聊聊gost的GenericTaskPool

序

本文主要研究一下gost的GenericTaskPool

GenericTaskPool

gost/sync/task_pool.go

// GenericTaskPool represents an generic task pool.
type GenericTaskPool interface {
    // AddTask wait idle worker add task
    AddTask(t task) bool
    // AddTaskAlways add task to queues or do it immediately
    AddTaskAlways(t task)
    // AddTaskBalance add task to idle queue
    AddTaskBalance(t task)
    // Close use to close the task pool
    Close()
    // IsClosed use to check pool status.
    IsClosed() bool
}

GenericTaskPool接口定义了AddTask、AddTaskAlways、AddTaskBalance、Close、IsClosed接口

TaskPool

gost/sync/task_pool.go

type TaskPool struct {
    TaskPoolOptions

    idx    uint32 // round robin index
    qArray []chan task
    wg     sync.WaitGroup

    once sync.Once
    done chan struct{}
}

// return false when the pool is stop
func (p *TaskPool) AddTask(t task) (ok bool) {
    idx := atomic.AddUint32(&p.idx, 1)
    id := idx % uint32(p.tQNumber)

    select {
    case <-p.done:
        return false
    default:
        p.qArray[id] <- t
        return true
    }
}

func (p *TaskPool) AddTaskAlways(t task) {
    id := atomic.AddUint32(&p.idx, 1) % uint32(p.tQNumber)

    select {
    case p.qArray[id] <- t:
        return
    default:
        goSafely(t)
    }
}

// do it immediately when no idle queue
func (p *TaskPool) AddTaskBalance(t task) {
    length := len(p.qArray)

    // try len/2 times to lookup idle queue
    for i := 0; i < length/2; i++ {
        select {
        case p.qArray[rand.Intn(length)] <- t:
            return
        default:
            continue
        }
    }

    goSafely(t)
}

// check whether the session has been closed.
func (p *TaskPool) IsClosed() bool {
    select {
    case <-p.done:
        return true

    default:
        return false
    }
}

func (p *TaskPool) Close() {
    p.stop()
    p.wg.Wait()
    for i := range p.qArray {
        close(p.qArray[i])
    }
}

TaskPool定义了TaskPoolOptions、idx、qArray、wg、once、done属性；它实现了GenericTaskPool接口；AddTask方法在pool是done的时候会返回false，其余情况会递增idx，然后根据tQNumber计算id，往qArray[id]写入task；AddTaskAlways方法会忽略pool的关闭信息；AddTaskBalance方法会尝试len/2次随机往qArray写入task，都写入不成功则goSafely执行；IsClosed主要是读取done的channel信息；Close方法执行stop及wg.Wait()，最后遍历qArray挨个执行close

NewTaskPool

gost/sync/task_pool.go

func NewTaskPool(opts ...TaskPoolOption) GenericTaskPool {
    var tOpts TaskPoolOptions
    for _, opt := range opts {
        opt(&tOpts)
    }

    tOpts.validate()

    p := &TaskPool{
        TaskPoolOptions: tOpts,
        qArray:          make([]chan task, tOpts.tQNumber),
        done:            make(chan struct{}),
    }

    for i := 0; i < p.tQNumber; i++ {
        p.qArray[i] = make(chan task, p.tQLen)
    }
    p.start()

    return p
}

NewTaskPool通过TaskPoolOptions来创建TaskPool

TaskPoolOption

gost/sync/options.go

const (
    defaultTaskQNumber = 10
    defaultTaskQLen    = 128
)

/////////////////////////////////////////
// Task Pool Options
/////////////////////////////////////////

// TaskPoolOptions is optional settings for task pool
type TaskPoolOptions struct {
    tQLen      int // task queue length. buffer size per queue
    tQNumber   int // task queue number. number of queue
    tQPoolSize int // task pool size. number of workers
}

func (o *TaskPoolOptions) validate() {
    if o.tQPoolSize < 1 {
        panic(fmt.Sprintf("illegal pool size %d", o.tQPoolSize))
    }

    if o.tQLen < 1 {
        o.tQLen = defaultTaskQLen
    }

    if o.tQNumber < 1 {
        o.tQNumber = defaultTaskQNumber
    }

    if o.tQNumber > o.tQPoolSize {
        o.tQNumber = o.tQPoolSize
    }
}

type TaskPoolOption func(*TaskPoolOptions)

// WithTaskPoolTaskPoolSize set @size of the task queue pool size
func WithTaskPoolTaskPoolSize(size int) TaskPoolOption {
    return func(o *TaskPoolOptions) {
        o.tQPoolSize = size
    }
}

// WithTaskPoolTaskQueueLength set @length of the task queue length
func WithTaskPoolTaskQueueLength(length int) TaskPoolOption {
    return func(o *TaskPoolOptions) {
        o.tQLen = length
    }
}

