init

internal/mesh/rendezvous.go

@@ -0,0 +1,49 @@
+package mesh
+
+import (
+	"crypto/sha256"
+	"encoding/binary"
+	"sort"
+	"sync"
+)
+
+type Rendezvous struct {
+	mu    sync.RWMutex
+	nodes []string // node IDs
+}
+
+func NewRendezvous() *Rendezvous { return &Rendezvous{} }
+
+func (r *Rendezvous) Set(ids []string) {
+	r.mu.Lock()
+	r.nodes = append([]string(nil), ids...)
+	r.mu.Unlock()
+}
+
+func (r *Rendezvous) Owners(key string, k int) []string {
+	r.mu.RLock()
+	ids := append([]string(nil), r.nodes...)
+	r.mu.RUnlock()
+	if len(ids) == 0 {
+		return nil
+	}
+	type pair struct {
+		id string
+		w  uint64
+	}
+	ws := make([]pair, 0, len(ids))
+	for _, id := range ids {
+		h := sha256.Sum256([]byte(id + "|" + key))
+		w := binary.LittleEndian.Uint64(h[:8])
+		ws = append(ws, pair{id: id, w: w})
+	}
+	sort.Slice(ws, func(i, j int) bool { return ws[i].w > ws[j].w })
+	if k > len(ws) {
+		k = len(ws)
+	}
+	out := make([]string, 0, k)
+	for i := 0; i < k; i++ {
+		out = append(out, ws[i].id)
+	}
+	return out
+}