fix bug #317 (#335)

* fix bug #317.
* add counter for current task. If it's bigger then zero, do not quit background thread

* Revert "fix issue #317 (#331)"

This reverts commit fc43876cc5.

core/executors/periodicalexecutor_test.go

@@ -140,25 +140,6 @@ func TestPeriodicalExecutor_WaitFast(t *testing.T) {
 	assert.Equal(t, total, cnt)
 }
 
-func TestPeriodicalExecutor_Deadlock(t *testing.T) {
-	ticker := timex.NewFakeTicker()
-	defer ticker.Stop()
-
-	exec := NewPeriodicalExecutor(time.Millisecond, newContainer(time.Millisecond, nil))
-	exec.newTicker = func(d time.Duration) timex.Ticker {
-		return ticker
-	}
-	ticker.Tick()
-	exec.lock.Lock()
-	exec.backgroundFlush()
-	time.Sleep(20 * time.Millisecond)
-	ticker.Tick()
-	exec.commander <- 1
-	exec.lock.Unlock()
-	<-exec.confirmChan
-	exec.Wait()
-}
-
 // go test -benchtime 10s -bench .
 func BenchmarkExecutor(b *testing.B) {
 	b.ReportAllocs()
@@ -168,3 +149,11 @@ func BenchmarkExecutor(b *testing.B) {
 		executor.Add(1)
 	}
 }
+
+func TestPeriodicalExecutor_Deadlock(t *testing.T) {
+	executer := NewBulkExecutor(func(tasks []interface{}) {
+	}, WithBulkTasks(1), WithBulkInterval(time.Millisecond))
+	for i := 0; i < 1e6; i++ {
+		executer.Add(1)
+	}
+}