From 3cc28aaf0ec08373fb104327827e6a062807e7ff Mon Sep 17 00:00:00 2001
From: Shantanu Alshi <shantanu.alshi@grafana.com>
Date: Mon, 13 May 2024 15:56:08 +0530
Subject: [PATCH] fix: panics when ingester response is nil (#12946)

---
 pkg/querier/ingester_querier.go |  4 ++++
 pkg/querier/querier.go          | 12 ++++++------
 pkg/querier/querier_test.go     | 27 +++++++++++++++++++++++++++
 3 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/pkg/querier/ingester_querier.go b/pkg/querier/ingester_querier.go
index e99fe6882df4..c18ca7793066 100644
--- a/pkg/querier/ingester_querier.go
+++ b/pkg/querier/ingester_querier.go
@@ -380,6 +380,10 @@ func (q *IngesterQuerier) DetectedLabel(ctx context.Context, req *logproto.Detec
 				"response", resp)
 		}
 
+		if thisIngester == nil {
+			continue
+		}
+
 		for label, thisIngesterValues := range thisIngester.Labels {
 			var combinedValues []string
 			allIngesterValues, isLabelPresent := labelMap[label]
diff --git a/pkg/querier/querier.go b/pkg/querier/querier.go
index 12429e68a3e0..bafbe334cdf7 100644
--- a/pkg/querier/querier.go
+++ b/pkg/querier/querier.go
@@ -985,14 +985,14 @@ func (q *SingleTenantQuerier) DetectedLabels(ctx context.Context, req *logproto.
 		}, nil
 	}
 
-	// append static labels before so they are in sorted order
-	for l := range staticLabels {
-		if values, present := ingesterLabels.Labels[l]; present {
-			detectedLabels = append(detectedLabels, &logproto.DetectedLabel{Label: l, Cardinality: uint64(len(values.Values))})
+	if ingesterLabels != nil {
+		// append static labels before so they are in sorted order
+		for l := range staticLabels {
+			if values, present := ingesterLabels.Labels[l]; present {
+				detectedLabels = append(detectedLabels, &logproto.DetectedLabel{Label: l, Cardinality: uint64(len(values.Values))})
+			}
 		}
-	}
 
-	if ingesterLabels != nil {
 		for label, values := range ingesterLabels.Labels {
 			if q.isLabelRelevant(label, values.Values, staticLabels) {
 				combinedValues := values.Values
diff --git a/pkg/querier/querier_test.go b/pkg/querier/querier_test.go
index 2dfd3d897431..66370c34460b 100644
--- a/pkg/querier/querier_test.go
+++ b/pkg/querier/querier_test.go
@@ -1714,4 +1714,31 @@ func TestQuerier_DetectedLabels(t *testing.T) {
 		assert.Contains(t, detectedLabels, &logproto.DetectedLabel{Label: "pod", Cardinality: 4})
 		assert.Contains(t, detectedLabels, &logproto.DetectedLabel{Label: "namespace", Cardinality: 60})
 	})
+
+	t.Run("no panics with ingester response is nil", func(t *testing.T) {
+		ingesterClient := newQuerierClientMock()
+		storeClient := newStoreMock()
+
+		ingesterClient.On("GetDetectedLabels", mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything).
+			Return(nil, nil)
+		storeClient.On("LabelNamesForMetricName", mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything).
+			Return([]string{}, nil)
+		request := logproto.DetectedLabelsRequest{
+			Start: &now,
+			End:   &now,
+			Query: "",
+		}
+
+		querier, err := newQuerier(
+			conf,
+			mockIngesterClientConfig(),
+			newIngesterClientMockFactory(ingesterClient),
+			mockReadRingWithOneActiveIngester(),
+			&mockDeleteGettter{},
+			storeClient, limits)
+		require.NoError(t, err)
+
+		_, err = querier.DetectedLabels(ctx, &request)
+		require.NoError(t, err)
+	})
 }