go 语言 负载均衡 为反向代理添加负载均衡 拓展ReverseProxy

随机负载

package random

import (
	"errors"
	"math/rand"
)

type RandomBalance struct {
	//当前索引
	curIndex int
	//存储负载均衡的地址
	rss []string
	//观察主体
	//conf LoadBalanceConf
}

func (r *RandomBalance) Add(params ...string) error {
	if len(params) == 0 {
		return errors.New("param len 1 at least")
	}
	addr := params[0]
	r.rss = append(r.rss, addr)
	return nil
}

// Next 随机到下一个index
func (r *RandomBalance) Next() string {
	if len(r.rss) == 0 {
		return ""
	}
	r.curIndex = rand.Intn(len(r.rss))
	return r.rss[r.curIndex]
}

// Get 拿到下一个地址
func (r *RandomBalance) Get(key string) (string, error) {
	return r.Next(), nil
}

轮询负载

package round

import "errors"

type RoundRobinBalance struct {
	curIndex int
	rss      []string
	//观察主体
	//conf LoadBalanceConf
}

func (r *RoundRobinBalance) Add(params ...string) error {
	if len(params) == 0 {
		return errors.New("param len 1 at least")
	}
	addr := params[0]
	r.rss = append(r.rss, addr)
	return nil
}

func (r *RoundRobinBalance) Next() string {
	if len(r.rss) == 0 {
		return ""
	}
	lens := len(r.rss)
	if r.curIndex >= lens {
		r.curIndex = 0
	}
	curAddr := r.rss[r.curIndex]
	r.curIndex = (r.curIndex + 1) % lens
	return curAddr
}

func (r *RoundRobinBalance) Get(key string) (string, error) {
	return r.Next(), nil
}

加权负载

package weight

import (
	"errors"
	"strconv"
)

type WeightRoundRobinBalance struct {
	curIndex int
	rss      []*WeightNode
	rsw      []int
	//观察主体
	//conf LoadBalanceConf

}

type WeightNode struct {
	addr            string
	weight          int //权重值
	currentWeight   int //节点当前权重
	effectiveWeight int //有效权重
}

func (r *WeightRoundRobinBalance) Add(params ...string) error {
	if len(params) != 2 {
		return errors.New("param len need 2")
	}
	parInt, err := strconv.ParseInt(params[1], 10, 64)
	if err != nil {
		return err
	}
	node := &WeightNode{addr: params[0], weight: int(parInt)}
	node.effectiveWeight = node.weight
	r.rss = append(r.rss, node)
	return nil
}

func (r *WeightRoundRobinBalance) Next() string {
	total := 0
	var best *WeightNode
	for i := 0; i < len(r.rss); i++ {
		w := r.rss[i]
		//step 1 统计所以有效权重之和
		total += w.effectiveWeight
		//step 2 变更节点 临时权重
		w.currentWeight += w.effectiveWeight

		//step 3 有效权重默认与权重相同，通讯异常时-1, 通讯成功+1，直到恢复到weight大小
		if w.effectiveWeight < w.weight {
			w.effectiveWeight++
		}
		//step 4 选择最大临时权重点节点
		if best == nil || w.currentWeight > best.currentWeight {
			best = w
		}
	}
	if best == nil {
		return ""
	}
	//step 5 变更临时权重为 临时权重-有效权重之和
	best.currentWeight -= total
	return best.addr
}
func (r *WeightRoundRobinBalance) Get(key string) (string, error) {
	return r.Next(), nil
}

节点有效权重：故障一次，权重减一 为了检测服务器故障准备的

加权轮询过程

一致性哈希负载

package consist_hash

import (
	"errors"
	"hash/crc32"
	"sort"
	"strconv"
	"sync"
)

type Hash func(data []byte) uint32

type UInt32Slice []uint32

func (s UInt32Slice) Len() int {
	return len(s)
}

func (s UInt32Slice) Less(i, j int) bool {
	return s[i] < s[j]
}

func (s UInt32Slice) Swap(i, j int) {
	s[i], s[j] = s[j], s[i]
}

type ConsistentHashBanlance struct {
	mux      sync.RWMutex
	hash     Hash
	replicas int               //复制因子
	keys     UInt32Slice       //已排序的节点hash切片
	hashMap  map[uint32]string //节点哈希和Key的map,键是hash值，值是节点key

