118 lines
2.2 KiB
Go
118 lines
2.2 KiB
Go
package hashring
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import (
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"crypto/sha1"
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// "hash"
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"math"
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"sort"
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"strconv"
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)
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const (
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DefaultVirualSpots = 40
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)
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type node struct {
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nodeKey string
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spotValue uint32
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}
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type nodesArray []node
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func (p nodesArray) Len() int { return len(p) }
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func (p nodesArray) Less(i, j int) bool { return p[i].spotValue < p[j].spotValue }
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func (p nodesArray) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
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func (p nodesArray) Sort() { sort.Sort(p) }
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type HashRing struct {
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virualSpots int
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nodes nodesArray
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weights map[string]int
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}
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func NewHashRing(spots int) *HashRing {
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if spots == 0 {
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spots = DefaultVirualSpots
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}
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h := &HashRing{
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virualSpots: spots,
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weights: make(map[string]int),
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}
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return h
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}
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func (h *HashRing) AddNodes(nodeWeight map[string]int) {
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for nodeKey, w := range nodeWeight {
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h.weights[nodeKey] = w
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}
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h.generate()
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}
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func (h *HashRing) AddNode(nodeKey string, weight int) {
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h.weights[nodeKey] = weight
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h.generate()
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}
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func (h *HashRing) RemoveNode(nodeKey string) {
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delete(h.weights, nodeKey)
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h.generate()
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}
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func (h *HashRing) UpdateNode(nodeKey string, weight int) {
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h.weights[nodeKey] = weight
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h.generate()
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}
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func (h *HashRing) generate() {
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var totalW int
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for _, w := range h.weights {
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totalW += w
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}
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totalVirtualSpots := h.virualSpots * len(h.weights)
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h.nodes = nodesArray{}
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for nodeKey, w := range h.weights {
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spots := int(math.Floor(float64(w) / float64(totalW) * float64(totalVirtualSpots)))
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for i := 1; i <= spots; i++ {
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hash := sha1.New()
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hash.Write([]byte(nodeKey + ":" + strconv.Itoa(i)))
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hashBytes := hash.Sum(nil)
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n := node{
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nodeKey: nodeKey,
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spotValue: genValue(hashBytes[6:10]),
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}
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h.nodes = append(h.nodes, n)
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hash.Reset()
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}
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}
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h.nodes.Sort()
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}
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func genValue(bs []byte) uint32 {
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if len(bs) < 4 {
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return 0
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}
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v := (uint32(bs[3]) << 24) | (uint32(bs[2]) << 16) | (uint32(bs[1]) << 8) | (uint32(bs[0]))
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return v
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}
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func (h *HashRing) GetNode(s string) string {
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if len(h.nodes) == 0 {
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return ""
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}
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hash := sha1.New()
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hash.Write([]byte(s))
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hashBytes := hash.Sum(nil)
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v := genValue(hashBytes[6:10])
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i := sort.Search(len(h.nodes), func(i int) bool { return h.nodes[i].spotValue >= v })
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if i == len(h.nodes) {
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i = 0
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}
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return h.nodes[i].nodeKey
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}
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