From 6f99af62227f98c7d9de8a5cf480ae792ce6220a Mon Sep 17 00:00:00 2001
From: Shantanu Alshi <shantanu.alshi@grafana.com>
Date: Tue, 27 Aug 2024 17:27:58 +0530
Subject: [PATCH] fix(detected labels): response when store label values are
 empty (#13970)

---
 pkg/querier/querier.go           |  4 ++--
 pkg/querier/querier_mock_test.go |  3 +++
 pkg/querier/querier_test.go      | 34 ++++++++++++++++++++++++++++++++
 3 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/pkg/querier/querier.go b/pkg/querier/querier.go
index ac83218f9331..b320e5c5fd6a 100644
--- a/pkg/querier/querier.go
+++ b/pkg/querier/querier.go
@@ -995,7 +995,7 @@ func countLabelsAndCardinality(storeLabelsMap map[string][]string, ingesterLabel
 
 	if ingesterLabels != nil {
 		for label, val := range ingesterLabels.Labels {
-			if _, isStatic := staticLabels[label]; isStatic || !containsAllIDTypes(val.Values) {
+			if _, isStatic := staticLabels[label]; (isStatic && val.Values != nil) || !containsAllIDTypes(val.Values) {
 				_, ok := dlMap[label]
 				if !ok {
 					dlMap[label] = newParsedLabels()
@@ -1010,7 +1010,7 @@ func countLabelsAndCardinality(storeLabelsMap map[string][]string, ingesterLabel
 	}
 
 	for label, values := range storeLabelsMap {
-		if _, isStatic := staticLabels[label]; isStatic || !containsAllIDTypes(values) {
+		if _, isStatic := staticLabels[label]; (isStatic && values != nil) || !containsAllIDTypes(values) {
 			_, ok := dlMap[label]
 			if !ok {
 				dlMap[label] = newParsedLabels()
diff --git a/pkg/querier/querier_mock_test.go b/pkg/querier/querier_mock_test.go
index e8a3b40ebd61..4ddbab7ed2e5 100644
--- a/pkg/querier/querier_mock_test.go
+++ b/pkg/querier/querier_mock_test.go
@@ -350,6 +350,9 @@ func (s *storeMock) PutOne(_ context.Context, _, _ model.Time, _ chunk.Chunk) er
 
 func (s *storeMock) LabelValuesForMetricName(ctx context.Context, userID string, from, through model.Time, metricName string, labelName string, _ ...*labels.Matcher) ([]string, error) {
 	args := s.Called(ctx, userID, from, through, metricName, labelName)
+	if args.Get(0) == nil {
+		return nil, args.Error(1)
+	}
 	return args.Get(0).([]string), args.Error(1)
 }
 
diff --git a/pkg/querier/querier_test.go b/pkg/querier/querier_test.go
index 9e98a780561f..7336c3b11bfa 100644
--- a/pkg/querier/querier_test.go
+++ b/pkg/querier/querier_test.go
@@ -1518,6 +1518,40 @@ func TestQuerier_DetectedLabels(t *testing.T) {
 		}
 	})
 
+	t.Run("label is not present when the values are nil", func(t *testing.T) {
+		ingesterClient := newQuerierClientMock()
+		storeClient := newStoreMock()
+
+		ingesterClient.On("GetDetectedLabels", mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything).
+			Return(&logproto.LabelToValuesResponse{}, nil)
+		storeClient.On("LabelNamesForMetricName", mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything).
+			Return([]string{"storeLabel1", "pod"}, nil).
+			On("LabelValuesForMetricName", mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything, "storeLabel1", mock.Anything).
+			Return([]string{"val1", "val2"}, nil).
+			On("LabelValuesForMetricName", mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything, "pod", mock.Anything).
+			Return(nil, nil)
+
+		querier, err := newQuerier(
+			conf,
+			mockIngesterClientConfig(),
+			newIngesterClientMockFactory(ingesterClient),
+			mockReadRingWithOneActiveIngester(),
+			&mockDeleteGettter{},
+			storeClient, limits)
+		require.NoError(t, err)
+
+		resp, err := querier.DetectedLabels(ctx, &request)
+		require.NoError(t, err)
+
+		detectedLabels := resp.DetectedLabels
+		assert.Len(t, detectedLabels, 1)
+		expectedCardinality := map[string]uint64{"storeLabel1": 2}
+		for _, d := range detectedLabels {
+			card := expectedCardinality[d.Label]
+			assert.Equal(t, d.Cardinality, card, "Expected cardinality mismatch for: ", d.Label)
+		}
+	})
+
 	t.Run("returns a response when store data is empty", func(t *testing.T) {
 		ingesterResponse := logproto.LabelToValuesResponse{Labels: map[string]*logproto.UniqueLabelValues{
 			"cluster":       {Values: []string{"ingester"}},