// WithTaskPoolTaskQueueNumber set @number of the task queue number
func WithTaskPoolTaskQueueNumber(number int) TaskPoolOption {
    return func(o *TaskPoolOptions) {
        o.tQNumber = number
    }
}

TaskPoolOptions定义了tQLen、tQNumber、tQPoolSize属性，提供了WithTaskPoolTaskPoolSize、WithTaskPoolTaskQueueLength、WithTaskPoolTaskQueueNumber、validate方法

start

gost/sync/task_pool.go

func (p *TaskPool) start() {
    for i := 0; i < p.tQPoolSize; i++ {
        p.wg.Add(1)
        workerID := i
        q := p.qArray[workerID%p.tQNumber]
        p.safeRun(workerID, q)
    }
}

func (p *TaskPool) safeRun(workerID int, q chan task) {
    gxruntime.GoSafely(nil, false,
        func() {
            err := p.run(int(workerID), q)
            if err != nil {
                // log error to stderr
                log.Printf("gost/TaskPool.run error: %s", err.Error())
            }
        },
        nil,
    )
}

start方法根据tQPoolSize挨个执行safeRun；safeRun方法通过GoSafely执行p.run(int(workerID), q)

run

gost/sync/task_pool.go

// worker
func (p *TaskPool) run(id int, q chan task) error {
    defer p.wg.Done()

    var (
        ok bool
        t  task
    )

    for {
        select {
        case <-p.done:
            if 0 < len(q) {
                return fmt.Errorf("task worker %d exit now while its task buffer length %d is greater than 0",
                    id, len(q))
            }

            return nil

        case t, ok = <-q:
            if ok {
                func() {
                    defer func() {
                        if r := recover(); r != nil {
                            fmt.Fprintf(os.Stderr, "%s goroutine panic: %v\n%s\n",
                                time.Now(), r, string(debug.Stack()))
                        }
                    }()
                    t()
                }()
            }
        }
    }
}

run方法通过for循环进行select，若读取到p.done则退出循环；若是读取到task则执行task

taskPoolSimple

gost/sync/task_pool.go

type taskPoolSimple struct {
    work chan task     // task channel
    sem  chan struct{} // gr pool size

    wg sync.WaitGroup

    once sync.Once
    done chan struct{}
}

taskPoolSimple定义了work、sem、wg、once、done属性；它实现了GenericTaskPool接口；AddTask方法先判断done，之后写入work及sem；AddTaskAlways方法在select不到channel的时候会执行goSafely；AddTaskBalance方法实际执行的是AddTaskAlways；IsClosed方法读取done信息；Close方法执行stop及wg.Wait()

实例

gost/sync/task_pool_test.go

func TestTaskPool(t *testing.T) {
    numCPU := runtime.NumCPU()
    //taskCnt := int64(numCPU * numCPU * 100)

    tp := NewTaskPool(
        WithTaskPoolTaskPoolSize(1),
        WithTaskPoolTaskQueueNumber(1),
        WithTaskPoolTaskQueueLength(1),
    )

    //task, cnt := newCountTask()
    task, _ := newCountTask()

    var wg sync.WaitGroup
    for i := 0; i < numCPU*numCPU; i++ {
        wg.Add(1)
        go func() {
            for j := 0; j < 100; j++ {
                ok := tp.AddTask(task)
                if !ok {
                    t.Log(j)
                }
            }
            wg.Done()
        }()
    }
    wg.Wait()
    tp.Close()

    //if taskCnt != atomic.LoadInt64(cnt) {
    //    //t.Error("want ", taskCnt, " got ", *cnt)
    //}
}

func TestTaskPoolSimple(t *testing.T) {
    numCPU := runtime.NumCPU()
    taskCnt := int64(numCPU * numCPU * 100)

    tp := NewTaskPoolSimple(1)

    task, cnt := newCountTask()

    var wg sync.WaitGroup
    for i := 0; i < numCPU*numCPU; i++ {
        wg.Add(1)
        go func() {
            for j := 0; j < 100; j++ {
                ok := tp.AddTask(task)
                if !ok {
                    t.Log(j)
                }
            }
            wg.Done()
        }()
    }
    wg.Wait()

    cntValue := atomic.LoadInt64(cnt)
    if taskCnt != cntValue {
        t.Error("want ", taskCnt, " got ", cntValue)
    }
}

TaskPoolSimple的创建比较简单，只需要提供size参数即可；TaskPool的创建需要提供TaskPoolOption，有WithTaskPoolTaskPoolSize、WithTaskPoolTaskQueueNumber、WithTaskPoolTaskQueueLength这些option

小结

gost的GenericTaskPool接口定义了AddTask、AddTaskAlways、AddTaskBalance、Close、IsClosed接口；这里有TaskPool、taskPoolSimple两个实现。

doc

• gost