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qpslimiter.go
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qpslimiter.go
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package limit
import (
"errors"
"sync"
"time"
)
// QPSLimiter limiter
type QPSLimiter struct {
maxAllows int64
periodMicros int64
nextPeriodMicros int64
currentPermits int64
start time.Time
mutex sync.Mutex
}
// NewQPSLimiter new
func NewQPSLimiter(maxAllows int64, periodMs int64) (*QPSLimiter, error) {
if maxAllows < 0 || periodMs <= 0 {
return nil, errors.New("maxAllows must not be negtive, and periodMs be positive")
}
l := &QPSLimiter{
maxAllows: maxAllows,
periodMicros: periodMs * int64(time.Millisecond),
start: time.Now(),
}
l.nextPeriodMicros = int64(time.Since(l.start)) + l.periodMicros
return l, nil
}
// TryAcquire limit
func (l *QPSLimiter) TryAcquire() bool {
if l.maxAllows <= 0 {
return false
}
l.mutex.Lock()
defer l.mutex.Unlock()
var nowMicros = int64(time.Since(l.start))
if nowMicros >= l.nextPeriodMicros {
l.nextPeriodMicros = ((nowMicros-l.nextPeriodMicros)/l.periodMicros+1)*l.periodMicros + l.nextPeriodMicros
l.currentPermits = 0
}
l.currentPermits++
return l.currentPermits <= l.maxAllows
}