Golang之实现一个负载均衡算法（随机，轮询）

package balance

type Balancer interface {
    DoBalance([]*Instance, ...string) (*Instance, error)
}

package balance

import (
    "strconv"
)

type Instance struct {
    host string
    port int
}

func NewInstance(host string, port int) *Instance {
    return &Instance{
        host: host,
        port: port,
    }
}

//定义Instance结构体的方法GetHost()
func (p *Instance) GetHost() string {
    return p.host
}

//定义方法GetPort()
func (p *Instance) GetPort() int {
    return p.port
}
func (p *Instance) String() string {
    return p.host + ":" + strconv.Itoa(p.port)
}

package balance

import "fmt"

type BalanceMgr struct {
    allBalancer map[string]Balancer
}

var mgr = BalanceMgr{
    allBalancer: make(map[string]Balancer),
}

func (p *BalanceMgr) registerBalancer(name string, b Balancer) {
    p.allBalancer[name] = b
}
func RegisterBalancer(name string, b Balancer) {
    mgr.registerBalancer(name, b)
}
func DoBalance(name string, insts []*Instance) (inst *Instance, err error) {
    balancer, ok := mgr.allBalancer[name]
    if !ok {
        err = fmt.Errorf("Not found %s balancer", name)
        return
    }
    fmt.Printf("use %s balancer\n", name)
    inst, err = balancer.DoBalance(insts)
    return
}

package balance

import (
    "errors"
    "math/rand"
)

func init() {
    RegisterBalancer("random", &RandomBalance{})
}

type RandomBalance struct {
}

func (p *RandomBalance) DoBalance(insts []*Instance, key ...string) (inst *Instance, err error) {
    if len(insts) == 0 {
        err = errors.New("No instance")
        return
    }
    lens := len(insts)
    index := rand.Intn(lens)
    inst = insts[index]
    return
}

package balance

import (
    "errors"
)

func init() {
    RegisterBalancer("roundrobin", &RoundRobinBalance{})
}

type RoundRobinBalance struct {
    curIndex int
}

func (p *RoundRobinBalance) DoBalance(insts []*Instance, key ...string) (inst *Instance, err error) {
    if len(insts) == 0 {
        err = errors.New("No instance")
        return
    }
    lens := len(insts)
    if p.curIndex >= lens {
        p.curIndex = 0
    }
    inst = insts[p.curIndex]
    p.curIndex = (p.curIndex + 1) % lens
    return
}

package main

import (
    "fmt"
    "go_dev/day7/example/example1/balance"
    "math/rand"
    "os"
    "time"
)

func main() {
    var insts []*balance.Instance
    for i := 0; i < 16; i++ {
        host := fmt.Sprintf("192.168.%d.%d", rand.Intn(255), rand.Intn(255))
        one := balance.NewInstance(host, 8080)
        insts = append(insts, one)
    }
    var balanceName = "random"
    if len(os.Args) > 1 {
        balanceName = os.Args[1]
    }
    for {
        inst, err := balance.DoBalance(balanceName, insts)
        if err != nil {
            fmt.Println("do balance err:", err)
            fmt.Fprintf(os.Stdout, "do balance err\n")
            continue
        }
        fmt.Println(inst)
        time.Sleep(time.Second)
    }
}

package main

import (
    "fmt"
    "go_dev/day7/example/example1/balance"
    "hash/crc32"
    "math/rand"
)

type HashBalance struct {
    Name string
    Age  int
}

func init() {
    balance.RegisterBalancer("hash", &HashBalance{})
}
func (p *HashBalance) DoBalance(insts []*balance.Instance, key ...string) (inst *balance.Instance, err error) {
    var defKey string = fmt.Sprintf("%d", rand.Int())
    if len(key) > 0 {
        defKey = key[0]
    }
    lens := len(insts)
    if lens == 0 {
        err = fmt.Errorf("No backend instance")
        return
    }
    crcTable := crc32.MakeTable(crc32.IEEE)
    hashVal := crc32.Checksum([]byte(defKey), crcTable)
    index := int(hashVal) % lens
    inst = insts[index]
    return
}