Enable support for externally-defined ID generators

CHANGELOG.md

@@ -8,9 +8,14 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+### Added
+
+- `trace.WithIDGenerator()` `TracerProviderOption`. (#1363)
+
 ### Changed
 
 - Move the OpenCensus example into `example` directory. (#1359)
+- Moved the SDK's `internal.IDGenerator` interface in to the `sdk/trace` package to enable support for externally-defined ID generators. (#1363)
 
 ## [0.14.0] - 2020-11-19
 

sdk/trace/config.go

@@ -16,7 +16,6 @@ package trace // import "go.opentelemetry.io/otel/sdk/trace"
 
 import (
 	"go.opentelemetry.io/otel/sdk/resource"
-	"go.opentelemetry.io/otel/sdk/trace/internal"
 )
 
 // Config represents the global tracing configuration.
@@ -25,7 +24,7 @@ type Config struct {
 	DefaultSampler Sampler
 
 	// IDGenerator is for internal use only.
-	IDGenerator internal.IDGenerator
+	IDGenerator IDGenerator
 
 	// MaxEventsPerSpan is max number of message events per span
 	MaxEventsPerSpan int

sdk/trace/id_generator.go

@@ -15,23 +15,29 @@
 package trace // import "go.opentelemetry.io/otel/sdk/trace"
 
 import (
+	crand "crypto/rand"
+	"encoding/binary"
 	"math/rand"
 	"sync"
 
 	"go.opentelemetry.io/otel/trace"
-
-	"go.opentelemetry.io/otel/sdk/trace/internal"
 )
 
-type defaultIDGenerator struct {
+// IDGenerator allows custom generators for TraceID and SpanID.
+type IDGenerator interface {
+	NewTraceID() trace.TraceID
+	NewSpanID() trace.SpanID
+}
+
+type randomIDGenerator struct {
 	sync.Mutex
 	randSource *rand.Rand
 }
 
-var _ internal.IDGenerator = &defaultIDGenerator{}
+var _ IDGenerator = &randomIDGenerator{}
 
 // NewSpanID returns a non-zero span ID from a randomly-chosen sequence.
-func (gen *defaultIDGenerator) NewSpanID() trace.SpanID {
+func (gen *randomIDGenerator) NewSpanID() trace.SpanID {
 	gen.Lock()
 	defer gen.Unlock()
 	sid := trace.SpanID{}
@@ -41,10 +47,18 @@ func (gen *defaultIDGenerator) NewSpanID() trace.SpanID {
 
 // NewTraceID returns a non-zero trace ID from a randomly-chosen sequence.
 // mu should be held while this function is called.
-func (gen *defaultIDGenerator) NewTraceID() trace.TraceID {
+func (gen *randomIDGenerator) NewTraceID() trace.TraceID {
 	gen.Lock()
 	defer gen.Unlock()
 	tid := trace.TraceID{}
 	gen.randSource.Read(tid[:])
 	return tid
 }
+
+func defaultIDGenerator() IDGenerator {
+	gen := &randomIDGenerator{}
+	var rngSeed int64
+	_ = binary.Read(crand.Reader, binary.LittleEndian, &rngSeed)
+	gen.randSource = rand.New(rand.NewSource(rngSeed))
+	return gen
+}

sdk/trace/provider.go

@@ -66,7 +66,7 @@ func NewTracerProvider(opts ...TracerProviderOption) *TracerProvider {
 	}
 	tp.config.Store(&Config{
 		DefaultSampler:       ParentBased(AlwaysSample()),
-		IDGenerator:          defIDGenerator(),
+		IDGenerator:          defaultIDGenerator(),
 		MaxAttributesPerSpan: DefaultMaxAttributesPerSpan,
 		MaxEventsPerSpan:     DefaultMaxEventsPerSpan,
 		MaxLinksPerSpan:      DefaultMaxLinksPerSpan,
@@ -231,3 +231,10 @@ func WithResource(r *resource.Resource) TracerProviderOption {
 		opts.config.Resource = r
 	}
 }
+
+// WithIDGenerator option registers an IDGenerator with the TracerProvider.
+func WithIDGenerator(g IDGenerator) TracerProviderOption {
+	return func(opts *TracerProviderConfig) {
+		opts.config.IDGenerator = g
+	}
+}

sdk/trace/sampling_test.go

@@ -168,7 +168,7 @@ func TestTraceIdRatioSamplesInclusively(t *testing.T) {
 		numSamplers = 1000
 		numTraces   = 100
 	)
-	idg := defIDGenerator()
+	idg := defaultIDGenerator()
 
 	for i := 0; i < numSamplers; i++ {
 		ratioLo, ratioHi := rand.Float64(), rand.Float64()

sdk/trace/trace_test.go

@@ -213,7 +213,7 @@ func TestRecordingIsOn(t *testing.T) {
 }
 
 func TestSampling(t *testing.T) {
-	idg := defIDGenerator()
+	idg := defaultIDGenerator()
 	const total = 10000
 	for name, tc := range map[string]struct {
 		sampler       Sampler