83 lines
1.9 KiB
Go
83 lines
1.9 KiB
Go
// Copyright 2023 PingCAP, Inc.
|
|
//
|
|
// Licensed 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 membuf
|
|
|
|
import (
|
|
"sync"
|
|
|
|
"github.com/pingcap/log"
|
|
"go.uber.org/zap"
|
|
)
|
|
|
|
// Limiter will block on Acquire if the number it has acquired and not released
|
|
// exceeds the limit.
|
|
type Limiter struct {
|
|
initLimit int
|
|
limit int
|
|
mu sync.Mutex
|
|
waitNums []int
|
|
waitChs []chan struct{}
|
|
}
|
|
|
|
// NewLimiter creates a new Limiter with the given limit.
|
|
func NewLimiter(limit int) *Limiter {
|
|
return &Limiter{limit: limit, initLimit: limit}
|
|
}
|
|
|
|
// Acquire acquires n tokens from the limiter. If the number of tokens acquired
|
|
// and not released exceeds the limit, it will block until enough tokens are
|
|
// released.
|
|
func (l *Limiter) Acquire(n int) {
|
|
l.mu.Lock()
|
|
|
|
if l.limit >= n {
|
|
l.limit -= n
|
|
l.mu.Unlock()
|
|
return
|
|
}
|
|
|
|
waitCh := make(chan struct{})
|
|
l.waitNums = append(l.waitNums, n)
|
|
l.waitChs = append(l.waitChs, waitCh)
|
|
l.mu.Unlock()
|
|
|
|
<-waitCh
|
|
}
|
|
|
|
// Release releases tokens to the limiter. If there are goroutines waiting for
|
|
// tokens, it will wake them up.
|
|
func (l *Limiter) Release(n int) {
|
|
l.mu.Lock()
|
|
|
|
l.limit += n
|
|
if l.limit > l.initLimit {
|
|
log.Error(
|
|
"limit overflow",
|
|
zap.Int("limit", l.limit),
|
|
zap.Int("initLimit", l.initLimit),
|
|
zap.Stack("stack"),
|
|
)
|
|
}
|
|
|
|
for len(l.waitNums) > 0 && l.limit >= l.waitNums[0] {
|
|
l.limit -= l.waitNums[0]
|
|
close(l.waitChs[0])
|
|
l.waitNums = l.waitNums[1:]
|
|
l.waitChs = l.waitChs[1:]
|
|
}
|
|
|
|
l.mu.Unlock()
|
|
}
|