✨ feat: Day4 一致性哈希

consistenthash/consistenthash.go

@@ -1,12 +1,18 @@
 package consistenthash
 
-import "hash/crc32"
+import (
+ "fmt"
+ "hash/crc32"
+ "sort"
+ "strconv"
+)
 
 type Hash func(data []byte) uint32
 
+// Map constains all hashed keys
 type Map struct {
  hash Hash
- replicas int //虚拟节点倍数
+ replicas int // 虚拟节点倍数
  keys []int // 哈希环
  hashMap map[int]string // 虚拟节点与真实节点的映射表，键是哈希值，值是真实节点的名称
 }
@@ -22,3 +28,32 @@ func New(replicas int, fn Hash) *Map {
  }
  return m
 }
+
+// Add adds some keys to the hash.
+// 传入真实节点名称
+func (m *Map) Add(keys ...string) {
+ for _, key := range keys {
+ for i := 0; i < m.replicas; i++ {
+ hash := int(m.hash([]byte(strconv.Itoa(i) + key)))
+ fmt.Printf("key: %v, i: %v, hash: %v\n", key, i, hash)
+ m.keys = append(m.keys, hash)
+ m.hashMap[hash] = key
+ }
+ }
+ sort.Ints(m.keys)
+}
+
+func(m *Map) Get(key string) string {
+ if len(m.keys) == 0 {
+ return ""
+ }
+
+ // 计算 key 的哈希值
+ hash := int(m.hash([]byte(key)))
+ // 顺时针找到第一个匹配的虚拟节点的下标 idx，从 m.keys 中获取对应的哈希值
+ idx := sort.Search(len(m.keys), func(i int) bool {
+ return m.keys[i] >= hash
+ })
+ // 得到真实节点
+ return m.hashMap[m.keys[idx%len(m.keys)]]
+}

consistenthash/consistenthash_test.go

@@ -0,0 +1,53 @@
+package consistenthash
+
+import (
+ "strconv"
+ "testing"
+)
+
+func TestHashing(t *testing.T) {
+ hash := New(3, func(key []byte) uint32 {
+ i, _ := strconv.Atoi(string(key))
+ return uint32(i)
+ })
+
+ // 哈希值: 2, 4, 6, 12, 14, 16, 22, 24, 26
+ hash.Add("6", "4", "2")
+ // fmt.Printf("%+v\n", hash)
+ // &{hash:0x77f740 replicas:3
+ // keys:[2 4 6 12 14 16 22 24 26]
+ // hashMap:map[2:2 4:4 6:6 12:2 14:4 16:6 22:2 24:4 26:6]}
+
+ testCases := map[string]string{
+ "2": "2",
+ "11": "2",
+ "23": "4",
+ "27": "2",
+ }
+
+ for k, v := range testCases {
+ if hash.Get(k) != v {
+ t.Errorf("Asking for %s, should have yielded %s", k, v)
+ }
+ }
+
+ hash.Add("8")
+ // fmt.Printf("%+v\n", hash)
+ // &{hash:0x5af740 replicas:3
+ // keys:[2 4 6 8 12 14 16 18 22 24 26 28]
+ // hashMap:map[2:2 4:4 6:6 8:8 12:2 14:4 16:6 18:8 22:2 24:4 26:6 28:8]}
+
+ testCases["27"] = "8"
+
+ for k, v := range testCases {
+ if hash.Get(k) != v {
+ t.Errorf("Asking for %s, should have yielded %s", k, v)
+ }
+ }
+
+ // hash.Add("9", "10", "11", "12", "233")
+ // fmt.Printf("%+v\n", hash)
+ // &{hash:0xf1f740 replicas:3
+ // keys:[2 4 6 8 9 10 11 12 12 14 16 18 19 22 24 26 28 29 110 111 112 210 211 212]
+ // hashMap:map[2:2 4:4 6:6 8:8 9:9 10:10 11:11 12:12 14:4 16:6 18:8 19:9 22:2 24:4 26:6 28:8 29:9 110:10 111:11 112:12 210:10 211:11 212:12]}
+}