processors/baggage: add baggage span processor

Fixes open-telemetry#5397

Signed-off-by: Alex Boten <223565+codeboten@users.noreply.github.com>

CHANGELOG.md

@@ -12,6 +12,8 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 - Add the new `go.opentelemetry.io/contrib/instrgen` package to provide auto-generated source code instrumentation. (#3068, #3108)
 - `NewSDK` in `go.opentelemetry.io/contrib/config` now returns a configured SDK with a valid `MeterProvider`. (#4804)
+- The `go.opentelemetry.io/contrib/processors/baggage` module.
+  This module provides a Baggage Span Processor. (#5397)
 
 ### Changed
 

CODEOWNERS

@@ -46,6 +46,8 @@ instrumentation/net/http/httptrace/otelhttptrace/                       @open-te
 instrumentation/net/http/otelhttp/                                      @open-telemetry/go-approvers @Aneurysm9 @dmathieu
 instrumentation/runtime/                                                @open-telemetry/go-approvers @MadVikingGod
 
+processors/baggage/                                                     @open-telemetry/go-approvers @codeboten
+
 propagators/autoprop/                                                   @open-telemetry/go-approvers @MrAlias
 propagators/aws/                                                        @open-telemetry/go-approvers @Aneurysm9
 propagators/b3/                                                         @open-telemetry/go-approvers @pellared

processors/baggage/doc.go

@@ -0,0 +1,7 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+// Package baggage implements the baggage span processor which duplicates
+// onto a span the attributes found in Baggage in the parent context at
+// the moment the span is started.
+package baggage // import "go.opentelemetry.io/contrib/processors/baggage"

processors/baggage/go.mod

@@ -0,0 +1,20 @@
+module go.opentelemetry.io/contrib/processors/baggage
+
+go 1.21
+
+require (
+	github.com/stretchr/testify v1.9.0
+	go.opentelemetry.io/otel v1.25.0
+	go.opentelemetry.io/otel/sdk v1.25.0
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/go-logr/logr v1.4.1 // indirect
+	github.com/go-logr/stdr v1.2.2 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	go.opentelemetry.io/otel/metric v1.25.0 // indirect
+	go.opentelemetry.io/otel/trace v1.25.0 // indirect
+	golang.org/x/sys v0.18.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

processors/baggage/go.sum

@@ -0,0 +1,27 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
+github.com/go-logr/logr v1.4.1 h1:pKouT5E8xu9zeFC39JXRDukb6JFQPXM5p5I91188VAQ=
+github.com/go-logr/logr v1.4.1/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
+github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
+github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
+github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+go.opentelemetry.io/otel v1.25.0 h1:gldB5FfhRl7OJQbUHt/8s0a7cE8fbsPAtdpRaApKy4k=
+go.opentelemetry.io/otel v1.25.0/go.mod h1:Wa2ds5NOXEMkCmUou1WA7ZBfLTHWIsp034OVD7AO+Vg=
+go.opentelemetry.io/otel/metric v1.25.0 h1:LUKbS7ArpFL/I2jJHdJcqMGxkRdxpPHE0VU/D4NuEwA=
+go.opentelemetry.io/otel/metric v1.25.0/go.mod h1:rkDLUSd2lC5lq2dFNrX9LGAbINP5B7WBkC78RXCpH5s=
+go.opentelemetry.io/otel/sdk v1.25.0 h1:PDryEJPC8YJZQSyLY5eqLeafHtG+X7FWnf3aXMtxbqo=
+go.opentelemetry.io/otel/sdk v1.25.0/go.mod h1:oFgzCM2zdsxKzz6zwpTZYLLQsFwc+K0daArPdIhuxkw=
+go.opentelemetry.io/otel/trace v1.25.0 h1:tqukZGLwQYRIFtSQM2u2+yfMVTgGVeqRLPUYx1Dq6RM=
+go.opentelemetry.io/otel/trace v1.25.0/go.mod h1:hCCs70XM/ljO+BeQkyFnbK28SBIJ/Emuha+ccrCRT7I=
+golang.org/x/sys v0.18.0 h1:DBdB3niSjOA/O0blCZBqDefyWNYveAYMNF1Wum0DYQ4=
+golang.org/x/sys v0.18.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

