Sync test from pr14831

Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com>

tsdb/head.go

@@ -128,6 +128,7 @@ type Head struct {
 	writeNotified wlog.WriteNotified
 
 	memTruncationInProcess atomic.Bool
+	memTruncationCallBack func()
 }
 
 type ExemplarStorage interface {
@@ -1147,6 +1148,10 @@ func (h *Head) truncateMemory(mint int64) (err error) {
 	h.memTruncationInProcess.Store(true)
 	defer h.memTruncationInProcess.Store(false)
 
+	if h.memTruncationCallBack != nil {
+		h.memTruncationCallBack()
+	}
+
 	// We wait for pending queries to end that overlap with this truncation.
 	if initialized {
 		h.WaitForPendingReadersInTimeRange(h.MinTime(), mint)

tsdb/head_test.go

@@ -3506,12 +3506,13 @@ func TestWaitForPendingReadersInTimeRange(t *testing.T) {
 }
 
 func TestQueryOOOHeadDuringTruncate(t *testing.T) {
-	const maxT int64 = 4000
+	const maxT int64 = 6000
 
 	dir := t.TempDir()
 	opts := DefaultOptions()
 	opts.EnableNativeHistograms = true
 	opts.OutOfOrderTimeWindow = maxT
+	opts.MinBlockDuration = maxT / 2 // So that head will compact up to 3000.
 
 	db, err := Open(dir, nil, nil, opts, nil)
 	require.NoError(t, err)
@@ -3538,49 +3539,57 @@ func TestQueryOOOHeadDuringTruncate(t *testing.T) {
 
 	requireEqualOOOSamples(t, int(maxT/100-1), db)
 
-	// This mocks truncation.
+	// Synchronization points.
-	db.head.memTruncationInProcess.Store(true)
+	allowQueryToStart := make(chan struct{})
-	db.head.lastMemoryTruncationTime.Store(3000)
+	queryStarted := make(chan struct{})
+	compactionFinished := make(chan struct{})
+
+	db.head.memTruncationCallBack = func() {
+		// Compaction has started, let the query start and wait for it to actually start to simulate race condition.
+		allowQueryToStart <- struct{}{}
+		<-queryStarted
+	}
+
+	go func() {
+		db.Compact(context.Background()) // Compact and write blocks up to 3000 (maxtT/2).
+		compactionFinished <- struct{}{}
+	}()
+
+	// Wait for the compaction to start.
+	<-allowQueryToStart
 
-	t.Run("LabelNames", func(t *testing.T) {
-		// Query the head and overlap with the truncation time.
 	q, err := db.Querier(1500, 2500)
 	require.NoError(t, err)
+	queryStarted <- struct{}{} // Unblock the compaction.
 	ctx := context.Background()
+
+	// Label names.
 	res, annots, err := q.LabelNames(ctx, nil, labels.MustNewMatcher(labels.MatchEqual, "a", "b"))
 	require.NoError(t, err)
 	require.Empty(t, annots)
 	require.Equal(t, []string{"a"}, res)
-		require.NoError(t, q.Close())
-	})
 
-	t.Run("LabelValues", func(t *testing.T) {
+	// Label values.
-		// Query the head and overlap with the truncation time.
+	res, annots, err = q.LabelValues(ctx, "a", nil, labels.MustNewMatcher(labels.MatchEqual, "a", "b"))
-		q, err := db.Querier(1500, 2500)
-		require.NoError(t, err)
-		ctx := context.Background()
-		res, annots, err := q.LabelValues(ctx, "a", nil, labels.MustNewMatcher(labels.MatchEqual, "a", "b"))
 	require.NoError(t, err)
 	require.Empty(t, annots)
 	require.Equal(t, []string{"b"}, res)
-		require.NoError(t, q.Close())
-	})
 
-	t.Run("Select", func(t *testing.T) {
+	// Samples
-		// Query the head and overlap with the truncation time.
-		q, err := db.Querier(1500, 2500)
-		require.NoError(t, err)
-		ctx := context.Background()
 	ss := q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchEqual, "a", "b"))
 	require.True(t, ss.Next())
 	s := ss.At()
 	require.False(t, ss.Next()) // One series.
 	it := s.Iterator(nil)
 	require.NotEqual(t, chunkenc.ValNone, it.Next()) // Has some data.
-		require.Equal(t, int64(1550), it.AtT())          // It's from OOO head.
+	require.Equal(t, int64(1500), it.AtT())          // It is an in-order sample.
+	require.NotEqual(t, chunkenc.ValNone, it.Next()) // Has some data.
+	require.Equal(t, int64(1550), it.AtT())          // it is an out-of-order sample.
 	require.NoError(t, it.Err())
-		require.NoError(t, q.Close())
+
-	})
+	require.NoError(t, q.Close()) // Cannot be deferred as the compaction waits for queries to close before finishing.
+
+	<-compactionFinished // Wait for compaction otherwise Go test finds stray goroutines.
 }
 
 func TestAppendHistogram(t *testing.T) {