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timingwheel.go
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timingwheel.go
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package collection
import (
"container/list"
"fmt"
"time"
"github.com/zeromicro/go-zero/core/lang"
"github.com/zeromicro/go-zero/core/threading"
"github.com/zeromicro/go-zero/core/timex"
)
const drainWorkers = 8
type (
// Execute defines the method to execute the task.
Execute func(key, value interface{})
// A TimingWheel is a timing wheel object to schedule tasks.
TimingWheel struct {
interval time.Duration
ticker timex.Ticker
slots []*list.List
timers *SafeMap
tickedPos int
numSlots int
execute Execute
setChannel chan timingEntry
moveChannel chan baseEntry
removeChannel chan interface{}
drainChannel chan func(key, value interface{})
stopChannel chan lang.PlaceholderType
}
timingEntry struct {
baseEntry
value interface{}
circle int
diff int
removed bool
}
baseEntry struct {
delay time.Duration
key interface{}
}
positionEntry struct {
pos int
item *timingEntry
}
timingTask struct {
key interface{}
value interface{}
}
)
// NewTimingWheel returns a TimingWheel.
func NewTimingWheel(interval time.Duration, numSlots int, execute Execute) (*TimingWheel, error) {
if interval <= 0 || numSlots <= 0 || execute == nil {
return nil, fmt.Errorf("interval: %v, slots: %d, execute: %p", interval, numSlots, execute)
}
return newTimingWheelWithClock(interval, numSlots, execute, timex.NewTicker(interval))
}
func newTimingWheelWithClock(interval time.Duration, numSlots int, execute Execute, ticker timex.Ticker) (
*TimingWheel, error) {
tw := &TimingWheel{
interval: interval,
ticker: ticker,
slots: make([]*list.List, numSlots),
timers: NewSafeMap(),
tickedPos: numSlots - 1, // at previous virtual circle
execute: execute,
numSlots: numSlots,
setChannel: make(chan timingEntry),
moveChannel: make(chan baseEntry),
removeChannel: make(chan interface{}),
drainChannel: make(chan func(key, value interface{})),
stopChannel: make(chan lang.PlaceholderType),
}
tw.initSlots()
go tw.run()
return tw, nil
}
// Drain drains all items and executes them.
func (tw *TimingWheel) Drain(fn func(key, value interface{})) {
tw.drainChannel <- fn
}
// MoveTimer moves the task with the given key to the given delay.
func (tw *TimingWheel) MoveTimer(key interface{}, delay time.Duration) {
if delay <= 0 || key == nil {
return
}
tw.moveChannel <- baseEntry{
delay: delay,
key: key,
}
}
// RemoveTimer removes the task with the given key.
func (tw *TimingWheel) RemoveTimer(key interface{}) {
if key == nil {
return
}
tw.removeChannel <- key
}
// SetTimer sets the task value with the given key to the delay.
func (tw *TimingWheel) SetTimer(key, value interface{}, delay time.Duration) {
if delay <= 0 || key == nil {
return
}
tw.setChannel <- timingEntry{
baseEntry: baseEntry{
delay: delay,
key: key,
},
value: value,
}
}
// Stop stops tw.
