golang实现负载均衡算法

package main

import (
    "fmt"
    "log"
    "net/http"
    "os"
    "os/signal"
    "strconv"
    "syscall"
    "time"
)

type realServer struct {
    Addr string
}

func (rs *realServer) HelloHandler(w http.ResponseWriter,r *http.Request){
    data := fmt.Sprintf("[%s] http://%s%s \n\n",rs.Addr,rs.Addr,r.RequestURI)
    w.Write([]byte(data))
}

func (rs *realServer) Run(){
    fmt.Println("Http server tart to serve at :",rs.Addr)
    mux := http.NewServeMux()
    mux.HandleFunc("/",rs.HelloHandler)
    server := &http.Server{
        Addr: rs.Addr,
        Handler: mux,
        WriteTimeout: time.Second * 3,
    }
    go func(){
        if err := server.ListenAndServe();err != nil{
            log.Fatal("Start http server failed,err:",err)
        }
    }()
}

func main() {
    doneCh := make(chan os.Signal)

    for i:=0;i<5;i++{
        port := "808" + strconv.Itoa(i)
        addr := "127.0.0.1:" + port
        rs := &realServer{Addr: addr}
        go rs.Run()

    }

    signal.Notify(doneCh,syscall.SIGINT,syscall.SIGTERM)
    <- doneCh
}

2、反向代理代码框架

// 
package httpServer

import (
    "math/rand"
    "time"
)

type HttpServer struct {
    Host string
}

type LoadBalance struct {
    Servers []*HttpServer
}

func NewLoadBalance()*LoadBalance{
    return &LoadBalance{Servers:make([]*HttpServer,0)}
}

func NewHttpServer(host string)*HttpServer{
    return &HttpServer{
        Host:host,
    }
}

func (lb *LoadBalance)Add(server *HttpServer){
    lb.Servers = append(lb.Servers,server)
}

启动服务

// server.go
package main

import (
    "log"
    "net/http"
    "net/http/httputil"
    "net/url"
    . "gostudy/reverseProxyDemo/httpServer"
)

type ReveseProxyHandler struct {

}

func (rph *ReveseProxyHandler)ServeHTTP(w http.ResponseWriter,r *http.Request){
    lb := NewLoadBalance()
    lb.Add(NewHttpServer("http://127.0.0.1:8080"))
    lb.Add(NewHttpServer("http://127.0.0.1:8081"))
    lb.Add(NewHttpServer("http://127.0.0.1:8082"))
    lb.Add(NewHttpServer("http://127.0.0.1:8083"))
    lb.Add(NewHttpServer("http://127.0.0.1:8084"))

    url,err := url.Parse(lb.GetHttpServerByRandom().Host)
    if err != nil {
        log.Println("[ERR] url.Parse failed,err:",err)
        return
    }
    proxy := httputil.NewSingleHostReverseProxy(url)
    proxy.ServeHTTP(w,r)

}

func main() {
    proxy := &ReveseProxyHandler{}

    log.Println("Start to serve at 127.0.0.1:8888")
    if err := http.ListenAndServe(":8888",proxy);err !=nil{
        log.Fatal("Failed to start reverse proxy server ,err:",err)
    }
}

3、随机负载均衡算法

// httpServer/reverseProxy.go
// 随机负载均衡
func (lb *LoadBalance)GetHttpServerByRandom()*HttpServer{
    rand.Seed(time.Now().UnixNano())
    index := rand.Intn(len(lb.Servers))
    return lb.Servers[index]
}