	//观察主体
	//conf LoadBalanceConf
}

func NewConsistentHashBanlance(replicas int, fn Hash) *ConsistentHashBanlance {
	m := &ConsistentHashBanlance{
		replicas: replicas,
		hash:     fn,
		hashMap:  make(map[uint32]string),
	}
	if m.hash == nil {
		//最多32位,保证是一个2^32-1环
		m.hash = crc32.ChecksumIEEE
	}
	return m
}

// 验证是否为空
func (c *ConsistentHashBanlance) IsEmpty() bool {
	return len(c.keys) == 0
}

// Add 方法用来添加缓存节点，参数为节点key，比如使用IP
func (c *ConsistentHashBanlance) Add(params ...string) error {
	if len(params) == 0 {
		return errors.New("param len 1 at least")
	}
	addr := params[0]
	c.mux.Lock()
	defer c.mux.Unlock()
	// 结合复制因子计算所有虚拟节点的hash值，并存入m.keys中，同时在m.hashMap中保存哈希值和key的映射
	for i := 0; i < c.replicas; i++ {
		hash := c.hash([]byte(strconv.Itoa(i) + addr))
		c.keys = append(c.keys, hash)
		c.hashMap[hash] = addr
	}
	// 对所有虚拟节点的哈希值进行排序，方便之后进行二分查找
	sort.Sort(c.keys)
	return nil
}

// Get 方法根据给定的对象获取最靠近它的那个节点
func (c *ConsistentHashBanlance) Get(key string) (string, error) {
	if c.IsEmpty() {
		return "", errors.New("node is empty")
	}
	hash := c.hash([]byte(key))

	// 通过二分查找获取最优节点，第一个"服务器hash"值大于"数据hash"值的就是最优"服务器节点"
	idx := sort.Search(len(c.keys), func(i int) bool { return c.keys[i] >= hash })

	// 如果查找结果 大于 服务器节点哈希数组的最大索引，表示此时该对象哈希值位于最后一个节点之后，那么放入第一个节点中
	if idx == len(c.keys) {
		idx = 0
	}
	c.mux.RLock()
	defer c.mux.RUnlock()
	return c.hashMap[c.keys[idx]], nil
}

//func (c *ConsistentHashBanlance) SetConf(conf LoadBalanceConf) {
//	c.conf = conf
//}
//
//func (c *ConsistentHashBanlance) Update() {
//	if conf, ok := c.conf.(*LoadBalanceZkConf); ok {
//		fmt.Println("Update get conf:", conf.GetConf())
//		c.keys = nil
//		c.hashMap = nil
//		for _, ip := range conf.GetConf() {
//			c.Add(strings.Split(ip, ",")...)
//		}
//	}
//	if conf, ok := c.conf.(*LoadBalanceCheckConf); ok {
//		fmt.Println("Update get conf:", conf.GetConf())
//		c.keys = nil
//		c.hashMap = map[uint32]string{}
//		for _, ip := range conf.GetConf() {
//			c.Add(strings.Split(ip, ",")...)
//		}
//	}
//}

请求访问指定的IP

• 单调性
• 平衡性 可以引入虚拟结点 拷贝服务器结点
• 分散性
  
  

为反向代理添加负载均衡

使用工厂方法

// LoadBalanceFactory 负载均衡的工厂模式
func LoadBalanceFactory(lbType LbType) LoadBalance {
	switch lbType {
	case LbRandom:
		return &random.RandomBalance{}
	case LbRoundRobin:
		return &round.RoundRobinBalance{}
	case LbWeightRoundRobin:
		return &weight.WeightRoundRobinBalance{}
	case LbConsistentHash:
		return consist_hash.NewConsistentHashBanlance(10, nil)
	default:
		return &random.RandomBalance{}
	}
}

