Add bytes fetched in query frontend (#37)

internal/cortex/querier/queryrange/query_bytes_fetched.go

@@ -0,0 +1,54 @@
+// Copyright (c) The Cortex Authors.
+// Licensed under the Apache License 2.0.
+
+package queryrange
+
+import (
+	"strconv"
+)
+
+// QueryBytesFetchedHeaderName is the http header name of number of bytes fetched by a query from m3readcoord.
+// This name is compatible with M3 and rule manager code
+const QueryBytesFetchedHeaderName = "M3-Fetched-Bytes-Estimate"
+
+func sumQueryBytesFetched(responses ...Response) uint64 {
+	var result uint64
+	result = 0
+	for _, resp := range responses {
+		for _, hdr := range resp.GetHeaders() {
+			if hdr.GetName() == QueryBytesFetchedHeaderName {
+				for _, v := range hdr.GetValues() {
+					n, err := strconv.ParseUint(v, 10, 64)
+					if err != nil {
+						continue
+					}
+					result += n
+				}
+				break
+			}
+		}
+	}
+	return result
+}
+
+func QueryBytesFetchedPrometheusResponseHeaders(responses ...Response) []*PrometheusResponseHeader {
+	n := sumQueryBytesFetched(responses...)
+	if n == 0 {
+		return nil
+	}
+	return []*PrometheusResponseHeader{{
+		Name:   QueryBytesFetchedHeaderName,
+		Values: []string{strconv.FormatUint(n, 10)},
+	}}
+}
+
+func QueryBytesFetchedHttpHeaderValue(response Response) []string {
+	var result []string
+	for _, hdr := range response.GetHeaders() {
+		if hdr.GetName() == QueryBytesFetchedHeaderName {
+			result = hdr.GetValues()
+			break
+		}
+	}
+	return result
+}

internal/cortex/querier/queryrange/query_bytes_fetched_test.go

@@ -0,0 +1,20 @@
+// Copyright (c) The Cortex Authors.
+// Licensed under the Apache License 2.0.
+
+package queryrange
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestQueryBytesFetchedPrometheusResponseHeaders(t *testing.T) {
+	resp1 := PrometheusResponse{Headers: []*PrometheusResponseHeader{&PrometheusResponseHeader{Name: "M3-Fetched-Bytes-Estimate", Values: []string{"100"}}}}
+	resp2 := PrometheusResponse{Headers: []*PrometheusResponseHeader{&PrometheusResponseHeader{Name: "M3-Fetched-Bytes-Estimate", Values: []string{"1000"}}}}
+	resp3 := PrometheusResponse{}
+	hdrs := QueryBytesFetchedPrometheusResponseHeaders(&resp1, &resp2, &resp3)
+	expected := []*PrometheusResponseHeader{{Name: QueryBytesFetchedHeaderName,
+		Values: []string{"1100"}}}
+	require.Equal(t, hdrs, expected)
+}

internal/cortex/querier/queryrange/query_range.go

@@ -8,7 +8,7 @@ import (
 	"context"
 	stdjson "encoding/json"
 	"fmt"
-	io "io"
+	"io"
 	"math"
 	"net/http"
 	"net/url"
@@ -278,12 +278,12 @@ func (prometheusCodec) MergeResponse(_ Request, responses ...Response) (Response
 			Analysis:   AnalyzesMerge(analyzes...),
 		},
 	}
-
+	response.Headers = QueryBytesFetchedPrometheusResponseHeaders(responses...)
 	if len(resultsCacheGenNumberHeaderValues) != 0 {
-		response.Headers = []*PrometheusResponseHeader{{
+		response.Headers = append(response.Headers, &PrometheusResponseHeader{
 			Name:   ResultsCacheGenNumberHeaderName,
 			Values: resultsCacheGenNumberHeaderValues,
-		}}
+		})
 	}
 
 	return &response, nil
@@ -447,10 +447,13 @@ func (prometheusCodec) EncodeResponse(ctx context.Context, res Response) (*http.
 
 	sp.LogFields(otlog.Int("bytes", len(b)))
 
+	httpHeader := http.Header{
+		"Content-Type": []string{"application/json"}}
+	if queryBytesFetchedHttpHeaderValue := QueryBytesFetchedHttpHeaderValue(res); queryBytesFetchedHttpHeaderValue != nil {
+		httpHeader[QueryBytesFetchedHeaderName] = queryBytesFetchedHttpHeaderValue
+	}
 	resp := http.Response{
-		Header: http.Header{
-			"Content-Type": []string{"application/json"},
-		},
+		Header:        httpHeader,
 		Body:          io.NopCloser(bytes.NewBuffer(b)),
 		StatusCode:    http.StatusOK,
 		ContentLength: int64(len(b)),

pkg/queryfrontend/queryinstant_codec.go

@@ -78,6 +78,7 @@ func (c queryInstantCodec) MergeResponse(req queryrange.Request, responses ...qu
 				Analysis: queryrange.AnalyzesMerge(analyzes...),
 				Stats:    queryrange.StatsMerge(responses),
 			},
+			Headers: queryrange.QueryBytesFetchedPrometheusResponseHeaders(responses...),
 		}
 	default:
 		v, err := vectorMerge(req, promResponses)
@@ -96,6 +97,7 @@ func (c queryInstantCodec) MergeResponse(req queryrange.Request, responses ...qu
 				Analysis: queryrange.AnalyzesMerge(analyzes...),
 				Stats:    queryrange.StatsMerge(responses),
 			},
+			Headers: queryrange.QueryBytesFetchedPrometheusResponseHeaders(responses...),
 		}
 	}
 
@@ -248,7 +250,8 @@ func (c queryInstantCodec) EncodeResponse(ctx context.Context, res queryrange.Re
 
 	resp := http.Response{
 		Header: http.Header{
-			"Content-Type": []string{"application/json"},
+			"Content-Type":                         []string{"application/json"},
+			queryrange.QueryBytesFetchedHeaderName: queryrange.QueryBytesFetchedHttpHeaderValue(res),
 		},
 		Body:          io.NopCloser(bytes.NewBuffer(b)),
 		StatusCode:    http.StatusOK,