2 Copyright 2014 The Kubernetes Authors.
4 Licensed under the Apache License, Version 2.0 (the "License");
5 you may not use this file except in compliance with the License.
6 You may obtain a copy of the License at
8 http://www.apache.org/licenses/LICENSE-2.0
10 Unless required by applicable law or agreed to in writing, software
11 distributed under the License is distributed on an "AS IS" BASIS,
12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 See the License for the specific language governing permissions and
14 limitations under the License.
23 "golang.org/x/time/rate"
26 type RateLimiter interface {
27 // TryAccept returns true if a token is taken immediately. Otherwise,
30 // Accept returns once a token becomes available.
32 // Stop stops the rate limiter, subsequent calls to CanAccept will return false
34 // QPS returns QPS of this rate limiter
38 type tokenBucketRateLimiter struct {
44 // NewTokenBucketRateLimiter creates a rate limiter which implements a token bucket approach.
45 // The rate limiter allows bursts of up to 'burst' to exceed the QPS, while still maintaining a
46 // smoothed qps rate of 'qps'.
47 // The bucket is initially filled with 'burst' tokens, and refills at a rate of 'qps'.
48 // The maximum number of tokens in the bucket is capped at 'burst'.
49 func NewTokenBucketRateLimiter(qps float32, burst int) RateLimiter {
50 limiter := rate.NewLimiter(rate.Limit(qps), burst)
51 return newTokenBucketRateLimiter(limiter, realClock{}, qps)
54 // An injectable, mockable clock interface.
55 type Clock interface {
60 type realClock struct{}
62 func (realClock) Now() time.Time {
65 func (realClock) Sleep(d time.Duration) {
69 // NewTokenBucketRateLimiterWithClock is identical to NewTokenBucketRateLimiter
70 // but allows an injectable clock, for testing.
71 func NewTokenBucketRateLimiterWithClock(qps float32, burst int, c Clock) RateLimiter {
72 limiter := rate.NewLimiter(rate.Limit(qps), burst)
73 return newTokenBucketRateLimiter(limiter, c, qps)
76 func newTokenBucketRateLimiter(limiter *rate.Limiter, c Clock, qps float32) RateLimiter {
77 return &tokenBucketRateLimiter{
84 func (t *tokenBucketRateLimiter) TryAccept() bool {
85 return t.limiter.AllowN(t.clock.Now(), 1)
88 // Accept will block until a token becomes available
89 func (t *tokenBucketRateLimiter) Accept() {
91 t.clock.Sleep(t.limiter.ReserveN(now, 1).DelayFrom(now))
94 func (t *tokenBucketRateLimiter) Stop() {
97 func (t *tokenBucketRateLimiter) QPS() float32 {
101 type fakeAlwaysRateLimiter struct{}
103 func NewFakeAlwaysRateLimiter() RateLimiter {
104 return &fakeAlwaysRateLimiter{}
107 func (t *fakeAlwaysRateLimiter) TryAccept() bool {
111 func (t *fakeAlwaysRateLimiter) Stop() {}
113 func (t *fakeAlwaysRateLimiter) Accept() {}
115 func (t *fakeAlwaysRateLimiter) QPS() float32 {
119 type fakeNeverRateLimiter struct {
123 func NewFakeNeverRateLimiter() RateLimiter {
124 rl := fakeNeverRateLimiter{}
129 func (t *fakeNeverRateLimiter) TryAccept() bool {
133 func (t *fakeNeverRateLimiter) Stop() {
137 func (t *fakeNeverRateLimiter) Accept() {
141 func (t *fakeNeverRateLimiter) QPS() float32 {