使用接口统一封装

type LoadBalance interface {
	Add(...string) error
	Get(string) (string, error)

	// Update 后期服务发现补充
	//Update()
}

package main

import (
	"bytes"
	"gateway-detail/load_balance/lb_factory"
	"io"
	"log"
	"net"
	"net/http"
	"net/http/httputil"
	"net/url"
	"strconv"
	"strings"
	"time"
)

var (
	addr      = "127.0.0.1:2224"
	transport = &http.Transport{
		DialContext: (&net.Dialer{
			Timeout:   30 * time.Second, //连接超时
			KeepAlive: 30 * time.Second, //长连接超时时间
		}).DialContext,
		MaxIdleConns:          100,              //最大空闲连接
		IdleConnTimeout:       90 * time.Second, //空闲超时时间
		TLSHandshakeTimeout:   10 * time.Second, //tls握手超时时间
		ExpectContinueTimeout: 1 * time.Second,  //100-continue状态码超时时间
	}
)

func NewMultipleHostsReverseProxy(lb lb_factory.LoadBalance) *httputil.ReverseProxy {
	// 请求协调者
	director := func(req *http.Request) {
		nextAddr, err := lb.Get(req.RemoteAddr)
		if err != nil {
			log.Println(err.Error())
			log.Fatal("get next addr fail")

		}
		target, err := url.Parse(nextAddr)
		if err != nil {
			log.Fatal(err)
		}
		//改造req
		targetQuery := target.RawQuery
		req.URL.Scheme = target.Scheme
		req.URL.Host = target.Host
		req.URL.Path = singleJoiningSlash(target.Path, req.URL.Path)
		if targetQuery == "" || req.URL.RawQuery == "" {
			req.URL.RawQuery = targetQuery + req.URL.RawQuery
		} else {
			req.URL.RawQuery = targetQuery + "&" + req.URL.RawQuery
		}
		if _, ok := req.Header["User-Agent"]; !ok {
			req.Header.Set("User-Agent", "user-agent")
		}
	}

	//更改内容
	modifyFunc := func(resp *http.Response) error {
		//请求以下命令：curl 'http://127.0.0.1:2002/error'
		if resp.StatusCode != 200 {
			//获取内容
		}
		//追加内容
		oldPayload, err := io.ReadAll(resp.Body)
		if err != nil {
			return err
		}
		newPayload := []byte("Hello :" + string(oldPayload))
		resp.Body = io.NopCloser(bytes.NewBuffer(newPayload))
		resp.ContentLength = int64(len(newPayload))
		resp.Header.Set("Content-Length", strconv.FormatInt(int64(len(newPayload)), 10))
		return nil
	}
	//错误回调 ：关闭real_server时测试，错误回调
	//范围：transport.RoundTrip发生的错误、以及ModifyResponse发生的错误
	errFunc := func(w http.ResponseWriter, r *http.Request, err error) {
		//todo 如果是权重的负载则调整临时权重
		http.Error(w, "ErrorHandler error:"+err.Error(), 500)
	}
	return &httputil.ReverseProxy{Director: director, Transport: transport, ModifyResponse: modifyFunc, ErrorHandler: errFunc}
}
func singleJoiningSlash(a, b string) string {
	aslash := strings.HasSuffix(a, "/")
	bslash := strings.HasPrefix(b, "/")
	switch {
	case aslash && bslash:
		return a + b[1:]
	case !aslash && !bslash:
		return a + "/" + b
	}
	return a + b
}

func main() {
	rb := lb_factory.LoadBalanceFactory(lb_factory.LbConsistentHash)
	if err := rb.Add("http://127.0.0.1:2003/base", "10"); err != nil {
		log.Println(err)
	}
	if err := rb.Add("http://127.0.0.1:2004/base", "50"); err != nil {
		log.Println(err)
	}
	proxy := NewMultipleHostsReverseProxy(rb)
	log.Println("Starting httpserver at " + addr)
	log.Fatal(http.ListenAndServe(addr, proxy))
}