109 lines
3.1 KiB
Go
109 lines
3.1 KiB
Go
package ratelimit
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import (
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"fmt"
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"strings"
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"time"
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"github.com/mailgun/timetools"
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"sort"
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)
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// TokenBucketSet represents a set of TokenBucket covering different time periods.
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type TokenBucketSet struct {
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buckets map[time.Duration]*tokenBucket
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maxPeriod time.Duration
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clock timetools.TimeProvider
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}
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// newTokenBucketSet creates a `TokenBucketSet` from the specified `rates`.
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func NewTokenBucketSet(rates *RateSet, clock timetools.TimeProvider) *TokenBucketSet {
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tbs := new(TokenBucketSet)
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tbs.clock = clock
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// In the majority of cases we will have only one bucket.
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tbs.buckets = make(map[time.Duration]*tokenBucket, len(rates.m))
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for _, rate := range rates.m {
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newBucket := newTokenBucket(rate, clock)
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tbs.buckets[rate.period] = newBucket
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tbs.maxPeriod = maxDuration(tbs.maxPeriod, rate.period)
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}
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return tbs
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}
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// Update brings the buckets in the set in accordance with the provided `rates`.
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func (tbs *TokenBucketSet) Update(rates *RateSet) {
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// Update existing buckets and delete those that have no corresponding spec.
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for _, bucket := range tbs.buckets {
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if rate, ok := rates.m[bucket.period]; ok {
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bucket.update(rate)
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} else {
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delete(tbs.buckets, bucket.period)
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}
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}
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// Add missing buckets.
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for _, rate := range rates.m {
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if _, ok := tbs.buckets[rate.period]; !ok {
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newBucket := newTokenBucket(rate, tbs.clock)
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tbs.buckets[rate.period] = newBucket
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}
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}
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// Identify the maximum period in the set
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tbs.maxPeriod = 0
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for _, bucket := range tbs.buckets {
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tbs.maxPeriod = maxDuration(tbs.maxPeriod, bucket.period)
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}
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}
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func (tbs *TokenBucketSet) Consume(tokens int64) (time.Duration, error) {
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var maxDelay time.Duration = UndefinedDelay
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var firstErr error = nil
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for _, tokenBucket := range tbs.buckets {
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// We keep calling `Consume` even after a error is returned for one of
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// buckets because that allows us to simplify the rollback procedure,
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// that is to just call `Rollback` for all buckets.
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delay, err := tokenBucket.consume(tokens)
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if firstErr == nil {
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if err != nil {
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firstErr = err
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} else {
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maxDelay = maxDuration(maxDelay, delay)
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}
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}
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}
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// If we could not make ALL buckets consume tokens for whatever reason,
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// then rollback consumption for all of them.
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if firstErr != nil || maxDelay > 0 {
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for _, tokenBucket := range tbs.buckets {
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tokenBucket.rollback()
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}
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}
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return maxDelay, firstErr
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}
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func (tbs *TokenBucketSet) GetMaxPeriod() time.Duration {
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return tbs.maxPeriod
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}
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// debugState returns string that reflects the current state of all buckets in
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// this set. It is intended to be used for debugging and testing only.
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func (tbs *TokenBucketSet) debugState() string {
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periods := sort.IntSlice(make([]int, 0, len(tbs.buckets)))
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for period := range tbs.buckets {
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periods = append(periods, int(period))
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}
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sort.Sort(periods)
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bucketRepr := make([]string, 0, len(tbs.buckets))
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for _, period := range periods {
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bucket := tbs.buckets[time.Duration(period)]
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bucketRepr = append(bucketRepr, fmt.Sprintf("{%v: %v}", bucket.period, bucket.availableTokens))
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}
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return strings.Join(bucketRepr, ", ")
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}
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func maxDuration(x time.Duration, y time.Duration) time.Duration {
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if x > y {
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return x
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}
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return y
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}
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