// 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)
}
}