Accountant: Inventar, where, Checkmk, Abrechnung

pkg/ratelimit/ratelimit.go

@@ -0,0 +1,61 @@
+package server
+
+import (
+	"sync"
+	"time"
+)
+
+// rateLimiter begrenzt Versuche je Schlüssel (Client-IP) auf limit pro
+// window (gleitendes Fenster). limit < 0 = unbegrenzt.
+type rateLimiter struct {
+	limit  int
+	window time.Duration
+	now    func() time.Time
+
+	mu        sync.Mutex
+	hits      map[string][]time.Time
+	lastPurge time.Time
+}
+
+// allow verbucht einen Versuch; bei Ablehnung liefert es die Wartezeit.
+func (l *rateLimiter) allow(key string) (bool, time.Duration) {
+	if l.limit < 0 {
+		return true, 0
+	}
+	now := time.Now()
+	if l.now != nil {
+		now = l.now()
+	}
+	cutoff := now.Add(-l.window)
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	if l.hits == nil {
+		l.hits = map[string][]time.Time{}
+	}
+	if now.Sub(l.lastPurge) >= l.window { // vergessen, was nicht mehr zählt
+		for k, ts := range l.hits {
+			if !ts[len(ts)-1].After(cutoff) {
+				delete(l.hits, k)
+			}
+		}
+		l.lastPurge = now
+	}
+	ts := l.hits[key]
+	i := 0
+	for i < len(ts) && !ts[i].After(cutoff) {
+		i++
+	}
+	ts = ts[i:]
+	if len(ts) >= l.limit {
+		l.hits[key] = ts
+		return false, ts[0].Add(l.window).Sub(now)
+	}
+	l.hits[key] = append(ts, now)
+	return true, 0
+}
+
+func (l *rateLimiter) size() int {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	return len(l.hits)
+}