72 lines
1.7 KiB
Go
72 lines
1.7 KiB
Go
package hash
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import (
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"fmt"
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"hash/crc32"
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"sort"
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"strconv"
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"strings"
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)
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// Consistency 一致性哈希生成
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//
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// https://blog.csdn.net/zhpCSDN921011/article/details/126845397
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type Consistency struct {
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Replicas int // 虚拟节点的数量
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keys []int // 所有虚拟节点的哈希值
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hashMap map[int]int // 虚拟节点的哈希值: 节点（虚拟节点映射到真实节点）
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}
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// AddNode 添加节点
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func (slf *Consistency) AddNode(keys ...int) {
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if slf.hashMap == nil {
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slf.hashMap = map[int]int{}
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}
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if slf.Replicas == 0 {
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slf.Replicas = 3
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}
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for _, key := range keys {
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for i := 0; i < slf.Replicas; i++ {
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// 计算虚拟节点哈希值
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hash := int(crc32.ChecksumIEEE([]byte(strconv.Itoa(i) + strconv.Itoa(key))))
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// 存储虚拟节点哈希值
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slf.keys = append(slf.keys, hash)
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// 存入map做映射
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slf.hashMap[hash] = key
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}
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}
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//排序哈希值，下面匹配的时候要二分搜索
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sort.Ints(slf.keys)
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}
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// PickNode 获取与 key 最接近的节点
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func (slf *Consistency) PickNode(key any) int {
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if len(slf.keys) == 0 {
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return 0
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}
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partitionKey := fmt.Sprintf("%#v", key)
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beg := strings.Index(partitionKey, "{")
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end := strings.Index(partitionKey, "}")
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if beg != -1 && !(end == -1 || end == beg+1) {
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partitionKey = partitionKey[beg+1 : end]
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}
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// 计算传入key的哈希值
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hash := int(crc32.ChecksumIEEE([]byte(partitionKey)))
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// sort.Search使用二分查找满足m.Keys[i]>=hash的最小哈希值
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idx := sort.Search(len(slf.keys), func(i int) bool { return slf.keys[i] >= hash })
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// 若key的hash值大于最后一个虚拟节点的hash值，则选择第一个虚拟节点
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if idx == len(slf.keys) {
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idx = 0
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}
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return slf.hashMap[slf.keys[idx]]
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}
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