k8s.io/client-go@v0.22.2/util/flowcontrol/throttle.go (about)

     1  /*
     2  Copyright 2014 The Kubernetes Authors.
     3  
     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
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    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.
    15  */
    16  
    17  package flowcontrol
    18  
    19  import (
    20  	"context"
    21  	"errors"
    22  	"sync"
    23  	"time"
    24  
    25  	"golang.org/x/time/rate"
    26  )
    27  
    28  type RateLimiter interface {
    29  	// TryAccept returns true if a token is taken immediately. Otherwise,
    30  	// it returns false.
    31  	TryAccept() bool
    32  	// Accept returns once a token becomes available.
    33  	Accept()
    34  	// Stop stops the rate limiter, subsequent calls to CanAccept will return false
    35  	Stop()
    36  	// QPS returns QPS of this rate limiter
    37  	QPS() float32
    38  	// Wait returns nil if a token is taken before the Context is done.
    39  	Wait(ctx context.Context) error
    40  }
    41  
    42  type tokenBucketRateLimiter struct {
    43  	limiter *rate.Limiter
    44  	clock   Clock
    45  	qps     float32
    46  }
    47  
    48  // NewTokenBucketRateLimiter creates a rate limiter which implements a token bucket approach.
    49  // The rate limiter allows bursts of up to 'burst' to exceed the QPS, while still maintaining a
    50  // smoothed qps rate of 'qps'.
    51  // The bucket is initially filled with 'burst' tokens, and refills at a rate of 'qps'.
    52  // The maximum number of tokens in the bucket is capped at 'burst'.
    53  func NewTokenBucketRateLimiter(qps float32, burst int) RateLimiter {
    54  	limiter := rate.NewLimiter(rate.Limit(qps), burst)
    55  	return newTokenBucketRateLimiter(limiter, realClock{}, qps)
    56  }
    57  
    58  // An injectable, mockable clock interface.
    59  type Clock interface {
    60  	Now() time.Time
    61  	Sleep(time.Duration)
    62  }
    63  
    64  type realClock struct{}
    65  
    66  func (realClock) Now() time.Time {
    67  	return time.Now()
    68  }
    69  func (realClock) Sleep(d time.Duration) {
    70  	time.Sleep(d)
    71  }
    72  
    73  // NewTokenBucketRateLimiterWithClock is identical to NewTokenBucketRateLimiter
    74  // but allows an injectable clock, for testing.
    75  func NewTokenBucketRateLimiterWithClock(qps float32, burst int, c Clock) RateLimiter {
    76  	limiter := rate.NewLimiter(rate.Limit(qps), burst)
    77  	return newTokenBucketRateLimiter(limiter, c, qps)
    78  }
    79  
    80  func newTokenBucketRateLimiter(limiter *rate.Limiter, c Clock, qps float32) RateLimiter {
    81  	return &tokenBucketRateLimiter{
    82  		limiter: limiter,
    83  		clock:   c,
    84  		qps:     qps,
    85  	}
    86  }
    87  
    88  func (t *tokenBucketRateLimiter) TryAccept() bool {
    89  	return t.limiter.AllowN(t.clock.Now(), 1)
    90  }
    91  
    92  // Accept will block until a token becomes available
    93  func (t *tokenBucketRateLimiter) Accept() {
    94  	now := t.clock.Now()
    95  	t.clock.Sleep(t.limiter.ReserveN(now, 1).DelayFrom(now))
    96  }
    97  
    98  func (t *tokenBucketRateLimiter) Stop() {
    99  }
   100  
   101  func (t *tokenBucketRateLimiter) QPS() float32 {
   102  	return t.qps
   103  }
   104  
   105  func (t *tokenBucketRateLimiter) Wait(ctx context.Context) error {
   106  	return t.limiter.Wait(ctx)
   107  }
   108  
   109  type fakeAlwaysRateLimiter struct{}
   110  
   111  func NewFakeAlwaysRateLimiter() RateLimiter {
   112  	return &fakeAlwaysRateLimiter{}
   113  }
   114  
   115  func (t *fakeAlwaysRateLimiter) TryAccept() bool {
   116  	return true
   117  }
   118  
   119  func (t *fakeAlwaysRateLimiter) Stop() {}
   120  
   121  func (t *fakeAlwaysRateLimiter) Accept() {}
   122  
   123  func (t *fakeAlwaysRateLimiter) QPS() float32 {
   124  	return 1
   125  }
   126  
   127  func (t *fakeAlwaysRateLimiter) Wait(ctx context.Context) error {
   128  	return nil
   129  }
   130  
   131  type fakeNeverRateLimiter struct {
   132  	wg sync.WaitGroup
   133  }
   134  
   135  func NewFakeNeverRateLimiter() RateLimiter {
   136  	rl := fakeNeverRateLimiter{}
   137  	rl.wg.Add(1)
   138  	return &rl
   139  }
   140  
   141  func (t *fakeNeverRateLimiter) TryAccept() bool {
   142  	return false
   143  }
   144  
   145  func (t *fakeNeverRateLimiter) Stop() {
   146  	t.wg.Done()
   147  }
   148  
   149  func (t *fakeNeverRateLimiter) Accept() {
   150  	t.wg.Wait()
   151  }
   152  
   153  func (t *fakeNeverRateLimiter) QPS() float32 {
   154  	return 1
   155  }
   156  
   157  func (t *fakeNeverRateLimiter) Wait(ctx context.Context) error {
   158  	return errors.New("can not be accept")
   159  }