// SwapLimiter safely swaps current limiter for this queue with the passed one if capacities or qps's differ.
func (q *RateLimitedTimedQueue) SwapLimiter(newQPS float32) {
	q.limiterLock.Lock()
	defer q.limiterLock.Unlock()
	if q.limiter.QPS() == newQPS {
		return
	}
	var newLimiter flowcontrol.RateLimiter
	if newQPS <= 0 {
		newLimiter = flowcontrol.NewFakeNeverRateLimiter()
	} else {
		newLimiter = flowcontrol.NewTokenBucketRateLimiter(newQPS, evictionRateLimiterBurst)
	}
	// If we're currently waiting on limiter, we drain the new one - this is a good approach when Burst value is 1
	// TODO: figure out if we need to support higher Burst values and decide on the drain logic, should we keep:
	// - saturation (percentage of used tokens)
	// - number of used tokens
	// - number of available tokens
	// - something else
	for q.limiter.Saturation() > newLimiter.Saturation() {
		// Check if we're not using fake limiter
		previousSaturation := newLimiter.Saturation()
		newLimiter.TryAccept()
		// It's a fake limiter
		if newLimiter.Saturation() == previousSaturation {
			break
		}
	}
	q.limiter.Stop()
	q.limiter = newLimiter
}
func TestSwapLimiter(t *testing.T) {
	evictor := NewRateLimitedTimedQueue(flowcontrol.NewFakeAlwaysRateLimiter())
	fakeAlways := flowcontrol.NewFakeAlwaysRateLimiter()
	qps := evictor.limiter.QPS()
	if qps != fakeAlways.QPS() {
		t.Fatalf("QPS does not match create one: %v instead of %v", qps, fakeAlways.QPS())
	}

	evictor.SwapLimiter(0)
	qps = evictor.limiter.QPS()
	fakeNever := flowcontrol.NewFakeNeverRateLimiter()
	if qps != fakeNever.QPS() {
		t.Fatalf("QPS does not match create one: %v instead of %v", qps, fakeNever.QPS())
	}

	createdQPS := float32(5.5)
	evictor.SwapLimiter(createdQPS)
	qps = evictor.limiter.QPS()
	if qps != createdQPS {
		t.Fatalf("QPS does not match create one: %v instead of %v", qps, createdQPS)
	}
}