Adding upstream version 1.34.4.

Signed-off-by: Daniel Baumann <daniel@debian.org>

plugins/common/ratelimiter/limiters.go

@@ -0,0 +1,66 @@
+package ratelimiter
+
+import (
+	"errors"
+	"math"
+	"time"
+)
+
+var (
+	ErrLimitExceeded = errors.New("not enough tokens")
+)
+
+type RateLimiter struct {
+	limit       int64
+	period      time.Duration
+	periodStart time.Time
+	remaining   int64
+}
+
+func (r *RateLimiter) Remaining(t time.Time) int64 {
+	if r.limit == 0 {
+		return math.MaxInt64
+	}
+
+	// Check for corner case
+	if !r.periodStart.Before(t) {
+		return 0
+	}
+
+	// We are in a new period, so the complete size is available
+	deltat := t.Sub(r.periodStart)
+	if deltat >= r.period {
+		return r.limit
+	}
+
+	return r.remaining
+}
+
+func (r *RateLimiter) Accept(t time.Time, used int64) {
+	if r.limit == 0 || r.periodStart.After(t) {
+		return
+	}
+
+	// Remember the first query and reset if we are in a new period
+	if r.periodStart.IsZero() {
+		r.periodStart = t
+		r.remaining = r.limit
+	} else if deltat := t.Sub(r.periodStart); deltat >= r.period {
+		r.periodStart = r.periodStart.Add(deltat.Truncate(r.period))
+		r.remaining = r.limit
+	}
+
+	// Update the state
+	r.remaining = max(r.remaining-used, 0)
+}
+
+func (r *RateLimiter) Undo(t time.Time, used int64) {
+	// Do nothing if we are not in the current period or unlimited because we
+	// already reset the limit on a new window.
+	if r.limit == 0 || r.periodStart.IsZero() || r.periodStart.After(t) || t.Sub(r.periodStart) >= r.period {
+		return
+	}
+
+	// Undo the state update
+	r.remaining = min(r.remaining+used, r.limit)
+}