测试结果

$ for i in {0..9};do curl -s http://127.0.0.1:8888/reverseproxydemo?id=123;done
[127.0.0.1:8083] http://127.0.0.1:8083/reverseproxydemo?id=123
[127.0.0.1:8084] http://127.0.0.1:8084/reverseproxydemo?id=123
[127.0.0.1:8082] http://127.0.0.1:8082/reverseproxydemo?id=123
[127.0.0.1:8080] http://127.0.0.1:8080/reverseproxydemo?id=123
[127.0.0.1:8081] http://127.0.0.1:8081/reverseproxydemo?id=123
[127.0.0.1:8082] http://127.0.0.1:8082/reverseproxydemo?id=123
[127.0.0.1:8080] http://127.0.0.1:8080/reverseproxydemo?id=123
[127.0.0.1:8081] http://127.0.0.1:8081/reverseproxydemo?id=123
[127.0.0.1:8080] http://127.0.0.1:8080/reverseproxydemo?id=123
[127.0.0.1:8084] http://127.0.0.1:8084/reverseproxydemo?id=123

加权随机

原理：获取到所有节点的权重值，将weight个当前节点Index加到一个[]int，并随机从中获取一个index，例如：
A ： B ： C = 5:2:1 且ABC三个节点的Index分别为0,1,2，那么新建一个如下是切片：
[]int{0,0,0,0,0,1,1,2} ，然后通过rand(len([]int)) 随机拿到一个index

// httpserver.go
type HttpServer struct {
    Host string
    Weight int
}

func NewHttpServer(host string,weight int)*HttpServer{
    return &HttpServer{
        Host:host,
        Weight:weight,
    }
}

// 加权随机
func (lb *LoadBalance)GetHttpServerByRandomWithWeight(httpServerArr []int)*HttpServer{
    rand.Seed(time.Now().UnixNano())
    index := rand.Intn(len(httpServerArr))
    return lb.Servers[httpServerArr[index]]
}

// loadBalanceDemo/loadbalance.go
// 加权随机
    var httpServerArr []int
    for index,server := range lb.Servers{
        if server.Weight > 0 {
            for i:=0;i<server.Weight;i++{
                httpServerArr = append(httpServerArr,index)
            }
        }
    }

    url,err := url.Parse(lb.GetHttpServerByRandomWithWeight(httpServerArr).Host)

加权随机算法优化版

上面的加权随机算法实现起来比较简单，但存在一个明显弊端，如果weight值的大小将直接影响切片大小，例如5:2 跟 50000:20000 本质上是一样的，但后者将占用更多的内存空间。因此我们需要对该算法做下优化，将N个节点权重计算出N个区间，然后取随机数rand(weightSum)，看该数落在哪个区间就返回该区间对应的index值，举个例子：
假设A:B:C = 5:2:1
那么我们先计算出3个区间：5,7(5+2),8(5+2+1)
[0,5) [5,7) [7,8)
然后取rand(5+2+1)，假设获取到的值为6，则落在[5,7) 这个区间，返回index=1
可以看出rand(7)随机数落在各个区间分布如下：
[0,5) ： 0,1,2,3,4
[5,7) ：5,6
[7,8) ：7
正好是5:2:1

下面是具体实现：

// 加权随机优化版
func (lb *LoadBalance)GetHttpServerByRandomWithWeight2()*HttpServer{
    rand.Seed(time.Now().UnixNano())
    // 计算所有节点权重值之和
    weightSum := 0
    for i:=0;i<len(lb.Servers);i++{
        weightSum += lb.Servers[i].Weight
    }
    // 随机数获取
    randNum := rand.Intn(weightSum)

    sum := 0
    for i := 0;i<len(lb.Servers);i++{
        sum += lb.Servers[i].Weight
        // 因为区间是[ ) ，左闭右开，故随机数小于当前权重sum值，则代表落在该区间，返回当前的index
        if randNum < sum {
            return lb.Servers[i]
        }
    }
    return lb.Servers[0]
}

轮询算法

假设有ABC 3台机器，那么请求过来将按照ABCABC 这样的顺顺序将请求反向代理到后端服务器

原理是记录当前的index值，每次请求+1 取模（这里仅演示算法，未考虑线程安全问题，没有加锁）

// loadbalance.go
// 由于每次请求需要保存当前的index值，所以使用全局变量lb，并在初始化函数中初始化lb实例
var lb *LoadBalance

func init(){
    lb = NewLoadBalance()
}

// httpserver.go
// 结构体中加上当前index值
type LoadBalance struct {
    Index int
    Servers []*HttpServer
}

