Improve streaming on MetricsForLabelMatchersStream method

pkg/ingester/ingester.go

@@ -1696,27 +1696,42 @@ func (i *Ingester) labelNamesCommon(ctx context.Context, req *client.LabelNamesR
 
 // MetricsForLabelMatchers returns all the metrics which match a set of matchers.
 func (i *Ingester) MetricsForLabelMatchers(ctx context.Context, req *client.MetricsForLabelMatchersRequest) (*client.MetricsForLabelMatchersResponse, error) {
-	result, cleanup, err := i.metricsForLabelMatchersCommon(ctx, req)
+	result := &client.MetricsForLabelMatchersResponse{}
+	cleanup, err := i.metricsForLabelMatchersCommon(ctx, req, func(l labels.Labels) error {
+		result.Metric = append(result.Metric, &cortexpb.Metric{
+			Labels: cortexpb.FromLabelsToLabelAdapters(l),
+		})
+		return nil
+	})
 	defer cleanup()
 	return result, err
 }
 
 func (i *Ingester) MetricsForLabelMatchersStream(req *client.MetricsForLabelMatchersRequest, stream client.Ingester_MetricsForLabelMatchersStreamServer) error {
-	result, cleanup, err := i.metricsForLabelMatchersCommon(stream.Context(), req)
+	result := &client.MetricsForLabelMatchersStreamResponse{}
+
+	cleanup, err := i.metricsForLabelMatchersCommon(stream.Context(), req, func(l labels.Labels) error {
+		result.Metric = append(result.Metric, &cortexpb.Metric{
+			Labels: cortexpb.FromLabelsToLabelAdapters(l),
+		})
+
+		if len(result.Metric) >= metadataStreamBatchSize {
+			err := client.SendMetricsForLabelMatchersStream(stream, result)
+			if err != nil {
+				return err
+			}
+			result.Metric = result.Metric[:0]
+		}
+		return nil
+	})
 	defer cleanup()
 	if err != nil {
 		return err
 	}
 
-	for i := 0; i < len(result.Metric); i += metadataStreamBatchSize {
-		j := i + metadataStreamBatchSize
-		if j > len(result.Metric) {
-			j = len(result.Metric)
-		}
-		resp := &client.MetricsForLabelMatchersStreamResponse{
-			Metric: result.Metric[i:j],
-		}
-		err := client.SendMetricsForLabelMatchersStream(stream, resp)
+	// Send last batch
+	if len(result.Metric) > 0 {
+		err := client.SendMetricsForLabelMatchersStream(stream, result)
 		if err != nil {
 			return err
 		}
@@ -1728,36 +1743,36 @@ func (i *Ingester) MetricsForLabelMatchersStream(req *client.MetricsForLabelMatc
 // metricsForLabelMatchersCommon returns all the metrics which match a set of matchers.
 // this should be used by MetricsForLabelMatchers and MetricsForLabelMatchersStream.
 // the cleanup function should be called in order to close the querier
-func (i *Ingester) metricsForLabelMatchersCommon(ctx context.Context, req *client.MetricsForLabelMatchersRequest) (*client.MetricsForLabelMatchersResponse, func(), error) {
+func (i *Ingester) metricsForLabelMatchersCommon(ctx context.Context, req *client.MetricsForLabelMatchersRequest, acc func(labels.Labels) error) (func(), error) {
 	cleanup := func() {}
 	if err := i.checkRunning(); err != nil {
-		return nil, cleanup, err
+		return cleanup, err
 	}
 
 	userID, err := tenant.TenantID(ctx)
 	if err != nil {
-		return nil, cleanup, err
+		return cleanup, err
 	}
 
 	db := i.getTSDB(userID)
 	if db == nil {
-		return &client.MetricsForLabelMatchersResponse{}, cleanup, nil
+		return cleanup, nil
 	}
 
 	// Parse the request
 	_, _, limit, matchersSet, err := client.FromMetricsForLabelMatchersRequest(req)
 	if err != nil {
-		return nil, cleanup, err
+		return cleanup, err
 	}
 
 	mint, maxt, err := metadataQueryRange(req.StartTimestampMs, req.EndTimestampMs, db, i.cfg.QueryIngestersWithin)
 	if err != nil {
-		return nil, cleanup, err
+		return cleanup, err
 	}
 
 	q, err := db.Querier(mint, maxt)
 	if err != nil {
-		return nil, cleanup, err
+		return cleanup, err
 	}
 
 	cleanup = func() {
@@ -1780,7 +1795,7 @@ func (i *Ingester) metricsForLabelMatchersCommon(ctx context.Context, req *clien
 		for _, matchers := range matchersSet {
 			// Interrupt if the context has been canceled.
 			if ctx.Err() != nil {
-				return nil, cleanup, ctx.Err()
+				return cleanup, ctx.Err()
 			}
 
 			seriesSet := q.Select(ctx, true, hints, matchers...)
@@ -1791,28 +1806,23 @@ func (i *Ingester) metricsForLabelMatchersCommon(ctx context.Context, req *clien
 		mergedSet = q.Select(ctx, false, hints, matchersSet[0]...)
 	}
 
-	// Generate the response merging all series sets.
-	result := &client.MetricsForLabelMatchersResponse{
-		Metric: make([]*cortexpb.Metric, 0),
-	}
-
 	cnt := 0
 	for mergedSet.Next() {
 		cnt++
 		// Interrupt if the context has been canceled.
 		if cnt%util.CheckContextEveryNIterations == 0 && ctx.Err() != nil {
-			return nil, cleanup, ctx.Err()
+			return cleanup, ctx.Err()
+		}
+		if err := acc(mergedSet.At().Labels()); err != nil {
+			return cleanup, err
 		}
 
-		result.Metric = append(result.Metric, &cortexpb.Metric{
-			Labels: cortexpb.FromLabelsToLabelAdapters(mergedSet.At().Labels()),
-		})
-		if limit > 0 && len(result.Metric) >= limit {
+		if limit > 0 && cnt >= limit {
 			break
 		}
 	}
 
-	return result, cleanup, nil
+	return cleanup, nil
 }
 
 // MetricsMetadata returns all the metric metadata of a user.

pkg/ingester/ingester_test.go

@@ -2958,6 +2958,12 @@ func Test_Ingester_MetricsForLabelMatchers(t *testing.T) {
 			res, err := i.MetricsForLabelMatchers(ctx, req)
 			require.NoError(t, err)
 			assert.ElementsMatch(t, testData.expected, res.Metric)
+
+			// Stream
+			ss := mockMetricsForLabelMatchersStreamServer{ctx: ctx}
+			err = i.MetricsForLabelMatchersStream(req, &ss)
+			require.NoError(t, err)
+			assert.ElementsMatch(t, testData.expected, ss.res.Metric)
 		})
 	}
 }
@@ -3292,6 +3298,21 @@ func writeRequestSingleSeries(lbls labels.Labels, samples []cortexpb.Sample) *co
 	return req
 }
 
+type mockMetricsForLabelMatchersStreamServer struct {
+	grpc.ServerStream
+	ctx context.Context
+	res client.MetricsForLabelMatchersStreamResponse
+}
+
+func (m *mockMetricsForLabelMatchersStreamServer) Send(response *client.MetricsForLabelMatchersStreamResponse) error {
+	m.res.Metric = append(m.res.Metric, response.Metric...)
+	return nil
+}
+
+func (m *mockMetricsForLabelMatchersStreamServer) Context() context.Context {
+	return m.ctx
+}
+
 type mockQueryStreamServer struct {
 	grpc.ServerStream
 	ctx context.Context