Concurrency / Limiting concurrency with a semaphore / Essential Go
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package main
import (
"fmt"
"sync"
"time"
)
var (
semaphoreSize = 4
mu sync.Mutex
totalTasks int
curConcurrentTasks int
maxConcurrentTasks int
)
func timeConsumingTask() {
mu.Lock()
totalTasks++
curConcurrentTasks++
if curConcurrentTasks > maxConcurrentTasks {
maxConcurrentTasks = curConcurrentTasks
}
mu.Unlock()
// in real system this would be a CPU intensive operation
time.Sleep(10 * time.Millisecond)
mu.Lock()
curConcurrentTasks--
mu.Unlock()
}
func main() {
sem := make(chan struct{}, semaphoreSize)
var wg sync.WaitGroup
for i := 0; i < 32; i++ {
// acquire semaphore
sem <- struct{}{}
wg.Add(1)
go func() {
timeConsumingTask()
// release semaphore
<-sem
wg.Done()
}()
}
// wait for all task to finish
wg.Wait()
fmt.Printf("total tasks : %d\n", totalTasks)
fmt.Printf("max concurrent tasks: %d\n", maxConcurrentTasks)
}
Go
INFO