From a291faad71cf870dc7fe19133399d2e4e40fa6f2 Mon Sep 17 00:00:00 2001
From: Aleksander Mistewicz <amistewicz@google.com>
Date: Wed, 9 Jul 2025 10:55:13 +0200
Subject: [PATCH] Add OTEL tracing to Range and Txn

Signed-off-by: Aleksander Mistewicz <amistewicz@google.com>
---
 pkg/go.mod                     |  1 +
 pkg/traceutil/trace.go         | 10 ++++++++++
 server/embed/config_tracing.go |  4 ++++
 server/etcdserver/v3_server.go | 34 ++++++++++++++++++++++++++++++++++
 server/go.mod                  |  2 +-
 5 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/pkg/go.mod b/pkg/go.mod
index 2081725f8..3f30f4b9c 100644
--- a/pkg/go.mod
+++ b/pkg/go.mod
@@ -11,6 +11,7 @@ require (
 	github.com/spf13/pflag v1.0.6
 	github.com/stretchr/testify v1.10.0
 	go.etcd.io/etcd/client/pkg/v3 v3.6.0-alpha.0
+	go.opentelemetry.io/otel/trace v1.37.0
 	go.uber.org/zap v1.27.0
 	google.golang.org/grpc v1.73.0
 )
diff --git a/pkg/traceutil/trace.go b/pkg/traceutil/trace.go
index cd75a9e60..f89ba83c9 100644
--- a/pkg/traceutil/trace.go
+++ b/pkg/traceutil/trace.go
@@ -22,9 +22,19 @@ import (
 	"strings"
 	"time"
 
+	"go.opentelemetry.io/otel/trace"
+	"go.opentelemetry.io/otel/trace/noop"
 	"go.uber.org/zap"
 )
 
+const instrumentationScope = "go.etcd.io/etcd"
+
+var Tracer trace.Tracer = noop.NewTracerProvider().Tracer(instrumentationScope)
+
+func Init(tp trace.TracerProvider) {
+	Tracer = tp.Tracer(instrumentationScope)
+}
+
 // TraceKey is used as a key of context for Trace.
 type TraceKey struct{}
 
diff --git a/server/embed/config_tracing.go b/server/embed/config_tracing.go
index 0ca90fdc5..7fa985a75 100644
--- a/server/embed/config_tracing.go
+++ b/server/embed/config_tracing.go
@@ -25,6 +25,8 @@ import (
 	tracesdk "go.opentelemetry.io/otel/sdk/trace"
 	semconv "go.opentelemetry.io/otel/semconv/v1.17.0"
 	"go.uber.org/zap"
+
+	"go.etcd.io/etcd/pkg/v3/traceutil"
 )
 
 const maxSamplingRatePerMillion = 1000000
@@ -81,6 +83,8 @@ func newTracingExporter(ctx context.Context, cfg *Config) (*tracingExporter, err
 		),
 	)
 
+	traceutil.Init(traceProvider)
+
 	options := []otelgrpc.Option{
 		otelgrpc.WithPropagators(
 			propagation.NewCompositeTextMapPropagator(
diff --git a/server/etcdserver/v3_server.go b/server/etcdserver/v3_server.go
index cd85cf988..fb8f88aad 100644
--- a/server/etcdserver/v3_server.go
+++ b/server/etcdserver/v3_server.go
@@ -24,6 +24,8 @@ import (
 	"time"
 
 	"github.com/gogo/protobuf/proto"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/trace"
 	"go.uber.org/zap"
 	"golang.org/x/crypto/bcrypt"
 
@@ -102,6 +104,16 @@ type Authenticator interface {
 }
 
 func (s *EtcdServer) Range(ctx context.Context, r *pb.RangeRequest) (*pb.RangeResponse, error) {
+	var span trace.Span
+	ctx, span = traceutil.Tracer.Start(ctx, "range", trace.WithAttributes(
+		attribute.String("range_begin", string(r.GetKey())),
+		attribute.String("range_end", string(r.GetRangeEnd())),
+		attribute.Int64("rev", r.GetRevision()),
+		attribute.Int64("limit", r.GetLimit()),
+		attribute.Bool("count_only", r.GetCountOnly()),
+	))
+	defer span.End()
+
 	ctx, trace := traceutil.EnsureTrace(ctx, s.Logger(), "range",
 		traceutil.Field{Key: "range_begin", Value: string(r.Key)},
 		traceutil.Field{Key: "range_end", Value: string(r.RangeEnd)},
@@ -156,8 +168,30 @@ func (s *EtcdServer) DeleteRange(ctx context.Context, r *pb.DeleteRangeRequest)
 	return resp.(*pb.DeleteRangeResponse), nil
 }
 
+// firstCompareKey returns first non-empty key in the list of comparison operations.
+func firstCompareKey(c []*pb.Compare) string {
+	for _, op := range c {
+		key := string(op.GetKey())
+		if key != "" {
+			return key
+		}
+	}
+	return ""
+}
+
 func (s *EtcdServer) Txn(ctx context.Context, r *pb.TxnRequest) (*pb.TxnResponse, error) {
 	readOnly := txn.IsTxnReadonly(r)
+
+	var span trace.Span
+	ctx, span = traceutil.Tracer.Start(ctx, "txn", trace.WithAttributes(
+		attribute.String("compare_first_key", firstCompareKey(r.GetCompare())),
+		attribute.Int("compare_len", len(r.GetCompare())),
+		attribute.Int("success_len", len(r.GetSuccess())),
+		attribute.Int("failure_len", len(r.GetFailure())),
+		attribute.Bool("read_only", readOnly),
+	))
+	defer span.End()
+
 	ctx, trace := traceutil.EnsureTrace(ctx, s.Logger(), "transaction",
 		traceutil.Field{Key: "read_only", Value: readOnly},
 	)
diff --git a/server/go.mod b/server/go.mod
index f8acef47e..ab53278a8 100644
--- a/server/go.mod
+++ b/server/go.mod
@@ -35,6 +35,7 @@ require (
 	go.opentelemetry.io/otel v1.37.0
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc v1.37.0
 	go.opentelemetry.io/otel/sdk v1.37.0
+	go.opentelemetry.io/otel/trace v1.37.0
 	go.uber.org/zap v1.27.0
 	golang.org/x/crypto v0.39.0
 	golang.org/x/net v0.41.0
@@ -67,7 +68,6 @@ require (
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.37.0 // indirect
 	go.opentelemetry.io/otel/metric v1.37.0 // indirect
-	go.opentelemetry.io/otel/trace v1.37.0 // indirect
 	go.opentelemetry.io/proto/otlp v1.7.0 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
 	go.yaml.in/yaml/v2 v2.4.2 // indirect