[store] Add Request Hints for Labels APIs (#3469)

Signed-off-by: Goutham Veeramachaneni <gouthamve@gmail.com>

CHANGELOG.md

@@ -31,6 +31,7 @@ We use _breaking :warning:_ to mark changes that are not backward compatible (re
 - [#3431](https://github.com/thanos-io/thanos/pull/3431) Store: Added experimental support to lazy load index-headers at query time. When enabled via `--store.enable-index-header-lazy-reader` flag, the store-gateway will load into memory an index-header only once it's required at query time. Index-header will be automatically released after `--store.index-header-lazy-reader-idle-timeout` of inactivity.
   - This, generally, reduces baseline memory usage of store when inactive, as well as a total number of mapped files (which is limited to 64k in some systems.
 - [#3437](https://github.com/thanos-io/thanos/pull/3437) StoreAPI: Added `hints` field to `LabelNamesResponse` and `LabelValuesResponse`. Hints in an opaque data structure that can be used to carry additional information from the store and its content is implementation specific.
+- [#3469](https://github.com/thanos-io/thanos/pull/3469) StoreAPI: Added `hints` field to `LabelNamesRequest` and `LabelValuesRequest`. Hints in an opaque data structure that can be used to carry additional information from the store and its content is implementation specific.
 
 ### Fixed
 

pkg/store/bucket.go

@@ -1074,11 +1074,28 @@ func (s *BucketStore) LabelNames(ctx context.Context, req *storepb.LabelNamesReq
 
 	var mtx sync.Mutex
 	var sets [][]string
+	var reqBlockMatchers []*labels.Matcher
+
+	if req.Hints != nil {
+		reqHints := &hintspb.LabelNamesRequestHints{}
+		err := types.UnmarshalAny(req.Hints, reqHints)
+		if err != nil {
+			return nil, status.Error(codes.InvalidArgument, errors.Wrap(err, "unmarshal label names request hints").Error())
+		}
+
+		reqBlockMatchers, err = storepb.TranslateFromPromMatchers(reqHints.BlockMatchers...)
+		if err != nil {
+			return nil, status.Error(codes.InvalidArgument, errors.Wrap(err, "translate request hints labels matchers").Error())
+		}
+	}
 
 	for _, b := range s.blocks {
 		if !b.overlapsClosedInterval(req.Start, req.End) {
 			continue
 		}
+		if len(reqBlockMatchers) > 0 && !b.matchRelabelLabels(reqBlockMatchers) {
+			continue
+		}
 
 		resHints.AddQueriedBlock(b.meta.ULID)
 
@@ -1141,11 +1158,28 @@ func (s *BucketStore) LabelValues(ctx context.Context, req *storepb.LabelValuesR
 
 	var mtx sync.Mutex
 	var sets [][]string
+	var reqBlockMatchers []*labels.Matcher
+
+	if req.Hints != nil {
+		reqHints := &hintspb.LabelValuesRequestHints{}
+		err := types.UnmarshalAny(req.Hints, reqHints)
+		if err != nil {
+			return nil, status.Error(codes.InvalidArgument, errors.Wrap(err, "unmarshal label names request hints").Error())
+		}
+
+		reqBlockMatchers, err = storepb.TranslateFromPromMatchers(reqHints.BlockMatchers...)
+		if err != nil {
+			return nil, status.Error(codes.InvalidArgument, errors.Wrap(err, "translate request hints labels matchers").Error())
+		}
+	}
 
 	for _, b := range s.blocks {
 		if !b.overlapsClosedInterval(req.Start, req.End) {
 			continue
 		}
+		if len(reqBlockMatchers) > 0 && !b.matchRelabelLabels(reqBlockMatchers) {
+			continue
+		}
 
 		resHints.AddQueriedBlock(b.meta.ULID)
 

pkg/store/bucket_test.go

@@ -2136,6 +2136,41 @@ func TestLabelNamesAndValuesHints(t *testing.T) {
 					{Id: block2.String()},
 				},
 			},
+		}, {
+			name: "querying a range containing multiple blocks but filtering a specific block should query only the requested block",
+
+			labelNamesReq: &storepb.LabelNamesRequest{
+				Start: 0,
+				End:   3,
+				Hints: mustMarshalAny(&hintspb.LabelNamesRequestHints{
+					BlockMatchers: []storepb.LabelMatcher{
+						{Type: storepb.LabelMatcher_EQ, Name: block.BlockIDLabel, Value: block1.String()},
+					},
+				}),
+			},
+			expectedNames: labelNamesFromSeriesSet(seriesSet1),
+			expectedNamesHints: hintspb.LabelNamesResponseHints{
+				QueriedBlocks: []hintspb.Block{
+					{Id: block1.String()},
+				},
+			},
+
+			labelValuesReq: &storepb.LabelValuesRequest{
+				Label: "ext1",
+				Start: 0,
+				End:   3,
+				Hints: mustMarshalAny(&hintspb.LabelValuesRequestHints{
+					BlockMatchers: []storepb.LabelMatcher{
+						{Type: storepb.LabelMatcher_EQ, Name: block.BlockIDLabel, Value: block1.String()},
+					},
+				}),
+			},
+			expectedValues: []string{"1"},
+			expectedValuesHints: hintspb.LabelValuesResponseHints{
+				QueriedBlocks: []hintspb.Block{
+					{Id: block1.String()},
+				},
+			},
 		},
 	}