Fix queue test (#30646)

Fix #30643

The old test code is not stable due to the data-race described in the
TODO added at that time.

Make it stable, and remove a debug-only field from old test code.

modules/queue/workergroup.go

@@ -63,6 +63,8 @@ func (q *WorkerPoolQueue[T]) doDispatchBatchToWorker(wg *workerGroup[T], flushCh
 	// TODO: the logic could be improved in the future, to avoid a data-race between "doStartNewWorker" and "workerNum"
 	// The root problem is that if we skip "doStartNewWorker" here, the "workerNum" might be decreased by other workers later
 	// So ideally, it should check whether there are enough workers by some approaches, and start new workers if necessary.
+	// This data-race is not serious, as long as a new worker will be started soon to make sure there are enough workers,
+	// so no need to hugely refactor at the moment.
 	q.workerNumMu.Lock()
 	noWorker := q.workerNum == 0
 	if full || noWorker {
@@ -136,6 +138,14 @@ func (q *WorkerPoolQueue[T]) basePushForShutdown(items ...T) bool {
 	return true
 }
 
+func resetIdleTicker(t *time.Ticker, dur time.Duration) {
+	t.Reset(dur)
+	select {
+	case <-t.C:
+	default:
+	}
+}
+
 // doStartNewWorker starts a new worker for the queue, the worker reads from worker's channel and handles the items.
 func (q *WorkerPoolQueue[T]) doStartNewWorker(wp *workerGroup[T]) {
 	wp.wg.Add(1)
@@ -146,8 +156,6 @@ func (q *WorkerPoolQueue[T]) doStartNewWorker(wp *workerGroup[T]) {
 		log.Debug("Queue %q starts new worker", q.GetName())
 		defer log.Debug("Queue %q stops idle worker", q.GetName())
 
-		atomic.AddInt32(&q.workerStartedCounter, 1) // Only increase counter, used for debugging
-
 		t := time.NewTicker(workerIdleDuration)
 		defer t.Stop()
 
@@ -169,11 +177,7 @@ func (q *WorkerPoolQueue[T]) doStartNewWorker(wp *workerGroup[T]) {
 				}
 				q.doWorkerHandle(batch)
 				// reset the idle ticker, and drain the tick after reset in case a tick is already triggered
-				t.Reset(workerIdleDuration)
-				select {
-				case <-t.C:
-				default:
-				}
+				resetIdleTicker(t, workerIdleDuration) // key code for TestWorkerPoolQueueWorkerIdleReset
 			case <-t.C:
 				q.workerNumMu.Lock()
 				keepWorking = q.workerNum <= 1 // keep the last worker running

modules/queue/workerqueue.go

@@ -40,8 +40,6 @@ type WorkerPoolQueue[T any] struct {
 	workerMaxNum    int
 	workerActiveNum int
 	workerNumMu     sync.Mutex
-
-	workerStartedCounter int32
 }
 
 type flushType chan struct{}

modules/queue/workerqueue_test.go

@@ -5,8 +5,10 @@ package queue
 
 import (
 	"context"
+	"slices"
 	"strconv"
 	"sync"
+	"sync/atomic"
 	"testing"
 	"time"
 
@@ -250,23 +252,34 @@ func TestWorkerPoolQueueShutdown(t *testing.T) {
 
 func TestWorkerPoolQueueWorkerIdleReset(t *testing.T) {
 	defer test.MockVariableValue(&workerIdleDuration, 10*time.Millisecond)()
-	defer mockBackoffDuration(10 * time.Millisecond)()
+	defer mockBackoffDuration(5 * time.Millisecond)()
 
+	var q *WorkerPoolQueue[int]
+	var handledCount atomic.Int32
+	var hasOnlyOneWorkerRunning atomic.Bool
 	handler := func(items ...int) (unhandled []int) {
-		time.Sleep(50 * time.Millisecond)
+		handledCount.Add(int32(len(items)))
+		// make each work have different duration, and check the active worker number periodically
+		var activeNums []int
+		for i := 0; i < 5-items[0]%2; i++ {
+			time.Sleep(workerIdleDuration * 2)
+			activeNums = append(activeNums, q.GetWorkerActiveNumber())
+		}
+		// When the queue never becomes empty, the existing workers should keep working
+		// It is not 100% true at the moment because the data-race in workergroup.go is not resolved, see that TODO */
+		// If the "active worker numbers" is like [2 2 ... 1 1], it means that an existing worker exited and the no new worker is started.
+		if slices.Equal([]int{1, 1}, activeNums[len(activeNums)-2:]) {
+			hasOnlyOneWorkerRunning.Store(true)
+		}
 		return nil
 	}
-
-	q, _ := newWorkerPoolQueueForTest("test-workpoolqueue", setting.QueueSettings{Type: "channel", BatchLength: 1, MaxWorkers: 2, Length: 100}, handler, false)
+	q, _ = newWorkerPoolQueueForTest("test-workpoolqueue", setting.QueueSettings{Type: "channel", BatchLength: 1, MaxWorkers: 2, Length: 100}, handler, false)
 	stop := runWorkerPoolQueue(q)
-	for i := 0; i < 20; i++ {
+	for i := 0; i < 100; i++ {
 		assert.NoError(t, q.Push(i))
 	}
-
 	time.Sleep(500 * time.Millisecond)
-	assert.EqualValues(t, 2, q.GetWorkerNumber())
-	assert.EqualValues(t, 2, q.GetWorkerActiveNumber())
-	// when the queue never becomes empty, the existing workers should keep working
-	assert.EqualValues(t, 2, q.workerStartedCounter)
+	assert.Greater(t, int(handledCount.Load()), 4) // make sure there are enough items handled during the test
+	assert.False(t, hasOnlyOneWorkerRunning.Load(), "a slow handler should not block other workers from starting")
 	stop()
 }