From 198f690667382420ca5bf44a53f7a30070b0433c Mon Sep 17 00:00:00 2001
From: "Grot (@grafanabot)" <43478413+grafanabot@users.noreply.github.com>
Date: Tue, 19 Jul 2022 06:30:37 +0000
Subject: [PATCH] loki: better handle an empty-response (#52397) (#52431)
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(cherry picked from commit 46eec85b1a0e15c68540fab9fd746a890b8a41a1)

Co-authored-by: Gábor Farkas <gabor.farkas@gmail.com>
---
 pkg/tsdb/loki/api.go                      | 8 ++++++++
 pkg/tsdb/loki/framing_test.go             | 2 ++
 pkg/tsdb/loki/testdata/empty.golden.jsonc | 5 +++++
 pkg/tsdb/loki/testdata/empty.json         | 1 +
 4 files changed, 16 insertions(+)
 create mode 100644 pkg/tsdb/loki/testdata/empty.golden.jsonc
 create mode 100644 pkg/tsdb/loki/testdata/empty.json

diff --git a/pkg/tsdb/loki/api.go b/pkg/tsdb/loki/api.go
index 79501b11146..5ad4402e915 100644
--- a/pkg/tsdb/loki/api.go
+++ b/pkg/tsdb/loki/api.go
@@ -163,6 +163,14 @@ func (api *LokiAPI) DataQuery(ctx context.Context, query lokiQuery) (data.Frames
 	iter := jsoniter.Parse(jsoniter.ConfigDefault, resp.Body, 1024)
 	res := converter.ReadPrometheusStyleResult(iter, converter.Options{MatrixWideSeries: false, VectorWideSeries: false})
 
+	if res == nil {
+		// it's hard to say if this is an error-case or not.
+		// we know the http-response was a success-response
+		// (otherwise we wouldn't be here in the code),
+		// so we will go with a success, with no data.
+		return data.Frames{}, nil
+	}
+
 	if res.Error != nil {
 		return nil, res.Error
 	}
diff --git a/pkg/tsdb/loki/framing_test.go b/pkg/tsdb/loki/framing_test.go
index bb2b3bf16a7..cd057d375d5 100644
--- a/pkg/tsdb/loki/framing_test.go
+++ b/pkg/tsdb/loki/framing_test.go
@@ -48,6 +48,8 @@ func TestSuccessResponse(t *testing.T) {
 		{name: "parse a simple streams response", filepath: "streams_simple", query: streamsQuery},
 
 		{name: "parse a streams response with parse errors", filepath: "streams_parse_errors", query: streamsQuery},
+
+		{name: "parse an empty response", filepath: "empty", query: matrixQuery},
 	}
 
 	for _, test := range tt {
diff --git a/pkg/tsdb/loki/testdata/empty.golden.jsonc b/pkg/tsdb/loki/testdata/empty.golden.jsonc
new file mode 100644
index 00000000000..8850a3f1b08
--- /dev/null
+++ b/pkg/tsdb/loki/testdata/empty.golden.jsonc
@@ -0,0 +1,5 @@
+//  🌟 This was machine generated.  Do not edit. 🌟
+//  🌟 This was machine generated.  Do not edit. 🌟
+{
+  "frames": []
+}
\ No newline at end of file
diff --git a/pkg/tsdb/loki/testdata/empty.json b/pkg/tsdb/loki/testdata/empty.json
new file mode 100644
index 00000000000..9e26dfeeb6e
--- /dev/null
+++ b/pkg/tsdb/loki/testdata/empty.json
@@ -0,0 +1 @@
+{}
\ No newline at end of file