// 轮询
func (lb *LoadBalance)GetHttpServerByRoundRobin() *HttpServer{
    server := lb.Servers[lb.Index]
    lb.Index = (lb.Index + 1)% len(lb.Servers)
    return server
}

加权轮询算法-切片算法

/ 加权轮询
func (lb *LoadBalance)GetHttpServerByRoundRobinWithWeight(indexArr []int) *HttpServer{
    lb.Index = (lb.Index + 1)% len(indexArr)
    fmt.Println(indexArr)
    return lb.Servers[indexArr[lb.Index]]
}

package main

import (
    "log"
    "net/http"
    "net/http/httputil"
    "net/url"
    . "loadBalanceDemo/httpServer"
)

type ReveseProxyHandler struct {

}

var lb *LoadBalance
var indexArr []int

func init(){
    lb = NewLoadBalance()

    lb.Add(NewHttpServer("http://127.0.0.1:8082",5))
    lb.Add(NewHttpServer("http://127.0.0.1:8083",2))
    lb.Add(NewHttpServer("http://127.0.0.1:8084",1))

    // 加权轮询
    indexArr = make([]int,0)
    for index,server := range lb.Servers{
        if server.Weight > 0{
            for i:=0;i<server.Weight;i++{
                indexArr = append(indexArr,index)
            }
        }
    }
}

func (rph *ReveseProxyHandler)ServeHTTP(w http.ResponseWriter,r *http.Request){

 // 浏览器访问时默认会请求/favicon.ico，这里忽略该URL
    if r.URL.Path == "/favicon.ico"{
        return
    }
    url,err := url.Parse(lb.GetHttpServerByRoundRobinWithWeight(indexArr).Host)

    if err != nil {
        log.Println("[ERR] url.Parse failed,err:",err)
        return
    }
    proxy := httputil.NewSingleHostReverseProxy(url)
    proxy.ServeHTTP(w,r)

}

func main() {
    proxy := &ReveseProxyHandler{}

    log.Println("Start to serve at 127.0.0.1:8888")
    if err := http.ListenAndServe(":8888",proxy);err !=nil{
        log.Fatal("Failed to start reverse proxy server ,err:",err)
    }
}

加权轮询算法-区间算法

// 加权轮询区间算法
func (lb *LoadBalance)GetHttpServerByRoundRobinWithWeight2()*HttpServer{
    server := lb.Servers[0]
    sum := 0

    for i:=0;i<len(lb.Servers);i++{
        sum += lb.Servers[i].Weight
        if lb.Index < sum{
            server = lb.Servers[i]
            if lb.Index == sum -1 && i != len(lb.Servers)-1{
                lb.Index++
            }else{
                lb.Index = (lb.Index+1) % sum
            }
            fmt.Println(lb.Index)
            break
        }
    }
    return server
}

ip_hash 算法

// ip_hash
// 对客户端IP 做hash 取模得到有一个固定的index，返回固定的httpserver
func (lb *LoadBalance)GetHttpServerByIpHash(ip string) *HttpServer{
    index := int(crc32.ChecksumIEEE([]byte(ip))) % len(lb.Servers)
    return lb.Servers[index]
}

// server.go
// ip_hash
// 传入客户端IP
    url,err := url.Parse(lb.GetHttpServerByIpHash(r.RemoteAddr).Host)

url_hash 算法

// url_hash
    url,err := url.Parse(lb.GetHttpServerByUrlHash(r.RequestURI).Host)

// url_hash
func (lb *LoadBalance) GetHttpServerByUrlHash(url string) *HttpServer{
    index := int(crc32.ChecksumIEEE([]byte(url))) % len(lb.Servers)
    return lb.Servers[index]
}