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periodicalexecutor.go
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periodicalexecutor.go
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package executors
import (
"reflect"
"sync"
"sync/atomic"
"time"
"github.com/tal-tech/go-zero/core/lang"
"github.com/tal-tech/go-zero/core/proc"
"github.com/tal-tech/go-zero/core/syncx"
"github.com/tal-tech/go-zero/core/threading"
"github.com/tal-tech/go-zero/core/timex"
)
const idleRound = 10
type (
// A type that satisfies executors.TaskContainer can be used as the underlying
// container that used to do periodical executions.
TaskContainer interface {
// AddTask adds the task into the container.
// Returns true if the container needs to be flushed after the addition.
AddTask(task interface{}) bool
// Execute handles the collected tasks by the container when flushing.
Execute(tasks interface{})
// RemoveAll removes the contained tasks, and return them.
RemoveAll() interface{}
}
PeriodicalExecutor struct {
commander chan interface{}
interval time.Duration
container TaskContainer
waitGroup sync.WaitGroup
// avoid race condition on waitGroup when calling wg.Add/Done/Wait(...)
wgBarrier syncx.Barrier
confirmChan chan lang.PlaceholderType
inflight int32
guarded bool
newTicker func(duration time.Duration) timex.Ticker
lock sync.Mutex
}
)
func NewPeriodicalExecutor(interval time.Duration, container TaskContainer) *PeriodicalExecutor {
executor := &PeriodicalExecutor{
// buffer 1 to let the caller go quickly
commander: make(chan interface{}, 1),
interval: interval,
container: container,
confirmChan: make(chan lang.PlaceholderType),
newTicker: func(d time.Duration) timex.Ticker {
return timex.NewTicker(d)
},
}
proc.AddShutdownListener(func() {
executor.Flush()
})
return executor
}
func (pe *PeriodicalExecutor) Add(task interface{}) {
if vals, ok := pe.addAndCheck(task); ok {
pe.commander <- vals
<-pe.confirmChan
}
}
func (pe *PeriodicalExecutor) Flush() bool {
pe.enterExecution()
return pe.executeTasks(func() interface{} {
pe.lock.Lock()
defer pe.lock.Unlock()
return pe.container.RemoveAll()
}())
}
func (pe *PeriodicalExecutor) Sync(fn func()) {
pe.lock.Lock()
defer pe.lock.Unlock()
fn()
}
func (pe *PeriodicalExecutor) Wait() {
pe.Flush()
pe.wgBarrier.Guard(func() {
pe.waitGroup.Wait()
})
}
func (pe *PeriodicalExecutor) addAndCheck(task interface{}) (interface{}, bool) {
pe.lock.Lock()
defer func() {
if !pe.guarded {
pe.guarded = true
// defer to unlock quickly
defer pe.backgroundFlush()
}
pe.lock.Unlock()
}()
if pe.container.AddTask(task) {
atomic.AddInt32(&pe.inflight, 1)
return pe.container.RemoveAll(), true
}
return nil, false
}
func (pe *PeriodicalExecutor) backgroundFlush() {
threading.GoSafe(func() {
// flush before quit goroutine to avoid missing tasks
defer pe.Flush()
ticker := pe.newTicker(pe.interval)
defer ticker.Stop()
var commanded bool
last := timex.Now()
for {
select {
case vals := <-pe.commander:
commanded = true
atomic.AddInt32(&pe.inflight, -1)
pe.enterExecution()
pe.confirmChan <- lang.Placeholder
pe.executeTasks(vals)
last = timex.Now()
case <-ticker.Chan():
if commanded {
commanded = false
} else if pe.Flush() {
last = timex.Now()
} else if pe.shallQuit(last) {
return
}
}
}
})
}
func (pe *PeriodicalExecutor) doneExecution() {
pe.waitGroup.Done()
}
func (pe *PeriodicalExecutor) enterExecution() {
pe.wgBarrier.Guard(func() {
pe.waitGroup.Add(1)
})
}
func (pe *PeriodicalExecutor) executeTasks(tasks interface{}) bool {
defer pe.doneExecution()
ok := pe.hasTasks(tasks)
if ok {
pe.container.Execute(tasks)
}
return ok
}
func (pe *PeriodicalExecutor) hasTasks(tasks interface{}) bool {
if tasks == nil {
return false
}
val := reflect.ValueOf(tasks)
switch val.Kind() {
case reflect.Array, reflect.Chan, reflect.Map, reflect.Slice:
return val.Len() > 0
default:
// unknown type, let caller execute it
return true
}
}
func (pe *PeriodicalExecutor) shallQuit(last time.Duration) (stop bool) {
if timex.Since(last) <= pe.interval*idleRound {
return
}
// checking pe.inflight and setting pe.guarded should be locked together
pe.lock.Lock()
if atomic.LoadInt32(&pe.inflight) == 0 {
pe.guarded = false
stop = true
}
pe.lock.Unlock()
return
}