Lesson 23

lesson23/info.txt

@@ -0,0 +1,10 @@
+Context:
+a) Хранить значения
+b) Сообщать о завершении
+
+1. Background, TODO
+2. With value
+3. With cancel
+4. With deadline/timeout
+
+5. Worker pool

lesson23/main.go

@@ -0,0 +1,96 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"runtime"
+	"sync"
+	"time"
+)
+
+func main() {
+	//baseKnowledge()
+	workerPool()
+}
+
+func baseKnowledge() {
+	ctx := context.Background()
+	fmt.Println(ctx)
+
+	toDo := context.TODO()
+	fmt.Println(toDo)
+
+	withValue := context.WithValue(ctx, "name", "vasya")
+	fmt.Println(withValue.Value("name"))
+
+	withCancel, cancel := context.WithCancel(ctx)
+	fmt.Println(withCancel.Err())
+	cancel()
+	fmt.Println(withCancel.Err())
+
+	withDeadline, cancel := context.WithDeadline(ctx, time.Now().Add(time.Second*3))
+	defer cancel()
+	fmt.Println(withDeadline.Deadline())
+	fmt.Println(withDeadline.Err())
+	fmt.Println(<-withDeadline.Done())
+
+	withTimeout, cancel := context.WithTimeout(ctx, time.Second*2)
+	defer cancel()
+	fmt.Println(withTimeout.Done())
+}
+
+func workerPool() {
+
+	ctx, cancel := context.WithCancel(context.Background())
+	ctx, cancel = context.WithTimeout(context.Background(), time.Millisecond*20)
+	defer cancel()
+
+	wg := &sync.WaitGroup{}
+	numbersToProcess, processedNumbers := make(chan int, 5), make(chan int, 5)
+
+	for i := 0; i <= runtime.NumCPU(); i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			worker(ctx, numbersToProcess, processedNumbers)
+		}()
+	}
+
+	go func() {
+		for i := 0; i < 1000; i++ {
+			/*if i == 500 {
+				cancel()
+			}*/
+			numbersToProcess <- i
+		}
+		close(numbersToProcess)
+	}()
+
+	go func() {
+		wg.Wait()
+		close(processedNumbers)
+	}()
+
+	var counter int
+	for resultValue := range processedNumbers {
+		counter++
+		fmt.Println(resultValue)
+	}
+
+	fmt.Println(counter)
+}
+
+func worker(ctx context.Context, toProcess <-chan int, processed chan<- int) {
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case value, ok := <-toProcess:
+			if !ok {
+				return
+			}
+			time.Sleep(time.Millisecond)
+			processed <- value * value
+		}
+	}
+}