cortex/querier: fix analysis merging (#7179)

We were not merging analysis properly - mergo was overwriting data.
Instead of using a whole library for this, just write two small
functions and use them. Add test to cover this.

Signed-off-by: Giedrius Statkevičius <giedrius.statkevicius@vinted.com>

go.mod

@@ -116,7 +116,6 @@ require (
 )
 
 require (
-	dario.cat/mergo v1.0.0
 	github.com/mitchellh/go-ps v1.0.0
 	github.com/onsi/gomega v1.27.10
 	github.com/prometheus-community/prom-label-proxy v0.8.1-0.20240127162815-c1195f9aabc0

go.sum

@@ -603,8 +603,6 @@ cloud.google.com/go/workflows v1.7.0/go.mod h1:JhSrZuVZWuiDfKEFxU0/F1PQjmpnpcoIS
 cloud.google.com/go/workflows v1.8.0/go.mod h1:ysGhmEajwZxGn1OhGOGKsTXc5PyxOc0vfKf5Af+to4M=
 cloud.google.com/go/workflows v1.9.0/go.mod h1:ZGkj1aFIOd9c8Gerkjjq7OW7I5+l6cSvT3ujaO/WwSA=
 cloud.google.com/go/workflows v1.10.0/go.mod h1:fZ8LmRmZQWacon9UCX1r/g/DfAXx5VcPALq2CxzdePw=
-dario.cat/mergo v1.0.0 h1:AGCNq9Evsj31mOgNPcLyXc+4PNABt905YmuqPYYpBWk=
-dario.cat/mergo v1.0.0/go.mod h1:uNxQE+84aUszobStD9th8a29P2fMDhsBdgRYvZOxGmk=
 dmitri.shuralyov.com/gpu/mtl v0.0.0-20190408044501-666a987793e9/go.mod h1:H6x//7gZCb22OMCxBHrMx7a5I7Hp++hsVxbQ4BYO7hU=
 gioui.org v0.0.0-20210308172011-57750fc8a0a6/go.mod h1:RSH6KIUZ0p2xy5zHDxgAM4zumjgTw83q2ge/PI+yyw8=
 git.sr.ht/~sbinet/gg v0.3.1/go.mod h1:KGYtlADtqsqANL9ueOFkWymvzUvLMQllU5Ixo+8v3pc=

internal/cortex/querier/queryrange/query_range.go

@@ -12,14 +12,12 @@ import (
 	"math"
 	"net/http"
 	"net/url"
-	"reflect"
 	"sort"
 	"strconv"
 	"strings"
 	"time"
 	"unsafe"
 
-	"dario.cat/mergo"
 	"github.com/gogo/protobuf/proto"
 	github_com_gogo_protobuf_types "github.com/gogo/protobuf/types"
 	"github.com/gogo/status"
@@ -211,22 +209,38 @@ func NewEmptyPrometheusInstantQueryResponse() *PrometheusInstantQueryResponse {
 	}
 }
 
-type TimeDurationTransformer struct{}
+func traverseAnalysis(a *Analysis, results *[]*Analysis) {
+	if a == nil {
+		return
+	}
 
-func (t TimeDurationTransformer) Transformer(typ reflect.Type) func(dst, src reflect.Value) error {
-	if typ == reflect.TypeOf(Duration(0)) {
-		return func(dst, src reflect.Value) error {
-			if dst.CanSet() {
-				d := dst.Interface().(Duration)
-				s := src.Interface().(Duration)
+	*results = append(*results, a)
 
-				merged := d + s
-				dst.Set(reflect.ValueOf(merged))
-			}
-			return nil
+	for _, ch := range a.Children {
+		traverseAnalysis(ch, results)
+	}
+}
+
+func AnalyzesMerge(analysis ...*Analysis) *Analysis {
+	if len(analysis) == 0 {
+		return &Analysis{}
+	}
+
+	root := analysis[0]
+
+	var rootElements []*Analysis
+	traverseAnalysis(root, &rootElements)
+
+	for _, a := range analysis[1:] {
+		var elements []*Analysis
+		traverseAnalysis(a, &elements)
+
+		for i := 0; i < len(elements) && i < len(rootElements); i++ {
+			rootElements[i].ExecutionTime += analysis[i].ExecutionTime
 		}
 	}
-	return nil
+
+	return root
 }
 
 func (prometheusCodec) MergeResponse(_ Request, responses ...Response) (Response, error) {
@@ -246,18 +260,13 @@ func (prometheusCodec) MergeResponse(_ Request, responses ...Response) (Response
 	// Merge the responses.
 	sort.Sort(byFirstTime(promResponses))
 
-	var analysis Analysis
+	analyzes := make([]*Analysis, 0, len(responses))
 	for i := range promResponses {
 		if promResponses[i].Data.GetAnalysis() == nil {
 			continue
 		}
 
