WaitGroup 和 worker pool

• WaitGroup
• worker pool

WaitGroup

• WaitGroup 用于等待一个集合的 goroutine 执行完毕。

• WaitGroup 是一个结构体，内部使用了一个计数器，使用 Add 可以增加计数，使用 Done 可以减少计数。当计数为 0 的时候，Wait 返回

  • WaitGroup 不能使用值传递，否则会复制拷贝，将不能通知 Wait 函数

    func goroutineProccess(index int, wg *sync.WaitGroup) {
    fmt.Println("start goroutineProcess ", index)
    time.Sleep(2 * time.Second)
    fmt.Printf("Ended goroutineProcess %d\n", index)
    wg.Done()
    }
    
    func WaitgroupTest() {
    routineNumber := 3
    var wg sync.WaitGroup
    for i := 0; i < routineNumber; i++ {
    wg.Add(1)
    go goroutineProccess(i, &wg)
    }
    wg.Wait()
    fmt.Println("All goroutine exit...")
    }
    

worker pool

• worker pool 是一个线程的集合，等待分配任务执行。任务完成之后，立刻准备下一个任务

• 使用 buffered channel 实现 worker pool

  type Job struct {
  id       int
  randomno int
  }
  
  type Result struct {
  job         Job
  sumofdigits int
  }
  
  var jobs = make(chan Job, 10)
  var results = make(chan Result, 10)
  
  func digits(number int) int {
  sum := 0
  no := number
  for no != 0 {
      sum += no % 10
      no /= 10
  }
  time.Sleep(2 * time.Second)
  return sum
  }
  
  func dowork(wg *sync.WaitGroup) {
  for job := range jobs {
      sum := Result{job, digits(job.randomno)}
      results <- sum
  }
  wg.Done()
  }
  
  func createWorkerPool(noOfWorkers int) {
  var wg sync.WaitGroup
  for i := 0; i < noOfWorkers; i++ {
      wg.Add(1)
      go dowork(&wg)
  }
  wg.Wait()
  close(results)
  }
  
  func createJobs(noOfJobs int) {
  for i := 0; i < noOfJobs; i++ {
      randomno := rand.Intn(999)
      job := Job{i, randomno}
      jobs <- job
  }
  close(jobs)
  }
  
  func getResult(done chan bool) {
  for result := range results {
      fmt.Printf("Job id = %2d, randomno = %3d, result = %d\n", result.job.id, result.job.randomno, result.sumofdigits)
  }
  done <- true
  }
  
  func WokerPoolTest() {
  startTime := time.Now()
  noOfJobs := 100
  go createJobs(noOfJobs)
  noOfWorkers := 10
  go createWorkerPool(noOfWorkers)
  done := make(chan bool)
  go getResult(done)
  <-done
  endTime := time.Now()
  diff := endTime.Sub(startTime)
  fmt.Println("Cost ", diff.Seconds(), " seconds")
  }