func (tw *TimingWheel) Stop() {
close(tw.stopChannel)
}
func (tw *TimingWheel) drainAll(fn func(key, value interface{})) {
runner := threading.NewTaskRunner(drainWorkers)
for _, slot := range tw.slots {
for e := slot.Front(); e != nil; {
task := e.Value.(*timingEntry)
next := e.Next()
slot.Remove(e)
e = next
if !task.removed {
runner.Schedule(func() {
fn(task.key, task.value)
})
}
}
}
}
func (tw *TimingWheel) getPositionAndCircle(d time.Duration) (pos, circle int) {
steps := int(d / tw.interval)
pos = (tw.tickedPos + steps) % tw.numSlots
circle = (steps - 1) / tw.numSlots
return
}
func (tw *TimingWheel) initSlots() {
for i := 0; i < tw.numSlots; i++ {
tw.slots[i] = list.New()
}
}
func (tw *TimingWheel) moveTask(task baseEntry) {
val, ok := tw.timers.Get(task.key)
if !ok {
return
}
timer := val.(*positionEntry)
if task.delay < tw.interval {
threading.GoSafe(func() {
tw.execute(timer.item.key, timer.item.value)
})
return
}
pos, circle := tw.getPositionAndCircle(task.delay)
if pos >= timer.pos {
timer.item.circle = circle
timer.item.diff = pos - timer.pos
} else if circle > 0 {
circle--
timer.item.circle = circle
timer.item.diff = tw.numSlots + pos - timer.pos
} else {
timer.item.removed = true
newItem := &timingEntry{
baseEntry: task,
value: timer.item.value,
}
tw.slots[pos].PushBack(newItem)
tw.setTimerPosition(pos, newItem)
}
}
func (tw *TimingWheel) onTick() {
tw.tickedPos = (tw.tickedPos + 1) % tw.numSlots
l := tw.slots[tw.tickedPos]
tw.scanAndRunTasks(l)
}
func (tw *TimingWheel) removeTask(key interface{}) {
val, ok := tw.timers.Get(key)
if !ok {
return
}
timer := val.(*positionEntry)
timer.item.removed = true
tw.timers.Del(key)
}
func (tw *TimingWheel) run() {
for {
select {
case <-tw.ticker.Chan():
tw.onTick()
case task := <-tw.setChannel:
tw.setTask(&task)
case key := <-tw.removeChannel:
tw.removeTask(key)
case task := <-tw.moveChannel:
tw.moveTask(task)
case fn := <-tw.drainChannel:
tw.drainAll(fn)
case <-tw.stopChannel:
tw.ticker.Stop()
return
}
}
}
func (tw *TimingWheel) runTasks(tasks []timingTask) {
if len(tasks) == 0 {
return
}
go func() {
for i := range tasks {
threading.RunSafe(func() {
tw.execute(tasks[i].key, tasks[i].value)
})
}
}()
}
func (tw *TimingWheel) scanAndRunTasks(l *list.List) {
var tasks []timingTask
for e := l.Front(); e != nil; {
task := e.Value.(*timingEntry)
if task.removed {
next := e.Next()
l.Remove(e)
e = next
continue
} else if task.circle > 0 {
task.circle--
e = e.Next()
continue
} else if task.diff > 0 {
next := e.Next()
l.Remove(e)
// (tw.tickedPos+task.diff)%tw.numSlots
// cannot be the same value of tw.tickedPos
pos := (tw.tickedPos + task.diff) % tw.numSlots
tw.slots[pos].PushBack(task)
tw.setTimerPosition(pos, task)
task.diff = 0
e = next
continue
}
tasks = append(tasks, timingTask{
key: task.key,
value: task.value,
})
next := e.Next()
l.Remove(e)
tw.timers.Del(task.key)
e = next
}
tw.runTasks(tasks)
}
func (tw *TimingWheel) setTask(task *timingEntry) {
if task.delay < tw.interval {
task.delay = tw.interval
}
if val, ok := tw.timers.Get(task.key); ok {
entry := val.(*positionEntry)
entry.item.value = task.value
tw.moveTask(task.baseEntry)
} else {
pos, circle := tw.getPositionAndCircle(task.delay)
task.circle = circle
tw.slots[pos].PushBack(task)
tw.setTimerPosition(pos, task)
}
}
func (tw *TimingWheel) setTimerPosition(pos int, task *timingEntry) {
if val, ok := tw.timers.Get(task.key); ok {
timer := val.(*positionEntry)
timer.item = task
timer.pos = pos
} else {
tw.timers.Set(task.key, &positionEntry{
pos: pos,
item: task,
})
}
}