-		if err := mergo.Merge(&analysis,
-			promResponses[i].Data.GetAnalysis(),
-			mergo.WithTransformers(TimeDurationTransformer{}),
-		); err != nil {
-			return nil, err
-		}
+		analyzes = append(analyzes, promResponses[i].Data.GetAnalysis())
 	}
 
 	response := PrometheusResponse{
@@ -266,7 +275,7 @@ func (prometheusCodec) MergeResponse(_ Request, responses ...Response) (Response
 			ResultType: model.ValMatrix.String(),
 			Result:     matrixMerge(promResponses),
 			Stats:      StatsMerge(responses),
-			Analysis:   &analysis,
+			Analysis:   AnalyzesMerge(analyzes...),
 		},
 	}
 

internal/cortex/querier/queryrange/query_range_test.go

@@ -344,6 +344,72 @@ func TestMergeAPIResponses(t *testing.T) {
 			},
 		},
 
+		{
+			name: "Basic merging of two responses with nested analysis trees.",
+			input: []Response{
+				&PrometheusResponse{
+					Data: PrometheusData{
+						ResultType: matrix,
+						Analysis: &Analysis{
+							Name:          "foo",
+							Children:      []*Analysis{{Name: "bar", ExecutionTime: Duration(1 * time.Second)}},
+							ExecutionTime: Duration(1 * time.Second),
+						},
+						Result: []SampleStream{
+							{
+								Labels: []cortexpb.LabelAdapter{},
+								Samples: []cortexpb.Sample{
+									{Value: 0, TimestampMs: 0},
+									{Value: 1, TimestampMs: 1},
+								},
+							},
+						},
+					},
+				},
+				&PrometheusResponse{
+					Data: PrometheusData{
+						ResultType: matrix,
+						Analysis: &Analysis{
+							Name:          "foo",
+							Children:      []*Analysis{{Name: "bar", ExecutionTime: Duration(1 * time.Second)}},
+							ExecutionTime: Duration(1 * time.Second),
+						},
+						Result: []SampleStream{
+							{
+								Labels: []cortexpb.LabelAdapter{},
+								Samples: []cortexpb.Sample{
+									{Value: 2, TimestampMs: 2},
+									{Value: 3, TimestampMs: 3},
+								},
+							},
+						},
+					},
+				},
+			},
+			expected: &PrometheusResponse{
+				Status: StatusSuccess,
+				Data: PrometheusData{
+					ResultType: matrix,
+					Analysis: &Analysis{
+						Name:          "foo",
+						Children:      []*Analysis{{Name: "bar", ExecutionTime: Duration(2 * time.Second)}},
+						ExecutionTime: Duration(2 * time.Second),
+					},
+					Result: []SampleStream{
+						{
+							Labels: []cortexpb.LabelAdapter{},
+							Samples: []cortexpb.Sample{
+								{Value: 0, TimestampMs: 0},
+								{Value: 1, TimestampMs: 1},
+								{Value: 2, TimestampMs: 2},
+								{Value: 3, TimestampMs: 3},
+							},
+						},
+					},
+				},
+			},
+		},
+
 		{
 			name: "Merging of responses when labels are in different order.",
 			input: []Response{

pkg/queryfrontend/queryinstant_codec.go

@@ -14,7 +14,6 @@ import (
 	"strconv"
 	"strings"
 
-	"dario.cat/mergo"
 	"github.com/opentracing/opentracing-go"
 	otlog "github.com/opentracing/opentracing-go/log"
 	"github.com/prometheus/common/model"
@@ -55,18 +54,13 @@ func (c queryInstantCodec) MergeResponse(req queryrange.Request, responses ...qu
 		promResponses = append(promResponses, resp.(*queryrange.PrometheusInstantQueryResponse))
 	}
 
-	var analysis queryrange.Analysis
+	var analyzes []*queryrange.Analysis
 	for i := range promResponses {
 		if promResponses[i].Data.GetAnalysis() == nil {
 			continue
 		}
 
-		if err := mergo.Merge(&analysis,
-			promResponses[i].Data.GetAnalysis(),
-			mergo.WithTransformers(queryrange.TimeDurationTransformer{}),
-		); err != nil {
-			return nil, err
-		}
+		analyzes = append(analyzes, promResponses[i].Data.GetAnalysis())
 	}
 
 	var res queryrange.Response
@@ -81,7 +75,7 @@ func (c queryInstantCodec) MergeResponse(req queryrange.Request, responses ...qu
 						Matrix: matrixMerge(promResponses),
 					},
 				},
-				Analysis: &analysis,
+				Analysis: queryrange.AnalyzesMerge(analyzes...),
 				Stats:    queryrange.StatsMerge(responses),
 			},
 		}
@@ -99,7 +93,7 @@ func (c queryInstantCodec) MergeResponse(req queryrange.Request, responses ...qu
 						Vector: v,
 					},
 				},
-				Analysis: &analysis,
+				Analysis: queryrange.AnalyzesMerge(analyzes...),
 				Stats:    queryrange.StatsMerge(responses),
 			},
 		}