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// _ _
// __ _____ __ ___ ___ __ _| |_ ___
// \ \ /\ / / _ \/ _` \ \ / / |/ _` | __/ _ \
// \ V V / __/ (_| |\ V /| | (_| | || __/
// \_/\_/ \___|\__,_| \_/ |_|\__,_|\__\___|
//
// Copyright © 2016 - 2024 Weaviate B.V. All rights reserved.
//
// CONTACT: [email protected]
//
package ratelimiter
import "sync/atomic"
// Limiter is a thread-safe counter that can be used for rate-limiting requests
type Limiter struct {
max int64
current int64
}
// New creates a [Limiter] with the specified maximum concurrent requests
func New(maxRequests int) *Limiter {
return &Limiter{
max: int64(maxRequests),
}
}
// If there is still room, TryInc, increases the counter and returns true. If
// there are too many concurrent requests it does not increase the counter and
// returns false
func (l *Limiter) TryInc() bool {
if l.max <= 0 {
return true
}
new := atomic.AddInt64(&l.current, 1)
if new <= l.max {
return true
}
// undo unsuccessful increment
atomic.AddInt64(&l.current, -1)
return false
}
func (l *Limiter) Dec() {
if l.max <= 0 {
return
}
new := atomic.AddInt64(&l.current, -1)
if new < 0 {
// Should not happen unless some client called Dec multiple times.
// Try to reset current to 0. It's ok if swap doesn't happen, since
// someone else must've succeeded at fixing current value.
atomic.CompareAndSwapInt64(&l.current, new, 0)
}
}
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