store/prometheus: ensure sidecar respects ext labels (#6564)

Bring back behaviour from pre-0.31.0:
https://github.com/thanos-io/thanos/pull/6127/files#diff-fe654aedc6e5df2ed2a3c493dbb5648358a65ba7c8b3c3029ea099d930b4f00aL333.

Signed-off-by: Giedrius Statkevičius <giedrius.statkevicius@vinted.com>

pkg/store/prometheus.go

@@ -242,13 +242,13 @@ func (p *PrometheusStore) Series(r *storepb.SeriesRequest, s storepb.Store_Serie
 	// remote read.
 	contentType := httpResp.Header.Get("Content-Type")
 	if strings.HasPrefix(contentType, "application/x-protobuf") {
-		return p.handleSampledPrometheusResponse(s, httpResp, queryPrometheusSpan, enableChunkHashCalculation, extLsetToRemove)
+		return p.handleSampledPrometheusResponse(s, httpResp, queryPrometheusSpan, extLset, enableChunkHashCalculation, extLsetToRemove)
 	}
 
 	if !strings.HasPrefix(contentType, "application/x-streamed-protobuf; proto=prometheus.ChunkedReadResponse") {
 		return errors.Errorf("not supported remote read content type: %s", contentType)
 	}
-	return p.handleStreamedPrometheusResponse(s, shardMatcher, httpResp, queryPrometheusSpan, enableChunkHashCalculation, extLsetToRemove)
+	return p.handleStreamedPrometheusResponse(s, shardMatcher, httpResp, queryPrometheusSpan, extLset, enableChunkHashCalculation, extLsetToRemove)
 }
 
 func (p *PrometheusStore) queryPrometheus(
@@ -326,6 +326,7 @@ func (p *PrometheusStore) handleSampledPrometheusResponse(
 	s storepb.Store_SeriesServer,
 	httpResp *http.Response,
 	querySpan tracing.Span,
+	extLset labels.Labels,
 	calculateChecksums bool,
 	extLsetToRemove map[string]struct{},
 ) error {
@@ -342,9 +343,10 @@ func (p *PrometheusStore) handleSampledPrometheusResponse(
 	span.SetTag("series_count", len(resp.Results[0].Timeseries))
 
 	for _, e := range resp.Results[0].Timeseries {
-		// Sampled remote read handler already adds external labels for us:
-		// https://github.com/prometheus/prometheus/blob/3f6f5d3357e232abe53f1775f893fdf8f842712c/storage/remote/read_handler.go#L166.
-		lset := rmLabels(labelpb.ZLabelsToPromLabels(e.Labels), extLsetToRemove)
+		// https://github.com/prometheus/prometheus/blob/3f6f5d3357e232abe53f1775f893fdf8f842712c/storage/remote/read_handler.go#L166
+		// MergeLabels() prefers local labels over external labels but we prefer
+		// external labels hence we need to do this:
+		lset := rmLabels(labelpb.ExtendSortedLabels(labelpb.ZLabelsToPromLabels(e.Labels), extLset), extLsetToRemove)
 		if len(e.Samples) == 0 {
 			// As found in https://github.com/thanos-io/thanos/issues/381
 			// Prometheus can give us completely empty time series. Ignore these with log until we figure out that
@@ -379,6 +381,7 @@ func (p *PrometheusStore) handleStreamedPrometheusResponse(
 	shardMatcher *storepb.ShardMatcher,
 	httpResp *http.Response,
 	querySpan tracing.Span,
+	extLset labels.Labels,
 	calculateChecksums bool,
 	extLsetToRemove map[string]struct{},
 ) error {
@@ -419,10 +422,10 @@ func (p *PrometheusStore) handleStreamedPrometheusResponse(
 
 		framesNum++
 		for _, series := range res.ChunkedSeries {
-			// Streamed remote read handler already adds
-			// external labels:
+			// MergeLabels() prefers local labels over external labels but we prefer
+			// external labels hence we need to do this:
 			// https://github.com/prometheus/prometheus/blob/3f6f5d3357e232abe53f1775f893fdf8f842712c/storage/remote/codec.go#L210.
-			completeLabelset := rmLabels(labelpb.ZLabelsToPromLabels(series.Labels), extLsetToRemove)
+			completeLabelset := rmLabels(labelpb.ExtendSortedLabels(labelpb.ZLabelsToPromLabels(series.Labels), extLset), extLsetToRemove)
 			if !shardMatcher.MatchesLabels(completeLabelset) {
 				continue
 			}

test/e2e/query_test.go

@@ -2241,3 +2241,53 @@ func TestConnectedQueriesWithLazyProxy(t *testing.T) {
 	}, time.Now, promclient.QueryOptions{}, 0)
 
 }
+
+func TestSidecarPrefersExtLabels(t *testing.T) {
+	t.Parallel()
+
+	e, err := e2e.NewDockerEnvironment("sidecar-extlbls")
+	testutil.Ok(t, err)
+	t.Cleanup(e2ethanos.CleanScenario(t, e))
+
+	promCfg := `global:
+  external_labels:
+    region: test`
+
+	prom, sidecar := e2ethanos.NewPrometheusWithSidecar(e, "p1", promCfg, "", e2ethanos.DefaultPrometheusImage(), "", "remote-write-receiver")
+	testutil.Ok(t, e2e.StartAndWaitReady(prom, sidecar))
+
+	endpoints := []string{
+		sidecar.InternalEndpoint("grpc"),
+	}
+	querier := e2ethanos.
+		NewQuerierBuilder(e, "1", endpoints...).
+		Init()
+	testutil.Ok(t, e2e.StartAndWaitReady(querier))
+
+	now := time.Now()
+	ctx := context.Background()
+	m := model.Sample{
+		Metric: map[model.LabelName]model.LabelValue{
+			"__name__": "sidecar_test_metric",
+			"instance": model.LabelValue("test"),
+			"region":   model.LabelValue("foo"),
+		},
+		Value:     model.SampleValue(2),
+		Timestamp: model.TimeFromUnixNano(now.Add(time.Hour).UnixNano()),
+	}
+	testutil.Ok(t, synthesizeSamples(ctx, prom, []model.Sample{m}))
+
+	retv, _ := instantQuery(t, context.Background(), querier.Endpoint("http"), func() string {
+		return "sidecar_test_metric"
+	}, func() time.Time { return now.Add(time.Hour) }, promclient.QueryOptions{}, 1)
+
+	testutil.Equals(t, model.Vector{&model.Sample{
+		Metric: model.Metric{
+			"__name__": "sidecar_test_metric",
+			"instance": "test",
+			"region":   "test",
+		},
+		Value:     model.SampleValue(2),
+		Timestamp: model.TimeFromUnixNano(now.Add(time.Hour).UnixNano()),
+	}}, retv)
+}