodeID
    log.Println(text)

    return &proto.SayResp{Content: text}, nil
}

func StartService() {
    etcdConfg := etcd.Config{
        Endpoints: []string{"http://120.24.44.201:4001"},
    }

    registry, err := registry.NewRegistry(
        registry.Option{
            EtcdConfig:  etcdConfg,
            RegistryDir: "/grpc-lb",
            ServiceName: "test",
            NodeID:      *nodeID,
            NData: registry.NodeData{
                Addr: fmt.Sprintf("127.0.0.1:%d", *port),
                //Metadata: map[string]string{"weight": "1"}, //这里配置权重，不配置默认是1
            },
            TTL: 10 * time.Second,
        })
    if err != nil {
        log.Panic(err)
        return
    }
    server := NewRpcServer(fmt.Sprintf("0.0.0.0:%d", *port))
    wg := sync.WaitGroup{}

    wg.Add(1)
    go func() {
        server.Run()
        wg.Done()
    }()

    wg.Add(1)
    go func() {
        registry.Register()
        wg.Done()
    }()

    //stop the server after one minute
    //go func() {
    //    time.Sleep(time.Minute)
    //    server.Stop()
    //    registry.Deregister()
    //}()

    wg.Wait()
}

//go run main.go -node node1 -port 28544
//go run main.go -node node2 -port 18562
//go run main.go -node node3 -port 27772
func main() {
    flag.Parse()
    StartService()
}