Merge pull request #38320 from liggitt/golang-ratelimit

Automatic merge from submit-queue (batch tested with PRs 59158, 38320, 59059, 55516, 59357). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Switch from juju/ratelimit to golang.org/x/time/rate

Replaces juju/ratelimit with golang.org/x/time/rate
xref https://github.com/kubernetes/steering/issues/21

Requires removing the Saturation() method on the rate limiter. In the process of attempting to contribute it to the `golang.org/x/time/rate` implementation, it became clear that what it was calculating was not very useful when combined with periodic polling. See discussion in https://go-review.googlesource.com/c/time/+/29958#message-4caffc11669cadd90e2da4c05122cfec50ea6a22

```release-note
NONE
```

Kubernetes-commit: 0656d030a7d131ca8088a9f0ecd12596eb90d2fd

vendor/k8s.io/client-go/util/flowcontrol/throttle.go

@@ -18,8 +18,9 @@ package flowcontrol
 
 import (
 	"sync"
+	"time"
 
-	"github.com/juju/ratelimit"
+	"golang.org/x/time/rate"
 )
 
 type RateLimiter interface {
@@ -30,17 +31,13 @@ type RateLimiter interface {
 	Accept()
 	// Stop stops the rate limiter, subsequent calls to CanAccept will return false
 	Stop()
-	// Saturation returns a percentage number which describes how saturated
-	// this rate limiter is.
-	// Usually we use token bucket rate limiter. In that case,
-	// 1.0 means no tokens are available; 0.0 means we have a full bucket of tokens to use.
-	Saturation() float64
 	// QPS returns QPS of this rate limiter
 	QPS() float32
 }
 
 type tokenBucketRateLimiter struct {
-	limiter *ratelimit.Bucket
+	limiter *rate.Limiter
+	clock   Clock
 	qps     float32
 }
 
@@ -50,42 +47,48 @@ type tokenBucketRateLimiter struct {
 // The bucket is initially filled with 'burst' tokens, and refills at a rate of 'qps'.
 // The maximum number of tokens in the bucket is capped at 'burst'.
 func NewTokenBucketRateLimiter(qps float32, burst int) RateLimiter {
-	limiter := ratelimit.NewBucketWithRate(float64(qps), int64(burst))
-	return newTokenBucketRateLimiter(limiter, qps)
+	limiter := rate.NewLimiter(rate.Limit(qps), burst)
+	return newTokenBucketRateLimiter(limiter, realClock{}, qps)
 }
 
 // An injectable, mockable clock interface.
 type Clock interface {
-	ratelimit.Clock
+	Now() time.Time
+	Sleep(time.Duration)
+}
+
+type realClock struct{}
+
+func (realClock) Now() time.Time {
+	return time.Now()
+}
+func (realClock) Sleep(d time.Duration) {
+	time.Sleep(d)
 }
 
 // NewTokenBucketRateLimiterWithClock is identical to NewTokenBucketRateLimiter
 // but allows an injectable clock, for testing.
-func NewTokenBucketRateLimiterWithClock(qps float32, burst int, clock Clock) RateLimiter {
-	limiter := ratelimit.NewBucketWithRateAndClock(float64(qps), int64(burst), clock)
-	return newTokenBucketRateLimiter(limiter, qps)
+func NewTokenBucketRateLimiterWithClock(qps float32, burst int, c Clock) RateLimiter {
+	limiter := rate.NewLimiter(rate.Limit(qps), burst)
+	return newTokenBucketRateLimiter(limiter, c, qps)
 }
 
-func newTokenBucketRateLimiter(limiter *ratelimit.Bucket, qps float32) RateLimiter {
+func newTokenBucketRateLimiter(limiter *rate.Limiter, c Clock, qps float32) RateLimiter {
 	return &tokenBucketRateLimiter{
 		limiter: limiter,
+		clock:   c,
 		qps:     qps,
 	}
 }
 
 func (t *tokenBucketRateLimiter) TryAccept() bool {
-	return t.limiter.TakeAvailable(1) == 1
-}
-
-func (t *tokenBucketRateLimiter) Saturation() float64 {
-	capacity := t.limiter.Capacity()
-	avail := t.limiter.Available()
-	return float64(capacity-avail) / float64(capacity)
+	return t.limiter.AllowN(t.clock.Now(), 1)
 }
 
 // Accept will block until a token becomes available
 func (t *tokenBucketRateLimiter) Accept() {
-	t.limiter.Wait(1)
+	now := t.clock.Now()
+	t.clock.Sleep(t.limiter.ReserveN(now, 1).DelayFrom(now))
 }
 
 func (t *tokenBucketRateLimiter) Stop() {
@@ -105,10 +108,6 @@ func (t *fakeAlwaysRateLimiter) TryAccept() bool {
 	return true
 }
 
-func (t *fakeAlwaysRateLimiter) Saturation() float64 {
-	return 0
-}
-
 func (t *fakeAlwaysRateLimiter) Stop() {}
 
 func (t *fakeAlwaysRateLimiter) Accept() {}
@@ -131,10 +130,6 @@ func (t *fakeNeverRateLimiter) TryAccept() bool {
 	return false
 }
 
-func (t *fakeNeverRateLimiter) Saturation() float64 {
-	return 1
-}
-
 func (t *fakeNeverRateLimiter) Stop() {
 	t.wg.Done()
 }