From f265d5c5eebbd76048228573ba63d2ac34b554fa Mon Sep 17 00:00:00 2001
From: Jordan Liggitt <jliggitt@redhat.com>
Date: Tue, 30 Jun 2015 09:59:37 -0400
Subject: [PATCH] Switch token bucket rate limiter to github.com/juju/ratelimit

---
 pkg/util/throttle.go      | 73 +++++----------------------------------
 pkg/util/throttle_test.go | 21 +++--------
 2 files changed, 13 insertions(+), 81 deletions(-)

diff --git a/pkg/util/throttle.go b/pkg/util/throttle.go
index e10f372746..43fdc0a946 100644
--- a/pkg/util/throttle.go
+++ b/pkg/util/throttle.go
@@ -16,10 +16,7 @@ limitations under the License.
 
 package util
 
-import (
-	"sync"
-	"time"
-)
+import "github.com/juju/ratelimit"
 
 type RateLimiter interface {
 	// CanAccept returns true if the rate is below the limit, false otherwise
@@ -31,24 +28,17 @@ type RateLimiter interface {
 }
 
 type tickRateLimiter struct {
-	lock   sync.Mutex
-	tokens chan bool
-	ticker <-chan time.Time
-	stop   chan bool
+	limiter *ratelimit.Bucket
 }
 
 // NewTokenBucketRateLimiter creates a rate limiter which implements a token bucket approach.
 // The rate limiter allows bursts of up to 'burst' to exceed the QPS, while still maintaining a
 // smoothed qps rate of 'qps'.
-// The bucket is initially filled with 'burst' tokens, the rate limiter spawns a go routine
-// which refills the bucket with one token at a rate of 'qps'.  The maximum number of tokens in
-// the bucket is capped at 'burst'.
-// When done with the limiter, Stop() must be called to halt the associated goroutine.
+// 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 {
-	ticker := time.Tick(time.Duration(float32(time.Second) / qps))
-	rate := newTokenBucketRateLimiterFromTicker(ticker, burst)
-	go rate.run()
-	return rate
+	limiter := ratelimit.NewBucketWithRate(float64(qps), int64(burst))
+	return &tickRateLimiter{limiter}
 }
 
 type fakeRateLimiter struct{}
@@ -57,63 +47,16 @@ func NewFakeRateLimiter() RateLimiter {
 	return &fakeRateLimiter{}
 }
 
-func newTokenBucketRateLimiterFromTicker(ticker <-chan time.Time, burst int) *tickRateLimiter {
-	if burst < 1 {
-		panic("burst must be a positive integer")
-	}
-	rate := &tickRateLimiter{
-		tokens: make(chan bool, burst),
-		ticker: ticker,
-		stop:   make(chan bool),
-	}
-	for i := 0; i < burst; i++ {
-		rate.tokens <- true
-	}
-	return rate
-}
-
 func (t *tickRateLimiter) CanAccept() bool {
-	select {
-	case <-t.tokens:
-		return true
-	default:
-		return false
-	}
+	return t.limiter.TakeAvailable(1) == 1
 }
 
 // Accept will block until a token becomes available
 func (t *tickRateLimiter) Accept() {
-	<-t.tokens
+	t.limiter.Wait(1)
 }
 
 func (t *tickRateLimiter) Stop() {
-	close(t.stop)
-}
-
-func (r *tickRateLimiter) run() {
-	for {
-		if !r.step() {
-			break
-		}
-	}
-}
-
-func (r *tickRateLimiter) step() bool {
-	select {
-	case <-r.ticker:
-		r.increment()
-		return true
-	case <-r.stop:
-		return false
-	}
-}
-
-func (t *tickRateLimiter) increment() {
-	// non-blocking send
-	select {
-	case t.tokens <- true:
-	default:
-	}
 }
 
 func (t *fakeRateLimiter) CanAccept() bool {
diff --git a/pkg/util/throttle_test.go b/pkg/util/throttle_test.go
index b8edd21653..b4b145b79d 100644
--- a/pkg/util/throttle_test.go
+++ b/pkg/util/throttle_test.go
@@ -22,8 +22,7 @@ import (
 )
 
 func TestBasicThrottle(t *testing.T) {
-	ticker := make(chan time.Time, 1)
-	r := newTokenBucketRateLimiterFromTicker(ticker, 3)
+	r := NewTokenBucketRateLimiter(1, 3)
 	for i := 0; i < 3; i++ {
 		if !r.CanAccept() {
 			t.Error("unexpected false accept")
@@ -35,32 +34,22 @@ func TestBasicThrottle(t *testing.T) {
 }
 
 func TestIncrementThrottle(t *testing.T) {
-	ticker := make(chan time.Time, 1)
-	r := newTokenBucketRateLimiterFromTicker(ticker, 1)
+	r := NewTokenBucketRateLimiter(1, 1)
 	if !r.CanAccept() {
 		t.Error("unexpected false accept")
 	}
 	if r.CanAccept() {
 		t.Error("unexpected true accept")
 	}
-	ticker <- time.Now()
-	r.step()
+
+	// Allow to refill
+	time.Sleep(2 * time.Second)
 
 	if !r.CanAccept() {
 		t.Error("unexpected false accept")
 	}
 }
 
-func TestOverBurst(t *testing.T) {
-	ticker := make(chan time.Time, 1)
-	r := newTokenBucketRateLimiterFromTicker(ticker, 3)
-
-	for i := 0; i < 4; i++ {
-		ticker <- time.Now()
-		r.step()
-	}
-}
-
 func TestThrottle(t *testing.T) {
 	r := NewTokenBucketRateLimiter(10, 5)