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package mesh
import (
"time"
)
// TokenBucket acts as a rate-limiter.
// It is not safe for concurrent use by multiple goroutines.
type tokenBucket struct {
capacity int64 // Maximum capacity of bucket
tokenInterval time.Duration // Token replenishment rate
refillDuration time.Duration // Time to refill from empty
earliestUnspentToken time.Time
}
// newTokenBucket returns a bucket containing capacity tokens, refilled at a
// rate of one token per tokenInterval.
func newTokenBucket(capacity int64, tokenInterval time.Duration) *tokenBucket {
tb := tokenBucket{
capacity: capacity,
tokenInterval: tokenInterval,
refillDuration: tokenInterval * time.Duration(capacity)}
tb.earliestUnspentToken = tb.capacityToken()
return &tb
}
// Blocks until there is a token available.
// Not safe for concurrent use by multiple goroutines.
func (tb *tokenBucket) wait() {
// If earliest unspent token is in the future, sleep until then
time.Sleep(tb.earliestUnspentToken.Sub(time.Now()))
// Alternatively, enforce bucket capacity if necessary
capacityToken := tb.capacityToken()
if tb.earliestUnspentToken.Before(capacityToken) {
tb.earliestUnspentToken = capacityToken
}
// 'Remove' a token from the bucket
tb.earliestUnspentToken = tb.earliestUnspentToken.Add(tb.tokenInterval)
}
// Determine the historic token timestamp representing a full bucket
func (tb *tokenBucket) capacityToken() time.Time {
return time.Now().Add(-tb.refillDuration).Truncate(tb.tokenInterval)
}
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