fix remote read error in query frontend

CHANGELOG.md

@@ -2,9 +2,9 @@
 
 ## master / unreleased
 * [CHANGE] Store gateways summary metrics have been converted to histograms `cortex_bucket_store_series_blocks_queried`, `cortex_bucket_store_series_data_fetched`, `cortex_bucket_store_series_data_size_touched_bytes`, `cortex_bucket_store_series_data_size_fetched_bytes`, `cortex_bucket_store_series_data_touched`, `cortex_bucket_store_series_result_series` #5239
-
 * [ENHANCEMENT] Querier: Batch Iterator optimization to prevent transversing it multiple times query ranges steps does not overlap. #5237
 * [BUGFIX] Catch context error in the s3 bucket client. #5240
+* [BUGFIX] Fix query frontend remote read empty body. #5257
 
 ## 1.15.0 in progress
 

integration/e2ecortex/client.go

@@ -19,8 +19,11 @@ import (
 	promapi "github.com/prometheus/client_golang/api"
 	promv1 "github.com/prometheus/client_golang/api/prometheus/v1"
 	"github.com/prometheus/common/model"
+	"github.com/prometheus/prometheus/model/labels"
 	"github.com/prometheus/prometheus/model/rulefmt"
 	"github.com/prometheus/prometheus/prompb"
+	"github.com/prometheus/prometheus/storage"
+	"github.com/prometheus/prometheus/storage/remote"
 	yaml "gopkg.in/yaml.v3"
 
 	"github.com/cortexproject/cortex/pkg/ruler"
@@ -153,6 +156,72 @@ func (c *Client) QueryRaw(query string) (*http.Response, []byte, error) {
 	return c.query(addr)
 }
 
+// RemoteRead runs a remote read query.
+func (c *Client) RemoteRead(matchers []*labels.Matcher, start, end time.Time, step time.Duration) (*prompb.ReadResponse, error) {
+	startMs := start.UnixMilli()
+	endMs := end.UnixMilli()
+	stepMs := step.Milliseconds()
+
+	q, err := remote.ToQuery(startMs, endMs, matchers, &storage.SelectHints{
+		Step:  stepMs,
+		Start: startMs,
+		End:   endMs,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	req := &prompb.ReadRequest{
+		Queries:               []*prompb.Query{q},
+		AcceptedResponseTypes: []prompb.ReadRequest_ResponseType{prompb.ReadRequest_STREAMED_XOR_CHUNKS},
+	}
+
+	data, err := proto.Marshal(req)
+	if err != nil {
+		return nil, err
+	}
+	compressed := snappy.Encode(nil, data)
+
+	// Call the remote read API endpoint with a timeout.
+	httpReqCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	httpReq, err := http.NewRequestWithContext(httpReqCtx, "POST", "http://"+c.querierAddress+"/prometheus/api/v1/read", bytes.NewReader(compressed))
+	if err != nil {
+		return nil, err
+	}
+	httpReq.Header.Set("X-Scope-OrgID", "user-1")
+	httpReq.Header.Add("Content-Encoding", "snappy")
+	httpReq.Header.Add("Accept-Encoding", "snappy")
+	httpReq.Header.Set("Content-Type", "application/x-protobuf")
+	httpReq.Header.Set("User-Agent", "Prometheus/1.8.2")
+	httpReq.Header.Set("X-Prometheus-Remote-Read-Version", "0.1.0")
+
+	httpResp, err := c.httpClient.Do(httpReq)
+	if err != nil {
+		return nil, err
+	}
+	if httpResp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("unexpected status code %d", httpResp.StatusCode)
+	}
+
+	compressed, err = io.ReadAll(httpResp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	uncompressed, err := snappy.Decode(nil, compressed)
+	if err != nil {
+		return nil, err
+	}
+
+	var resp prompb.ReadResponse
+	if err = proto.Unmarshal(uncompressed, &resp); err != nil {
+		return nil, err
+	}
+	return &resp, nil
+}
+
 func (c *Client) query(addr string) (*http.Response, []byte, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), c.timeout)
 	defer cancel()

integration/query_frontend_test.go

@@ -31,6 +31,7 @@ type queryFrontendTestConfig struct {
 	testMissingMetricName bool
 	querySchedulerEnabled bool
 	queryStatsEnabled     bool
+	remoteReadEnabled     bool
 	setup                 func(t *testing.T, s *e2e.Scenario) (configFile string, flags map[string]string)
 }
 
