Loki: Fix a bug when reading frames without values but warnings (#97197)

* Loki: Fix a bug when reading frames without values but warnings

* Loki: Better bail if fields are less than 2

pkg/tsdb/loki/frame.go

@@ -10,19 +10,10 @@ import (
 	"github.com/grafana/grafana-plugin-sdk-go/data"
 )
 
-// we adjust the dataframes to be the way frontend & alerting
-// wants them.
 func adjustFrame(frame *data.Frame, query *lokiQuery, setMetricFrameName bool, logsDataplane bool) error {
-	fields := frame.Fields
-
-	if len(fields) < 2 {
-		return fmt.Errorf("missing fields in frame")
-	}
-
 	// metric-fields have "timefield, valuefield"
 	// logs-fields have "labelsfield, timefield, ..."
-
-	secondField := fields[1]
+	secondField := frame.Fields[1]
 
 	if secondField.Type() == data.FieldTypeFloat64 {
 		return adjustMetricFrame(frame, query, setMetricFrameName)

pkg/tsdb/loki/framing_test.go

@@ -54,6 +54,8 @@ func TestSuccessResponse(t *testing.T) {
 
 		{name: "parse structured metadata", filepath: "streams_structured_metadata", query: streamsQuery},
 		{name: "parse structured metadata different labels each log line", filepath: "streams_structured_metadata_2", query: streamsQuery},
+
+		{name: "parse warnings", filepath: "warning", query: streamsQuery},
 	}
 
 	runTest := func(folder string, path string, query lokiQuery, responseOpts ResponseOpts) {

pkg/tsdb/loki/loki.go

@@ -289,8 +289,12 @@ func runQuery(ctx context.Context, api *LokiAPI, query *lokiQuery, responseOpts
 	}
 
 	for _, frame := range res.Frames {
-		err = adjustFrame(frame, query, false, responseOpts.logsDataplane)
+		// Skip frames without fields
+		if len(frame.Fields) < 2 {
+			continue
+		}
 
+		err = adjustFrame(frame, query, false, responseOpts.logsDataplane)
 		if err != nil {
 			plog.Error("Error adjusting frame", "error", err)
 			return res, err

pkg/tsdb/loki/test_non_dataplane/warning.golden.jsonc

@@ -0,0 +1,47 @@
+//  🌟 This was machine generated.  Do not edit. 🌟
+//  
+//  Frame[0] {
+//      "typeVersion": [
+//          0,
+//          0
+//      ],
+//      "notices": [
+//          {
+//              "severity": "warning",
+//              "text": "Some logs may have been dropped by Adaptive Logs sampling"
+//          }
+//      ]
+//  }
+//  Name: Warnings
+//  Dimensions: 0 Fields by 0 Rows
+//  +
+//  +
+//  
+//  
+//  🌟 This was machine generated.  Do not edit. 🌟
+{
+  "status": 200,
+  "frames": [
+    {
+      "schema": {
+        "name": "Warnings",
+        "meta": {
+          "typeVersion": [
+            0,
+            0
+          ],
+          "notices": [
+            {
+              "severity": "warning",
+              "text": "Some logs may have been dropped by Adaptive Logs sampling"
+            }
+          ]
+        },
+        "fields": []
+      },
+      "data": {
+        "values": []
+      }
+    }
+  ]
+}

pkg/tsdb/loki/test_non_dataplane/warning.json

@@ -0,0 +1,4 @@
+{
+  "status": "success",
+  "warnings": ["Some logs may have been dropped by Adaptive Logs sampling"]
+}

pkg/tsdb/loki/testdata_dataplane/warning.golden.jsonc

@@ -0,0 +1,47 @@
+//  🌟 This was machine generated.  Do not edit. 🌟
+//  
+//  Frame[0] {
+//      "typeVersion": [
+//          0,
+//          0
+//      ],
+//      "notices": [
+//          {
+//              "severity": "warning",
+//              "text": "Some logs may have been dropped by Adaptive Logs sampling"
+//          }
+//      ]
+//  }
+//  Name: Warnings
+//  Dimensions: 0 Fields by 0 Rows
+//  +
+//  +
+//  
+//  
+//  🌟 This was machine generated.  Do not edit. 🌟
+{
+  "status": 200,
+  "frames": [
+    {
+      "schema": {
+        "name": "Warnings",
+        "meta": {
+          "typeVersion": [
+            0,
+            0
+          ],
+          "notices": [
+            {
+              "severity": "warning",
+              "text": "Some logs may have been dropped by Adaptive Logs sampling"
+            }
+          ]
+        },
+        "fields": []
+      },
+      "data": {
+        "values": []
+      }
+    }
+  ]
+}

pkg/tsdb/loki/testdata_dataplane/warning.json

@@ -0,0 +1,4 @@
+{
+  "status": "success",
+  "warnings": ["Some logs may have been dropped by Adaptive Logs sampling"]
+}