snapshot of https://github.com/centrifugal/centrifugo.git (master, 2026-09-16; blobs > 131072B omitted)

internal/tools/interval_limiter.go

@@ -0,0 +1,35 @@
+package tools
+
+import (
+	"sync/atomic"
+	"time"
+)
+
+// IntervalLimiter permits an action at most once per configured interval. It is
+// safe for concurrent use and does no allocation or locking on the hot path -
+// just an atomic load (and a single CAS when the action is actually allowed),
+// so guarding a rare log line with it is effectively free when the interval has
+// not elapsed.
+type IntervalLimiter struct {
+	intervalNanos int64
+	lastNanos     atomic.Int64
+}
+
+// NewIntervalLimiter creates an IntervalLimiter that allows an action at most
+// once per interval.
+func NewIntervalLimiter(interval time.Duration) *IntervalLimiter {
+	return &IntervalLimiter{intervalNanos: int64(interval)}
+}
+
+// Allow reports whether the action may run now. Across all concurrent callers it
+// returns true at most once per interval. The first call always returns true.
+func (l *IntervalLimiter) Allow() bool {
+	now := time.Now().UnixNano()
+	last := l.lastNanos.Load()
+	if now-last < l.intervalNanos {
+		return false
+	}
+	// Only the caller that swaps in the new timestamp is allowed to proceed, so
+	// concurrent callers in the same window can't all log.
+	return l.lastNanos.CompareAndSwap(last, now)
+}