Cherry pick changes from #4269, #4303 and #4318 onto main.

This does not include the associated integration test changes, or
changes to tests that have not yet been merged to main.

CHANGELOG.md

@@ -43,7 +43,7 @@ Querying with using `{__mimir_storage__="ephemeral"}` selector no longer works.
 * [ENHANCEMENT] Store-gateway: Reduce memory allocation rate when loading TSDB chunks from Memcached. #4074
 * [ENHANCEMENT] Query-frontend: track `cortex_frontend_query_response_codec_duration_seconds` and `cortex_frontend_query_response_codec_payload_bytes` metrics to measure the time taken and bytes read / written while encoding and decoding query result payloads. #4110
 * [ENHANCEMENT] Alertmanager: expose additional upstream metrics `cortex_alertmanager_dispatcher_aggregation_groups`, `cortex_alertmanager_dispatcher_alert_processing_duration_seconds`. #4151
-* [ENHANCEMENT] Querier and query-frontend: add experimental, more performant protobuf query result response format enabled with `-query-frontend.query-result-response-format=protobuf`. #4153
+* [ENHANCEMENT] Querier and query-frontend: add experimental, more performant protobuf query result response format enabled with `-query-frontend.query-result-response-format=protobuf`. #4153 #4304 #4318
 * [ENHANCEMENT] Store-gateway: use more efficient chunks fetching and caching. This should reduce CPU, memory utilization, and receive bandwidth of a store-gateway. Enable with `-blocks-storage.bucket-store.chunks-cache.fine-grained-chunks-caching-enabled=true`. #4163 #4174 #4227
 * [ENHANCEMENT] Query-frontend: Wait for in-flight queries to finish before shutting down. #4073 #4170
 * [ENHANCEMENT] Store-gateway: added `encode` and `other` stage to `cortex_bucket_store_series_request_stage_duration_seconds` metric. #4179

pkg/frontend/querymiddleware/codec_protobuf.go

@@ -98,7 +98,7 @@ func (f protobufFormat) decodeScalarData(data *mimirpb.ScalarData) *PrometheusDa
 }
 
 func (f protobufFormat) decodeVectorData(data *mimirpb.VectorData) (*PrometheusData, error) {
-	streams := make([]SampleStream, len(data.Samples))
+	streams := make([]SampleStream, len(data.Samples)+len(data.Histograms))
 
 	for i, sample := range data.Samples {
 		l, err := labelsFromStringArray(sample.Metric)
@@ -114,6 +114,23 @@ func (f protobufFormat) decodeVectorData(data *mimirpb.VectorData) (*PrometheusD
 		}
 	}
 
+	for i, sample := range data.Histograms {
+		l, err := labelsFromStringArray(sample.Metric)
+		if err != nil {
+			return nil, err
+		}
+
+		streams[i+len(data.Samples)] = SampleStream{
+			Labels: l,
+			Histograms: []mimirpb.FloatHistogramPair{
+				{
+					TimestampMs: sample.TimestampMs,
+					Histogram:   sample.Histogram,
+				},
+			},
+		}
+	}
+
 	return &PrometheusData{
 		ResultType: model.ValVector.String(),
 		Result:     streams,
@@ -129,18 +146,10 @@ func (f protobufFormat) decodeMatrixData(data *mimirpb.MatrixData) (*PrometheusD
 			return nil, err
 		}
 
-		samples := make([]mimirpb.Sample, len(series.Samples))
-
-		for sampleIdx, sample := range series.Samples {
-			samples[sampleIdx] = mimirpb.Sample{
-				TimestampMs: sample.TimestampMs,
-				Value:       sample.Value,
-			}
-		}
-
 		streams[seriesIdx] = SampleStream{
-			Labels:  l,
-			Samples: samples,
+			Labels:     l,
+			Samples:    series.Samples,
+			Histograms: series.Histograms,
 		}
 	}