隨機負載
隨機挑選目標服務器
package load_balance
import (
"errors"
"math/rand"
)
//隨機負載均衡
type RandomBalance struct {
curIndex int
rss []string
}
func (r *RandomBalance) Add(params ...string) error {
if len(params) == 0 {
return errors.New("params len 1 at least")
}
addr := params[0]
r.rss = append(r.rss, addr)
return nil
}
func (r *RandomBalance) Next() string {
if len(r.rss) == 0 {
return ""
}
r.curIndex = rand.Intn(len(r.rss))
return r.rss[r.curIndex]
}
func (r *RandomBalance) Get(string) (string, error) {
return r.Next(), nil
}
輪詢負載
服務器依次輪詢
package load_balance
import "errors"
//輪詢負載均衡
type RoundRobinBalance struct {
curIndex int
rss []string
}
func (r *RoundRobinBalance) Add(params ...string) error {
if len(params) == 0 {
return errors.New("params 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(string) (string, error) {
return r.Next(), nil
}
加權輪詢負載
給目標設置訪問權重，按照權重輪詢
package load_balance
import (
"errors"
"strconv"
)
type WeightRoundRobinBalance struct {
curIndex int
rss []*WeightNode
rsw []int
}
type WeightNode struct {
addr string
Weight int //初始化時對節點約定的權重
currentWeight int //節點臨時權重，每輪都會變化
effectiveWeight int //有效權重, 默認與weight相同 , totalWeight = sum(effectiveWeight) //出現故障就-1
}
//1, currentWeight = currentWeight + effectiveWeight
//2, 選中最大的currentWeight節點為選中節點
//3, currentWeight = currentWeight - totalWeight
func (r *WeightRoundRobinBalance) Add(params ...string) error {
if len(params) != 2 {
return errors.New("params 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 {
var best *WeightNode
total := 0
for i := 0; i len(r.rss); i++ {
w := r.rss[i]
//1 計算所有有效權重
total += w.effectiveWeight
//2 修改當前節點臨時權重
w.currentWeight += w.effectiveWeight
//3 有效權重默認與權重相同，通訊異常時-1, 通訊成功+1，直到恢復到weight大小
if w.effectiveWeight w.Weight {
w.effectiveWeight++
}
//4 選中最大臨時權重節點
if best == nil || w.currentWeight > best.currentWeight {
best = w
}
}
if best == nil {
return ""
}
//5 變更臨時權重為 臨時權重-有效權重之和
best.currentWeight -= total
return best.addr
}
func (r *WeightRoundRobinBalance) Get(string) (string, error) {
return r.Next(), nil
}
func (r *WeightRoundRobinBalance) Update() {
}
一致性hash
請求固定的URL訪問指定的IP
package load_balance
import (
"errors"
"hash/crc32"
"sort"
"strconv"
"sync"
)
//1 單調性（唯一） 2平衡性 (數據 目標元素均衡) 3分散性(散列)
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 ConsistentHashBalance struct {
mux sync.RWMutex
hash Hash
replicas int //復制因子
keys UInt32Slice //已排序的節點hash切片
hashMap map[uint32]string //節點哈希和key的map, 鍵是hash值，值是節點key
}
func NewConsistentHashBalance(replicas int, fn Hash) *ConsistentHashBalance {
m := ConsistentHashBalance{
replicas: replicas,
hash: fn,
hashMap: make(map[uint32]string),
}
if m.hash == nil {
//最多32位，保證是一個2^32-1環
m.hash = crc32.ChecksumIEEE
}
return m
}
func (c *ConsistentHashBalance) IsEmpty() bool {
return len(c.keys) == 0
}
// Add 方法用來添加緩存節點，參數為節點key，比如使用IP
func (c *ConsistentHashBalance) 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()
// 結合復制因子計算所有虛擬節點的hash值，并存入m.keys中，同時在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
}
// 對所有虛擬節點的哈希值進行排序，方便之后進行二分查找
sort.Sort(c.keys)
return nil
}
// Get 方法根據給定的對象獲取最靠近它的那個節點
func (c *ConsistentHashBalance) Get(key string) (string, error) {
if c.IsEmpty() {
return "", errors.New("node is empty")
}
hash := c.hash([]byte(key))
// 通過二分查找獲取最優節點，第一個"服務器hash"值大于"數據hash"值的就是最優"服務器節點"
idx := sort.Search(len(c.keys), func(i int) bool { return c.keys[i] >= hash })
// 如果查找結果 大于 服務器節點哈希數組的最大索引，表示此時該對象哈希值位于最后一個節點之后，那么放入第一個節點中
if idx == len(c.keys) {
idx = 0
}
c.mux.RLock()
defer c.mux.RUnlock()
return c.hashMap[c.keys[idx]], nil
}
封裝
定義LoadBalance接口
package load_balance
type LoadBalance interface {
Add(...string) error
Get(string)(string, error)
}
工廠方法
package load_balance
type LbType int
const (
LbRandom LbType = iota
LbRoundRobin
LbWeightRoundRobin
LbConsistentHash
)
func LoadBalanceFactory(lbType LbType) LoadBalance {
switch lbType {
case LbRandom:
return RandomBalance{}
case LbConsistentHash:
return NewConsistentHashBalance(10, nil)
case LbRoundRobin:
return RoundRobinBalance{}
case LbWeightRoundRobin:
return WeightRoundRobinBalance{}
default:
return RandomBalance{}
}
}
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