Hands

“Dedicated to Brother Chang”

Hands is a process controller used to control the execution and return strategies of multiple goroutines.

Getting started

A simple example

n := 0
controller := hands.New()

controller.Do(func(ctx context.Context) error {
  n++
  return nil
})

err := controller.Run()
if err != nil {
  // ...
}

fmt.Println(n)

// Output:
// 1

Use the Do method to add a task, use the Run method to start the task(s).

TaskOption

TaskOption is used to set some metadata for the task.

func Priority(priority int32) TaskOption

Use the Priority method to set a priority for a task. The higher the priority, the higher the execution order.

(hands.P() is an alias for hands.Priority().)

controller := New()

controller.Do(func(ctx context.Context) error {
  fmt.Println("3")
  return nil
}, hands.P(1))

controller.Do(func(ctx context.Context) error {
  fmt.Println("2")
  return nil
}, hands.P(2))

controller.Do(func(ctx context.Context) error {
  fmt.Println("1")
  return nil
}, hands.P(3))

controller.Run()

// Output:
// 1
// 2
// 3

HandOption

HandOption is used to control the execution strategy of the task.

func Fastest() HandOption

Fastest(): When a task is completed, return immediately.

n := 0
controller := hands.New()

controller.Do(func(ctx context.Context) error {
  time.Sleep(time.Duration(10) * time.Millisecond)
  n += 1
  return nil
})

controller.Do(func(ctx context.Context) error {
  n += 2
  return nil
})

controller.Run(hands.Fastest())

fmt.Println(n)

// Output:
// 2

func Percentage(percentage float32) HandOption

When a certain percentage of tasks are executed, the results are returned.

n := 0
controller := hands.New()

controller.Do(func(ctx context.Context) error {
  n++
  return nil
})

controller.Do(func(ctx context.Context) error {
  n++
  return nil
})

controller.Do(func(ctx context.Context) error {
  n++
  return nil
})

controller.Do(func(ctx context.Context) error {
  n++
  return nil
})

controller.Run(hands.Percentage(0.5))

fmt.Println(n)

// Output:
// 2

func Between(l, r int32) HandOption

Between(): Only execute tasks with a priority within the specified range.

n := 0
controller := hands.New()

controller.Do(func(ctx context.Context) error {
  n += 1
  return nil
}, hands.P(1))

controller.Do(func(ctx context.Context) error {
  n += 2
  return nil
}, hands.P(2))

controller.Do(func(ctx context.Context) error {
  n += 3
  return nil
}, hands.P(3))

controller.Do(func(ctx context.Context) error {
  n += 4
  return nil
}, hands.P(4))

controller.Run(hands.Between(2, 3))

fmt.Println(n)

// Output:
// 5

Note: If the use the controller.Run() method, tasks outside the Between() will not be executed, you can use the controller.RunAll() method to allow other priority tasks to be executed asynchronously.

...
controller.RunAll(hands.Between(2, 3))

fmt.Println(n)
time.Sleep(time.Duration(10) * time.Millisecond)
fmt.Println(n)

// Output:
// 5
// 10

func In(in []int32) HandOption

In(): Only execute tasks in the specified priority list.

n := 0
controller := hands.New()

controller.Do(func(ctx context.Context) error {
  n += 1
  return nil
}, hands.P(1))

controller.Do(func(ctx context.Context) error {
  n += 2
  return nil
}, hands.P(2))

controller.Do(func(ctx context.Context) error {
  n += 3
  return nil
}, hands.P(3))

controller.Do(func(ctx context.Context) error {
  n += 4
  return nil
}, hands.P(4))

controller.Run(hands.In([]int32{2, 4}))

fmt.Println(n)

// Output:
// 6

Yes, the controller.RunAll() method can also be used here.

...
controller.RunAll(hands.In([]int32{2, 4}))

fmt.Println(n)
time.Sleep(time.Duration(10) * time.Millisecond)
fmt.Println(n)

// Output:
// 6
// 10

func WithContext(ctx context.Context) HandOption

Make the task use the specified context.

c, cancel := context.WithTimeout(context.Background(), 50*time.Millisecond)
defer cancel()

controller := hands.New()

controller.Do(func(ctx context.Context) error {
  time.Sleep(time.Duration(100) * time.Millisecond)
  return nil
})

err := controller.Run(hands.WithContext(c))

fmt.Println(err.Error())

// Output:
// context deadline exceeded

Callback after all tasks have been executed

n := 0
controller := hands.New()

controller.Do(func(ctx context.Context) error {
  time.Sleep(time.Duration(10) * time.Millisecond)
  n++
  return nil
})

controller.Do(func(ctx context.Context) error {
  time.Sleep(time.Duration(10) * time.Millisecond)
  n++
  return nil
})

controller.Do(func(ctx context.Context) error {
  n += 5
  return nil
})

// Here.
controller.Done(func() {
  // `True`
  assert.Equal(t, n, 7)
})

controller.RunAll(Fastest())

// `True`
assert.Equal(t, n, 5)
time.Sleep(time.Duration(500) * time.Millisecond)

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