processors/baggage: add baggage span processor

.github/dependabot.yml

@@ -541,6 +541,15 @@ updates:
     schedule:
       interval: weekly
       day: sunday
+  - package-ecosystem: gomod
+    directory: /processors/baggage/baggagetrace
+    labels:
+      - dependencies
+      - go
+      - Skip Changelog
+    schedule:
+      interval: weekly
+      day: sunday
   - package-ecosystem: gomod
     directory: /propagators/autoprop
     labels:

CHANGELOG.md

@@ -12,6 +12,7 @@ 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. (#5404)
 
 ### 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

README.md

@@ -16,6 +16,7 @@ Collection of 3rd-party packages for [OpenTelemetry-Go](https://github.com/open-
 - [Exporters](./exporters/): Packages providing OpenTelemetry exporters for 3rd-party export formats.
 - [Samplers](./samplers/): Packages providing additional implementations of OpenTelemetry samplers.
 - [Bridges](./bridges/): Packages providing adapters for 3rd-party instrumentation frameworks.
+- [Processors](./processors/): Packages providing additional implementations of OpenTelemetry processors.
 
 ## Project Status
 

processors/baggage/baggagetrace/doc.go

@@ -0,0 +1,5 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+// Package baggagetrace implements a baggage span processor.
+package baggagetrace // import "go.opentelemetry.io/contrib/processors/baggage"

processors/baggage/baggagetrace/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/baggagetrace/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/baggagetrace/processor.go

@@ -0,0 +1,42 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package baggagetrace // import "go.opentelemetry.io/contrib/processors/baggage"
+
+import (
+	"context"
+
+	"go.opentelemetry.io/otel/attribute"
+	otelbaggage "go.opentelemetry.io/otel/baggage"
+	"go.opentelemetry.io/otel/sdk/trace"
+)
+
+// SpanProcessor is a processing pipeline for spans in the trace signal.
+type SpanProcessor struct{}
+
+var _ trace.SpanProcessor = (*SpanProcessor)(nil)
+
+// New returns a new SpanProcessor.
+//
+// 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 New() trace.SpanProcessor {
+	return &SpanProcessor{}
+}
+
+// OnStart is called when a span is started and adds span attributes for baggage contents.
+func (processor SpanProcessor) OnStart(ctx context.Context, span trace.ReadWriteSpan) {
+	for _, entry := range otelbaggage.FromContext(ctx).Members() {
+		span.SetAttributes(attribute.String(entry.Key(), entry.Value()))
+	}
+}
+
+// OnEnd is called when span is finished and is a no-op for this processor.
+func (processor SpanProcessor) OnEnd(s trace.ReadOnlySpan) {}
+
+// Shutdown is called when the SDK shuts down and is a no-op for this processor.
+func (processor SpanProcessor) Shutdown(context.Context) error { return nil }
+
+// ForceFlush exports all ended spans to the configured Exporter that have not yet
+// been exported and is a no-op for this processor.
+func (processor SpanProcessor) ForceFlush(context.Context) error { return nil }

processors/baggage/baggagetrace/processor_test.go

@@ -0,0 +1,62 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package baggagetrace
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/otel/attribute"
+	otelbaggage "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 TestSpanProcessorAppendsBaggageAttributes(t *testing.T) {
+	suitcase, err := otelbaggage.New()
+	require.NoError(t, err)
+	packingCube, err := otelbaggage.NewMemberRaw("baggage.test", "baggage value")
+	require.NoError(t, err)
+	suitcase, err = suitcase.SetMember(packingCube)
+	require.NoError(t, err)
+	ctx := otelbaggage.ContextWithBaggage(context.Background(), suitcase)
+
+	// create trace provider with baggage processor and test exporter
+	exporter := NewTestExporter()
+	tp := trace.NewTracerProvider(
+		trace.WithSpanProcessor(New()),
+		trace.WithSpanProcessor(trace.NewSimpleSpanProcessor(exporter)),
+	)
+
+	// create tracer and start/end span
+	tracer := tp.Tracer("test")
+	_, span := tracer.Start(ctx, "test")
+	span.End()
+
+	assert.Len(t, exporter.spans, 1)
+	assert.Len(t, exporter.spans[0].Attributes(), 1)
+
+	want := []attribute.KeyValue{attribute.String("baggage.test", "baggage value")}
+	assert.Equal(t, want, exporter.spans[0].Attributes())
+}

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/baggagetrace
 excluded-modules:
   - go.opentelemetry.io/contrib/instrgen
   - go.opentelemetry.io/contrib/instrgen/driver