mirror of https://github.com/k3s-io/k3s
105 lines
2.5 KiB
Go
105 lines
2.5 KiB
Go
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/*
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Copyright 2014 Google Inc. All rights reserved.
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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 util
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import (
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"sync"
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"time"
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)
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type RateLimiter interface {
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// CanAccept returns true if the rate is below the limit, false otherwise
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CanAccept() bool
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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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}
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type tickRateLimiter struct {
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lock sync.Mutex
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tokens chan bool
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ticker <-chan time.Time
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stop chan bool
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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, the rate limiter spawns a go routine
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// which refills the bucket with one token at a rate of 'qps'. The maximum number of tokens in
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// the bucket is capped at 'burst'.
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// When done with the limiter, Stop() must be called to halt the associated goroutine.
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func NewTokenBucketRateLimiter(qps float32, burst int) RateLimiter {
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ticker := time.Tick(time.Duration(float32(time.Second) / qps))
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rate := newTokenBucketRateLimiterFromTicker(ticker, burst)
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go rate.run()
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return rate
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}
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func newTokenBucketRateLimiterFromTicker(ticker <-chan time.Time, burst int) *tickRateLimiter {
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if burst < 1 {
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panic("burst must be a positive integer")
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}
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rate := &tickRateLimiter{
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tokens: make(chan bool, burst),
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ticker: ticker,
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stop: make(chan bool),
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}
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for i := 0; i < burst; i++ {
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rate.tokens <- true
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}
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return rate
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}
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func (t *tickRateLimiter) CanAccept() bool {
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select {
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case <-t.tokens:
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return true
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default:
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return false
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}
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}
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func (t *tickRateLimiter) Stop() {
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close(t.stop)
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}
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func (r *tickRateLimiter) run() {
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for {
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if !r.step() {
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break
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}
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}
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}
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func (r *tickRateLimiter) step() bool {
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select {
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case <-r.ticker:
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r.increment()
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return true
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case <-r.stop:
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return false
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}
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}
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func (t *tickRateLimiter) increment() {
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// non-blocking send
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select {
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case t.tokens <- true:
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default:
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}
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}
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