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117 lines
3.0 KiB
Go
117 lines
3.0 KiB
Go
/*
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Copyright 2014 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package flowcontrol
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import (
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"sync"
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"github.com/juju/ratelimit"
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)
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type RateLimiter interface {
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// TryAccept returns true if a token is taken immediately. Otherwise,
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// it returns false.
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TryAccept() bool
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// Accept returns once a token becomes available.
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Accept()
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// Stop stops the rate limiter, subsequent calls to CanAccept will return false
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Stop()
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// Saturation returns a percentage number which describes how saturated
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// this rate limiter is.
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// Usually we use token bucket rate limiter. In that case,
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// 1.0 means no tokens are available; 0.0 means we have a full bucket of tokens to use.
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Saturation() float64
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}
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type tokenBucketRateLimiter struct {
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limiter *ratelimit.Bucket
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}
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// NewTokenBucketRateLimiter creates a rate limiter which implements a token bucket approach.
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// The rate limiter allows bursts of up to 'burst' to exceed the QPS, while still maintaining a
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// smoothed qps rate of 'qps'.
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// The bucket is initially filled with 'burst' tokens, and refills at a rate of 'qps'.
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// The maximum number of tokens in the bucket is capped at 'burst'.
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func NewTokenBucketRateLimiter(qps float32, burst int) RateLimiter {
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limiter := ratelimit.NewBucketWithRate(float64(qps), int64(burst))
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return &tokenBucketRateLimiter{limiter}
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}
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func (t *tokenBucketRateLimiter) TryAccept() bool {
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return t.limiter.TakeAvailable(1) == 1
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}
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func (t *tokenBucketRateLimiter) Saturation() float64 {
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capacity := t.limiter.Capacity()
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avail := t.limiter.Available()
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return float64(capacity-avail) / float64(capacity)
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}
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// Accept will block until a token becomes available
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func (t *tokenBucketRateLimiter) Accept() {
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t.limiter.Wait(1)
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}
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func (t *tokenBucketRateLimiter) Stop() {
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}
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type fakeAlwaysRateLimiter struct{}
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func NewFakeAlwaysRateLimiter() RateLimiter {
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return &fakeAlwaysRateLimiter{}
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}
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func (t *fakeAlwaysRateLimiter) TryAccept() bool {
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return true
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}
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func (t *fakeAlwaysRateLimiter) Saturation() float64 {
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return 0
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}
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func (t *fakeAlwaysRateLimiter) Stop() {}
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func (t *fakeAlwaysRateLimiter) Accept() {}
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type fakeNeverRateLimiter struct {
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wg sync.WaitGroup
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}
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func NewFakeNeverRateLimiter() RateLimiter {
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wg := sync.WaitGroup{}
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wg.Add(1)
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return &fakeNeverRateLimiter{
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wg: wg,
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}
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}
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func (t *fakeNeverRateLimiter) TryAccept() bool {
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return false
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}
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func (t *fakeNeverRateLimiter) Saturation() float64 {
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return 1
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}
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func (t *fakeNeverRateLimiter) Stop() {
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t.wg.Done()
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}
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func (t *fakeNeverRateLimiter) Accept() {
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t.wg.Wait()
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}
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