[client] Add peer conn init limit (#3001)

Limit the peer connection initialization to 200 peers at the same time

util/semaphore-group/semaphore_group_test.go

@@ -0,0 +1,66 @@
+package semaphoregroup
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+func TestSemaphoreGroup(t *testing.T) {
+	semGroup := NewSemaphoreGroup(2)
+
+	for i := 0; i < 5; i++ {
+		semGroup.Add(context.Background())
+		go func(id int) {
+			defer semGroup.Done(context.Background())
+
+			got := len(semGroup.semaphore)
+			if got == 0 {
+				t.Errorf("Expected semaphore length > 0 , got 0")
+			}
+
+			time.Sleep(time.Millisecond)
+			t.Logf("Goroutine %d is running\n", id)
+		}(i)
+	}
+
+	semGroup.Wait()
+
+	want := 0
+	got := len(semGroup.semaphore)
+	if got != want {
+		t.Errorf("Expected semaphore length %d, got %d", want, got)
+	}
+}
+
+func TestSemaphoreGroupContext(t *testing.T) {
+	semGroup := NewSemaphoreGroup(1)
+	semGroup.Add(context.Background())
+	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
+	t.Cleanup(cancel)
+	rChan := make(chan struct{})
+
+	go func() {
+		semGroup.Add(ctx)
+		rChan <- struct{}{}
+	}()
+	select {
+	case <-rChan:
+	case <-time.NewTimer(2 * time.Second).C:
+		t.Error("Adding to semaphore group should not block when context is not done")
+	}
+
+	semGroup.Done(context.Background())
+
+	ctxDone, cancelDone := context.WithTimeout(context.Background(), 1*time.Second)
+	t.Cleanup(cancelDone)
+	go func() {
+		semGroup.Done(ctxDone)
+		rChan <- struct{}{}
+	}()
+	select {
+	case <-rChan:
+	case <-time.NewTimer(2 * time.Second).C:
+		t.Error("Releasing from semaphore group should not block when context is not done")
+	}
+}