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timerGate.go
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timerGate.go
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// Copyright (c) 2017 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package history
import (
"sync"
"time"
)
type (
// TimerGate interface
TimerGate interface {
// FireChan return the channel which will be fired when time is up
FireChan() <-chan struct{}
// FireAfter check will the timer get fired after a certain time
FireAfter(now time.Time) bool
// Update update the timer gate, return true if update is a success
// success means timer is idle or timer is set with a sooner time to fire
Update(nextTime time.Time) bool
}
// LocalTimerGate interface
LocalTimerGate interface {
TimerGate
// Close shutdown the timer
Close()
}
// LocalTimerGateImpl is an timer implementation,
// which basically is an wrapper of golang's timer and
// additional feature
LocalTimerGateImpl struct {
// the channel which will be used to proxy the fired timer
fireChan chan struct{}
closeChan chan struct{}
// the actual timer which will fire
timer *time.Timer
// variable indicating when the above timer will fire
nextWakeupTime time.Time
}
// RemoteTimerGate interface
RemoteTimerGate interface {
TimerGate
// SetCurrentTime set the current time, and additionally fire the fire chan
// if new "current" time is after the next wake up time, return true if
// "current" is antually updated
SetCurrentTime(nextTime time.Time) bool
}
// RemoteTimerGateImpl is an timer implementation,
// which basically is an wrapper of golang's timer and
// additional feature
RemoteTimerGateImpl struct {
// the channel which will be used to proxy the fired timer
fireChan chan struct{}
// lock for timer and next wake up time
sync.Mutex
// view of current time
currentTime time.Time
// time which timer will fire
nextWakeupTime time.Time
}
)
// NewLocalTimerGate create a new timer gate instance
func NewLocalTimerGate() LocalTimerGate {
timer := &LocalTimerGateImpl{
timer: time.NewTimer(0),
nextWakeupTime: time.Time{},
fireChan: make(chan struct{}, 1),
closeChan: make(chan struct{}),
}
// the timer should be stopped when initialized
if !timer.timer.Stop() {
// drain the existing signal if exist
<-timer.timer.C
}
go func() {
defer close(timer.fireChan)
defer timer.timer.Stop()
loop:
for {
select {
case <-timer.timer.C:
select {
// re-transmit on gateC
case timer.fireChan <- struct{}{}:
default:
}
case <-timer.closeChan:
// closed; cleanup and quit
break loop
}
}
}()
return timer
}
// FireChan return the channel which will be fired when time is up
func (timerGate *LocalTimerGateImpl) FireChan() <-chan struct{} {
return timerGate.fireChan
}
// FireAfter check will the timer get fired after a certain time
func (timerGate *LocalTimerGateImpl) FireAfter(now time.Time) bool {
return timerGate.nextWakeupTime.After(now)
}
// Update update the timer gate, return true if update is a success
// success means timer is idle or timer is set with a sooner time to fire
func (timerGate *LocalTimerGateImpl) Update(nextTime time.Time) bool {
// NOTE: negative duration will make the timer fire immediately
now := time.Now()
if timerGate.timer.Stop() && timerGate.nextWakeupTime.Before(nextTime) {
// this means the timer, before stopped, is active && next wake up time do not have to be updated
timerGate.timer.Reset(timerGate.nextWakeupTime.Sub(now))
return false
}
// this means the timer, before stopped, is active && next wake up time has to be updated
// or this means the timer, before stopped, is already fired / never active
timerGate.nextWakeupTime = nextTime
timerGate.timer.Reset(nextTime.Sub(now))
// Notifies caller that next notification is reset to fire at passed in 'next' visibility time
return true
}
// Close shutdown the timer
func (timerGate *LocalTimerGateImpl) Close() {
close(timerGate.closeChan)
}
// NewRemoteTimerGate create a new timer gate instance
func NewRemoteTimerGate() RemoteTimerGate {
timer := &RemoteTimerGateImpl{
currentTime: time.Time{},
nextWakeupTime: time.Time{},
fireChan: make(chan struct{}, 1),
}
return timer
}
// FireChan return the channel which will be fired when time is up
func (timerGate *RemoteTimerGateImpl) FireChan() <-chan struct{} {
return timerGate.fireChan
}
// FireAfter check will the timer get fired after a certain time
func (timerGate *RemoteTimerGateImpl) FireAfter(now time.Time) bool {
timerGate.Lock()
defer timerGate.Unlock()
active := timerGate.currentTime.Before(timerGate.nextWakeupTime)
return active && timerGate.nextWakeupTime.After(now)
}
// Update update the timer gate, return true if update is a success
// success means timer is idle or timer is set with a sooner time to fire
func (timerGate *RemoteTimerGateImpl) Update(nextTime time.Time) bool {
timerGate.Lock()
defer timerGate.Unlock()
active := timerGate.currentTime.Before(timerGate.nextWakeupTime)
if active {
if timerGate.nextWakeupTime.Before(nextTime) {
// current time < next wake up time < next time
return false
}
if timerGate.currentTime.Before(nextTime) {
// current time < next time <= next wake up time
timerGate.nextWakeupTime = nextTime
return true
}
// next time <= current time < next wake up time
timerGate.nextWakeupTime = nextTime
timerGate.fire()
return true
}
// this means the timer, before stopped, has already fired / never active
if !timerGate.currentTime.Before(nextTime) {
// next time is <= current time, need to fire immediately
// whether to update next wake up time or not is irrelevent
timerGate.fire()
} else {
// next time > current time
timerGate.nextWakeupTime = nextTime
}
return true
}
// SetCurrentTime set the current time, and additionally fire the fire chan
// if new "current" time is after the next wake up time, return true if
// "current" is actually updated
func (timerGate *RemoteTimerGateImpl) SetCurrentTime(currentTime time.Time) bool {
timerGate.Lock()
defer timerGate.Unlock()
if !timerGate.currentTime.Before(currentTime) {
// new current time is <= current time
return false
}
// NOTE: do not update the current time now
if !timerGate.currentTime.Before(timerGate.nextWakeupTime) {
// current time already >= next wakeup time
// avoid duplicate fire
timerGate.currentTime = currentTime
return true
}
timerGate.currentTime = currentTime
if !timerGate.currentTime.Before(timerGate.nextWakeupTime) {
timerGate.fire()
}
return true
}
func (timerGate *RemoteTimerGateImpl) fire() {
select {
case timerGate.fireChan <- struct{}{}:
// timer successfully triggered
default:
// timer already triggered, pass
}
}