/
limiter.go
99 lines (87 loc) · 2.33 KB
/
limiter.go
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// Licensed to LinDB under one or more contributor
// license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright
// ownership. LinDB 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 concurrent
import (
"context"
"errors"
"sync"
"time"
"github.com/lindb/lindb/metrics"
)
var ErrConcurrencyLimiterTimeout = errors.New("reaches the max concurrency for writing")
type Limiter struct {
ctx context.Context
timeout time.Duration
tokens chan struct{}
statistics *metrics.LimitStatistics
}
// NewLimiter creates a limiter based of buffer channel.
// It limits the concurrency for writing.
func NewLimiter(ctx context.Context, maxConcurrency int, timeout time.Duration, statistics *metrics.LimitStatistics) *Limiter {
return &Limiter{
ctx: ctx,
timeout: timeout,
tokens: make(chan struct{}, maxConcurrency),
statistics: statistics,
}
}
func (l *Limiter) Do(f func() error) error {
select {
case l.tokens <- struct{}{}:
err := f()
l.statistics.Processed.Incr()
<-l.tokens
return err
default:
// tokens are taken, so waits one to be free
}
l.statistics.Throttles.Incr()
timer := acquireTimer(l.timeout)
select {
case l.tokens <- struct{}{}:
releaseTimer(timer)
err := f()
l.statistics.Processed.Incr()
<-l.tokens
return err
case <-l.ctx.Done():
return nil
case <-timer.C:
releaseTimer(timer)
l.statistics.Timeouts.Incr()
return ErrConcurrencyLimiterTimeout
}
}
var timerPool sync.Pool
func acquireTimer(d time.Duration) *time.Timer {
item := timerPool.Get()
if item == nil {
return time.NewTimer(d)
}
t := item.(*time.Timer)
// timer.Reset returns if timer is active.
if t.Reset(d) {
return time.NewTimer(d)
}
return t
}
func releaseTimer(t *time.Timer) {
if !t.Stop() {
return
}
timerPool.Put(t)
}