Enable support for externally-defined ID generators (#1363)

* Enable support for externally-defined ID generators

* Moved the SDK's `internal.IDGenerator` interface to the `sdk/trace`
package.
* Added `trace.WithIDGenerator()` `TracerProviderOption`.

Signed-off-by: Anthony J Mirabella <a9@aneurysm9.com>

* Update CHANGELOG.md with PR info

* Address PR feedback:

* Fix IDGenerator godoc comment
* rename type defaultIDGenerator to randomIDGenerator
* rename defIDGenerator() to defaultIDGenerator()

Signed-off-by: Anthony J Mirabella <a9@aneurysm9.com>

* Rework trace.IDGenerator interface

* NewTraceID() -> NewIDs(ctx)
** Returns both TraceID and SpanID
* NewSpanID() -> NewSpanID(ctx, traceID)
** Returns only SpanID, has access to TraceID
* Both methods now receive a context, from which they may extract
information
* startSpanInternal() updated to receive a context to pass to the ID
generator

* Drop outdated comment from docblock

Co-authored-by: Krzesimir Nowak <qdlacz@gmail.com>

Co-authored-by: Krzesimir Nowak <qdlacz@gmail.com>

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)
 - `NewExporter` and `Start` functions in `go.opentelemetry.io/otel/exporters/otlp` now receive `context.Context` as a first parameter. (#1357)
 - Zipkin exporter relies on the status code for success rather than body read but still read the response body. (#1328)
 

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

@@ -15,36 +15,53 @@
 package trace // import "go.opentelemetry.io/otel/sdk/trace"
 
 import (
+	"context"
+	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 {
+	NewIDs(ctx context.Context) (trace.TraceID, trace.SpanID)
+	NewSpanID(ctx context.Context, traceID trace.TraceID) 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(ctx context.Context, traceID trace.TraceID) trace.SpanID {
 	gen.Lock()
 	defer gen.Unlock()
 	sid := trace.SpanID{}
 	gen.randSource.Read(sid[:])
 	return sid
 }
 
-// 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 {
+// NewIDs returns a non-zero trace ID and a non-zero span ID from a
+// randomly-chosen sequence.
+func (gen *randomIDGenerator) NewIDs(ctx context.Context) (trace.TraceID, trace.SpanID) {
 	gen.Lock()
 	defer gen.Unlock()
 	tid := trace.TraceID{}
 	gen.randSource.Read(tid[:])
-	return tid
+	sid := trace.SpanID{}
+	gen.randSource.Read(sid[:])
+	return tid, sid
+}
+
+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

@@ -15,6 +15,7 @@
 package trace
 
 import (
+	"context"
 	"fmt"
 	"math/rand"
 	"testing"
@@ -168,7 +169,7 @@ 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()
@@ -178,7 +179,7 @@ func TestTraceIdRatioSamplesInclusively(t *testing.T) {
 		samplerHi := TraceIDRatioBased(ratioHi)
 		samplerLo := TraceIDRatioBased(ratioLo)
 		for j := 0; j < numTraces; j++ {
-			traceID := idg.NewTraceID()
+			traceID, _ := idg.NewIDs(context.Background())
 
 			params := SamplingParameters{TraceID: traceID}
 			if samplerLo.ShouldSample(params).Decision == RecordAndSample {

sdk/trace/span.go

@@ -15,6 +15,7 @@
 package trace // import "go.opentelemetry.io/otel/sdk/trace"
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"reflect"
@@ -306,18 +307,21 @@ func (s *span) addChild() {
 	s.mu.Unlock()
 }
 
-func startSpanInternal(tr *tracer, name string, parent trace.SpanContext, remoteParent bool, o *trace.SpanConfig) *span {
+func startSpanInternal(ctx context.Context, tr *tracer, name string, parent trace.SpanContext, remoteParent bool, o *trace.SpanConfig) *span {
 	var noParent bool
 	span := &span{}
 	span.spanContext = parent
 
 	cfg := tr.provider.config.Load().(*Config)
 
 	if parent == emptySpanContext {
-		span.spanContext.TraceID = cfg.IDGenerator.NewTraceID()
+		// Generate both TraceID and SpanID
+		span.spanContext.TraceID, span.spanContext.SpanID = cfg.IDGenerator.NewIDs(ctx)
 		noParent = true
+	} else {
+		// TraceID already exists, just generate a SpanID
+		span.spanContext.SpanID = cfg.IDGenerator.NewSpanID(ctx, parent.TraceID)
 	}
-	span.spanContext.SpanID = cfg.IDGenerator.NewSpanID()
 	data := samplingData{
 		noParent:     noParent,
 		remoteParent: remoteParent,

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
@@ -263,9 +263,10 @@ func TestSampling(t *testing.T) {
 			for i := 0; i < total; i++ {
 				ctx := context.Background()
 				if tc.parent {
+					tid, sid := idg.NewIDs(ctx)
 					psc := trace.SpanContext{
-						TraceID: idg.NewTraceID(),
-						SpanID:  idg.NewSpanID(),
+						TraceID: tid,
+						SpanID:  sid,
 					}
 					if tc.sampledParent {
 						psc.TraceFlags = trace.FlagsSampled

sdk/trace/tracer.go

@@ -47,7 +47,7 @@ func (tr *tracer) Start(ctx context.Context, name string, options ...trace.SpanO
 		}
 	}
 
-	span := startSpanInternal(tr, name, parentSpanContext, remoteParent, config)
+	span := startSpanInternal(ctx, tr, name, parentSpanContext, remoteParent, config)
 	for _, l := range links {
 		span.addLink(l)
 	}