@@ -194,6 +195,19 @@ func TestQueryFrontendWithVerticalShardingQueryScheduler(t *testing.T) {
 	})
 }
 
+func TestQueryFrontendRemoteRead(t *testing.T) {
+	runQueryFrontendTest(t, queryFrontendTestConfig{
+		remoteReadEnabled: true,
+		setup: func(t *testing.T, s *e2e.Scenario) (configFile string, flags map[string]string) {
+			require.NoError(t, writeFileToSharedDir(s, cortexConfigFile, []byte(BlocksStorageConfig)))
+
+			minio := e2edb.NewMinio(9000, BlocksStorageFlags()["-blocks-storage.s3.bucket-name"])
+			require.NoError(t, s.StartAndWaitReady(minio))
+			return cortexConfigFile, flags
+		},
+	})
+}
+
 func runQueryFrontendTest(t *testing.T, cfg queryFrontendTestConfig) {
 	const numUsers = 10
 	const numQueriesPerUser = 10
@@ -307,6 +321,18 @@ func runQueryFrontendTest(t *testing.T, cfg queryFrontendTestConfig) {
 			require.Regexp(t, "querier_wall_time;dur=[0-9.]*, response_time;dur=[0-9.]*$", res.Header.Values("Server-Timing")[0])
 		}
 
+		// No need to repeat the test on remote read for each user.
+		if userID == 0 && cfg.remoteReadEnabled {
+			start := now.Add(-1 * time.Hour)
+			end := now.Add(1 * time.Hour)
+			res, err := c.RemoteRead([]*labels.Matcher{labels.MustNewMatcher(labels.MatchEqual, labels.MetricName, "series_1")}, start, end, time.Second)
+			require.NoError(t, err)
+			require.True(t, len(res.Results) > 0)
+			require.True(t, len(res.Results[0].Timeseries) > 0)
+			require.True(t, len(res.Results[0].Timeseries[0].Samples) > 0)
+			require.True(t, len(res.Results[0].Timeseries[0].Labels) > 0)
+		}
+
 		// In this test we do ensure that the /series start/end time is ignored and Cortex
 		// always returns series in ingesters memory. No need to repeat it for each user.
 		if userID == 0 {
@@ -342,6 +368,10 @@ func runQueryFrontendTest(t *testing.T, cfg queryFrontendTestConfig) {
 		extra++
 	}
 
+	if cfg.remoteReadEnabled {
+		extra++
+	}
+
 	require.NoError(t, queryFrontend.WaitSumMetrics(e2e.Equals(numUsers*numQueriesPerUser+extra), "cortex_query_frontend_queries_total"))
 
 	// The number of received request is greater than the query requests because include

pkg/frontend/transport/handler.go

@@ -139,11 +139,14 @@ func (f *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	r.Body = io.NopCloser(io.TeeReader(r.Body, &buf))
 	// We parse form here so that we can use buf as body, in order to
 	// prevent https://github.com/cortexproject/cortex/issues/5201.
-	if err := r.ParseForm(); err != nil {
-		writeError(w, err)
-		return
+	// Exclude remote read here as we don't have to buffer its body.
+	if !strings.Contains(r.URL.Path, "api/v1/read") {
+		if err := r.ParseForm(); err != nil {
+			writeError(w, err)
+			return
+		}
+		r.Body = io.NopCloser(&buf)
 	}
-	r.Body = io.NopCloser(&buf)
 
 	startTime := time.Now()
 	resp, err := f.roundTripper.RoundTrip(r)