loki: fix bug in labels framing (#51015)

pkg/util/converter/prom.go

@@ -695,6 +695,9 @@ func readStream(iter *jsoniter.Iterator) *backend.DataResponse {
 		for l1Field := iter.ReadObject(); l1Field != ""; l1Field = iter.ReadObject() {
 			switch l1Field {
 			case "stream":
+				// we need to clear `labels`, because `iter.ReadVal`
+				// only appends to it
+				labels := data.Labels{}
 				iter.ReadVal(&labels)
 				labelJson, err = labelsToRawJson(labels)
 				if err != nil {

pkg/util/converter/prom_test.go

@@ -32,6 +32,7 @@ func TestReadPromFrames(t *testing.T) {
 		"prom-exemplars",
 		"loki-streams-a",
 		"loki-streams-b",
+		"loki-streams-c",
 	}
 
 	for _, name := range files {

pkg/util/converter/testdata/loki-streams-c-frame.jsonc

@@ -0,0 +1,79 @@
+//  🌟 This was machine generated.  Do not edit. 🌟
+//  
+//  Frame[0] {}
+//  Name: 
+//  Dimensions: 4 Fields by 2 Rows
+//  +-------------------------+-------------------------------+----------------+---------------------+
+//  | Name: __labels          | Name: Time                    | Name: Line     | Name: TS            |
+//  | Labels:                 | Labels:                       | Labels:        | Labels:             |
+//  | Type: []json.RawMessage | Type: []time.Time             | Type: []string | Type: []string      |
+//  +-------------------------+-------------------------------+----------------+---------------------+
+//  | {"label1":"value1"}     | 2022-06-17 06:49:51 +0000 UTC | text1          | 1655448591000000000 |
+//  | {"label2":"value2"}     | 2022-06-17 06:49:52 +0000 UTC | text2          | 1655448592000000000 |
+//  +-------------------------+-------------------------------+----------------+---------------------+
+//  
+//  
+//  🌟 This was machine generated.  Do not edit. 🌟
+{
+  "frames": [
+    {
+      "schema": {
+        "meta": {},
+        "fields": [
+          {
+            "name": "__labels",
+            "type": "other",
+            "typeInfo": {
+              "frame": "json.RawMessage"
+            }
+          },
+          {
+            "name": "Time",
+            "type": "time",
+            "typeInfo": {
+              "frame": "time.Time"
+            }
+          },
+          {
+            "name": "Line",
+            "type": "string",
+            "typeInfo": {
+              "frame": "string"
+            }
+          },
+          {
+            "name": "TS",
+            "type": "string",
+            "typeInfo": {
+              "frame": "string"
+            }
+          }
+        ]
+      },
+      "data": {
+        "values": [
+          [
+            {
+              "label1": "value1"
+            },
+            {
+              "label2": "value2"
+            }
+          ],
+          [
+            1655448591000,
+            1655448592000
+          ],
+          [
+            "text1",
+            "text2"
+          ],
+          [
+            "1655448591000000000",
+            "1655448592000000000"
+          ]
+        ]
+      }
+    }
+  ]
+}

pkg/util/converter/testdata/loki-streams-c-wide-frame.jsonc

@@ -0,0 +1,79 @@
+//  🌟 This was machine generated.  Do not edit. 🌟
+//  
+//  Frame[0] {}
+//  Name: 
+//  Dimensions: 4 Fields by 2 Rows
+//  +-------------------------+-------------------------------+----------------+---------------------+
+//  | Name: __labels          | Name: Time                    | Name: Line     | Name: TS            |
+//  | Labels:                 | Labels:                       | Labels:        | Labels:             |
+//  | Type: []json.RawMessage | Type: []time.Time             | Type: []string | Type: []string      |
+//  +-------------------------+-------------------------------+----------------+---------------------+
+//  | {"label1":"value1"}     | 2022-06-17 06:49:51 +0000 UTC | text1          | 1655448591000000000 |
+//  | {"label2":"value2"}     | 2022-06-17 06:49:52 +0000 UTC | text2          | 1655448592000000000 |
+//  +-------------------------+-------------------------------+----------------+---------------------+
+//  
+//  
+//  🌟 This was machine generated.  Do not edit. 🌟
+{
+  "frames": [
+    {
+      "schema": {
+        "meta": {},
+        "fields": [
+          {
+            "name": "__labels",
+            "type": "other",
+            "typeInfo": {
+              "frame": "json.RawMessage"
+            }
+          },
+          {
+            "name": "Time",
+            "type": "time",
+            "typeInfo": {
+              "frame": "time.Time"
+            }
+          },
+          {
+            "name": "Line",
+            "type": "string",
+            "typeInfo": {
+              "frame": "string"
+            }
+          },
+          {
+            "name": "TS",
+            "type": "string",
+            "typeInfo": {
+              "frame": "string"
+            }
+          }
+        ]
+      },
+      "data": {
+        "values": [
+          [
+            {
+              "label1": "value1"
+            },
+            {
+              "label2": "value2"
+            }
+          ],
+          [
+            1655448591000,
+            1655448592000
+          ],
+          [
+            "text1",
+            "text2"
+          ],
+          [
+            "1655448591000000000",
+            "1655448592000000000"
+          ]
+        ]
+      }
+    }
+  ]
+}

pkg/util/converter/testdata/loki-streams-c.json

@@ -0,0 +1,17 @@
+{
+  "status": "success",
+  "data": {
+    "resultType": "streams",
+    "result": [
+      {
+        "stream": {  "label1": "value1" },
+        "values": [["1655448591000000000", "text1"]
+        ]
+      },
+      {
+        "stream": { "label2": "value2"},
+        "values": [["1655448592000000000", "text2"]]
+      }
+    ]
+  }
+}