kubernetes time_budget 源码
kubernetes time_budget 代码
文件路径：/staging/src/k8s.io/apiserver/pkg/storage/cacher/time_budget.go
/*
Copyright 2016 The Kubernetes Authors.
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 cacher
import (
"sync"
"time"
"k8s.io/utils/clock"
)
const (
refreshPerSecond = 50 * time.Millisecond
maxBudget = 100 * time.Millisecond
)
// timeBudget implements a budget of time that you can use and is
// periodically being refreshed. The pattern to use it is:
//
// budget := newTimeBudget(...)
// ...
// timeout := budget.takeAvailable()
// // Now you can spend at most timeout on doing stuff
// ...
// // If you didn't use all timeout, return what you didn't use
// budget.returnUnused(<unused part of timeout>)
//
// NOTE: It's not recommended to be used concurrently from multiple threads -
// if first user takes the whole timeout, the second one will get 0 timeout
// even though the first one may return something later.
type timeBudget interface {
takeAvailable() time.Duration
returnUnused(unused time.Duration)
}
type timeBudgetImpl struct {
sync.Mutex
clock clock.Clock
budget time.Duration
maxBudget time.Duration
refresh time.Duration
// last store last access time
last time.Time
}
func newTimeBudget() timeBudget {
result := &timeBudgetImpl{
clock: clock.RealClock{},
budget: time.Duration(0),
refresh: refreshPerSecond,
maxBudget: maxBudget,
}
result.last = result.clock.Now()
return result
}
func (t *timeBudgetImpl) takeAvailable() time.Duration {
t.Lock()
defer t.Unlock()
// budget accumulated since last access
now := t.clock.Now()
acc := now.Sub(t.last).Seconds() * t.refresh.Seconds()
if acc < 0 {
acc = 0
}
// update current budget and store the current time
if t.budget = t.budget + time.Duration(acc*1e9); t.budget > t.maxBudget {
t.budget = t.maxBudget
}
t.last = now
result := t.budget
t.budget = time.Duration(0)
return result
}
func (t *timeBudgetImpl) returnUnused(unused time.Duration) {
t.Lock()
defer t.Unlock()
if unused < 0 {
// We used more than allowed.
return
}
// add the unused time directly to the budget
// takeAvailable() will take into account the elapsed time
if t.budget = t.budget + unused; t.budget > t.maxBudget {
t.budget = t.maxBudget
}
}
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