Move B3 propagator from main repo to contrib repo (#344)

* Move B3 context propagator from go.opentelemetry.io/otel repo.

* Add to dependabot.yml

* Update README.  Add doc.go

* Updated CHANGELOG to reflect addition of B3 propagator.

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

.github/dependabot.yml

@@ -309,6 +309,15 @@ updates:
       day: "sunday"
   -
     package-ecosystem: "gomod"
+    directory: "/propagators"
+    labels:
+      - dependencies
+      - go
+      - "Skip Changelog"
+    schedule:
+      interval: "weekly"
+      day: "sunday"
+  - package-ecosystem: "gomod"
     directory: "/tools"
     labels:
       - dependencies

CHANGELOG.md

@@ -13,6 +13,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Benchmark tests for the gRPC instrumentation. (#296)
 - Integration testing for the gRPC instrumentation. (#297)
 - Allow custom labels to be added to net/http metrics. (#306)
+- Added B3 propagator, moving it out of open.telemetry.io/otel repo. (#344)
 
 ### Changed
 

README.md

@@ -11,6 +11,8 @@ Collection of 3rd-party instrumentation and exporters for [OpenTelemetry-Go](htt
 
 - [Instrumentation](./instrumentation/): Packages providing OpenTelemetry instrumentation for 3rd-party libraries.
 - [Exporters](./exporters/): Packages providing OpenTelemetry exporters for 3rd-party telemetry systems.
+- [Propagators](./propagators/): Packages providing Opentelemetry context propagators for 3rd-party propagation formats.
+- [Detectors](./detectors/): Packages providing OpenTelemetry resource detectors for 3rd-party cloud computing environments.
 
 ## Contributing
 

propagators/b3/b3_benchmark_test.go

@@ -0,0 +1,103 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package b3_test
+
+import (
+	"context"
+	"net/http"
+	"testing"
+
+	"go.opentelemetry.io/contrib/propagators/b3"
+	"go.opentelemetry.io/otel/api/trace"
+)
+
+func BenchmarkExtractB3(b *testing.B) {
+	testGroup := []struct {
+		name  string
+		tests []extractTest
+	}{
+		{
+			name:  "valid headers",
+			tests: extractHeaders,
+		},
+		{
+			name:  "invalid headers",
+			tests: extractInvalidHeaders,
+		},
+	}
+
+	for _, tg := range testGroup {
+		propagator := b3.B3{}
+		for _, tt := range tg.tests {
+			traceBenchmark(tg.name+"/"+tt.name, b, func(b *testing.B) {
+				ctx := context.Background()
+				req, _ := http.NewRequest("GET", "http://example.com", nil)
+				for h, v := range tt.headers {
+					req.Header.Set(h, v)
+				}
+				b.ReportAllocs()
+				b.ResetTimer()
+				for i := 0; i < b.N; i++ {
+					_ = propagator.Extract(ctx, req.Header)
+				}
+			})
+		}
+	}
+}
+
+func BenchmarkInjectB3(b *testing.B) {
+	testGroup := []struct {
+		name  string
+		tests []injectTest
+	}{
+		{
+			name:  "valid headers",
+			tests: injectHeader,
+		},
+		{
+			name:  "invalid headers",
+			tests: injectInvalidHeader,
+		},
+	}
+
+	for _, tg := range testGroup {
+		for _, tt := range tg.tests {
+			propagator := b3.B3{InjectEncoding: tt.encoding}
+			traceBenchmark(tg.name+"/"+tt.name, b, func(b *testing.B) {
+				req, _ := http.NewRequest("GET", "http://example.com", nil)
+				ctx := trace.ContextWithSpan(
+					context.Background(),
+					testSpan{sc: tt.sc},
+				)
+				b.ReportAllocs()
+				b.ResetTimer()
+				for i := 0; i < b.N; i++ {
+					propagator.Inject(ctx, req.Header)
+				}
+			})
+		}
+	}
+}
+
+func traceBenchmark(name string, b *testing.B, fn func(*testing.B)) {
+	b.Run(name, func(b *testing.B) {
+		b.ReportAllocs()
+		fn(b)
+	})
+	b.Run(name, func(b *testing.B) {
+		b.ReportAllocs()
+		fn(b)
+	})
+}