processors/baggage/processor.go

@@ -0,0 +1,35 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package baggage
+
+import (
+	"context"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/baggage"
+	"go.opentelemetry.io/otel/sdk/trace"
+)
+
+type baggageSpanProcessor struct{}
+
+var _ trace.SpanProcessor = (*baggageSpanProcessor)(nil)
+
+// Returns a new baggageSpanProcessor.
+//
+// The Baggage span processor duplicates onto a span the attributes found
+// in Baggage in the parent context at the moment the span is started.
+func NewBaggageSpanProcessor() trace.SpanProcessor {
+	return &baggageSpanProcessor{}
+}
+
+func (processor baggageSpanProcessor) OnStart(ctx context.Context, span trace.ReadWriteSpan) {
+	baggage := baggage.FromContext(ctx)
+	for _, entry := range baggage.Members() {
+		span.SetAttributes(attribute.String(entry.Key(), entry.Value()))
+	}
+}
+
+func (processor baggageSpanProcessor) OnEnd(s trace.ReadOnlySpan)       {}
+func (processor baggageSpanProcessor) Shutdown(context.Context) error   { return nil }
+func (processor baggageSpanProcessor) ForceFlush(context.Context) error { return nil }

processors/baggage/processor_test.go

@@ -0,0 +1,62 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package baggage
+
+import (
+	"context"
+	"net/url"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/baggage"
+	"go.opentelemetry.io/otel/sdk/trace"
+)
+
+var _ trace.SpanExporter = &testExporter{}
+
+type testExporter struct {
+	spans []trace.ReadOnlySpan
+}
+
+func (e *testExporter) Start(ctx context.Context) error    { return nil }
+func (e *testExporter) Shutdown(ctx context.Context) error { return nil }
+
+func (e *testExporter) ExportSpans(ctx context.Context, ss []trace.ReadOnlySpan) error {
+	e.spans = append(e.spans, ss...)
+	return nil
+}
+
+func NewTestExporter() *testExporter {
+	return &testExporter{}
+}
+
+func TestBaggageSpanProcessorAppendsBaggageAttributes(t *testing.T) {
+	// create ctx with some baggage
+	ctx := context.Background()
+	suitcase := baggage.FromContext(ctx)
+	packingCube, _ := baggage.NewMember("baggage.test", url.PathEscape("baggage value"))
+	suitcase, _ = suitcase.SetMember(packingCube)
+	ctx = baggage.ContextWithBaggage(ctx, suitcase)
+
+	// create trace provider with baggage processor and test exporter
+	exporter := NewTestExporter()
+	tp := trace.NewTracerProvider(
+		trace.WithSpanProcessor(NewBaggageSpanProcessor()),
+		trace.WithSpanProcessor(trace.NewSimpleSpanProcessor(exporter)),
+	)
+
+	// create tracer and start/end span
+	tracer := tp.Tracer("test")
+	_, span := tracer.Start(ctx, "test")
+	span.End()
+
+	assert.Equal(t, 1, len(exporter.spans))
+	assert.Equal(t, 1, len(exporter.spans[0].Attributes()))
+
+	for _, attr := range exporter.spans[0].Attributes() {
+		assert.Equal(t, attribute.Key("baggage.test"), attr.Key)
+		assert.Equal(t, "baggage value", attr.Value.AsString())
+	}
+}

versions.yaml

@@ -77,6 +77,10 @@ module-sets:
     version: v0.0.1
     modules:
       - go.opentelemetry.io/contrib/bridges/otelslog
+  experimental-processors:
+    version: v0.0.1
+    modules:
+      - go.opentelemetry.io/contrib/processors/baggage
 excluded-modules:
   - go.opentelemetry.io/contrib/instrgen
   - go.opentelemetry.io/contrib/instrgen/driver