feat: respect jaeger parent sampling configuration

otelx/jaeger.go

@@ -18,9 +18,15 @@ import (
 	"go.opentelemetry.io/otel/trace"
 )
 
-// Optionally, Config.Providers.Jaeger.LocalAgentAddress can be set.
-// NOTE: If Config.Providers.Jaeger.Sampling.ServerURL is not specfied,
-// AlwaysSample is used.
+// SetupJaeger configures and returns a Jaeger tracer.
+//
+// The returned tracer will by default attempt to send spans to a local Jaeger agent.
+// Optionally, [otelx.JaegerConfig.LocalAgentAddress] can be set to specify a different target.
+//
+// By default, unless a parent sampler has taken a sampling decision, every span is sampled.
+// [otelx.JaegerSampling.TraceIdRatio] may be used to customize the sampling probability,
+// optionally alongside [otelx.JaegerSampling.ServerURL] to consult a remote server
+// for the sampling strategy to be used.
 func SetupJaeger(t *Tracer, tracerName string, c *Config) (trace.Tracer, error) {
 	host, port, err := net.SplitHostPort(c.Providers.Jaeger.LocalAgentAddress)
 	if err != nil {
@@ -45,17 +51,22 @@ func SetupJaeger(t *Tracer, tracerName string, c *Config) (trace.Tracer, error)
 	}
 
 	samplingServerURL := c.Providers.Jaeger.Sampling.ServerURL
+	traceIdRatio := c.Providers.Jaeger.Sampling.TraceIdRatio
+
+	sampler := sdktrace.TraceIDRatioBased(traceIdRatio)
 
 	if samplingServerURL != "" {
-		jaegerRemoteSampler := jaegerremote.New(
+		sampler = jaegerremote.New(
 			"jaegerremote",
 			jaegerremote.WithSamplingServerURL(samplingServerURL),
-			jaegerremote.WithInitialSampler(sdktrace.TraceIDRatioBased(c.Providers.Jaeger.Sampling.TraceIdRatio)),
+			jaegerremote.WithInitialSampler(sampler),
 		)
-		tpOpts = append(tpOpts, sdktrace.WithSampler(jaegerRemoteSampler))
-	} else {
-		tpOpts = append(tpOpts, sdktrace.WithSampler(sdktrace.AlwaysSample()))
 	}
+
+	// Respect any sampling decision taken by the client.
+	sampler = sdktrace.ParentBased(sampler)
+	tpOpts = append(tpOpts, sdktrace.WithSampler(sampler))
+
 	tp := sdktrace.NewTracerProvider(tpOpts...)
 	otel.SetTracerProvider(tp)
 

otelx/otel_test.go

@@ -13,12 +13,16 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"net/url"
+	"strings"
 	"testing"
 	"time"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/trace"
 	"golang.org/x/sync/errgroup"
 	"google.golang.org/protobuf/proto"
 
@@ -65,8 +69,8 @@ type zipkinSpanRequest struct {
 	Tags map[string]string
 }
 
-func TestJaegerTracer(t *testing.T) {
-	done := make(chan struct{})
+// runTestJaegerAgent starts a mock server listening on a random port for Jaeger spans sent over UDP.
+func runTestJaegerAgent(t *testing.T, errs *errgroup.Group, done chan<- struct{}) net.Conn {
 	addr := "127.0.0.1:0"
 
 	udpAddr, err := net.ResolveUDPAddr("udp", addr)
@@ -75,8 +79,6 @@ func TestJaegerTracer(t *testing.T) {
 	srv, err := net.ListenUDP("udp", udpAddr)
 	require.NoError(t, err)
 
-	errs := errgroup.Group{}
-
 	errs.Go(func() error {
 		t.Logf("Starting test UDP server for Jaeger spans on %s", srv.LocalAddr().String())
 
@@ -91,20 +93,32 @@ func TestJaegerTracer(t *testing.T) {
 				continue
 			}
 			if len(buf) != 0 {
-				t.Log("recieved span!")
+				t.Log("received span!")
 				done <- struct{}{}
 			}
 			break
 		}
 		return nil
 	})
 
+	return srv
+}
+
+func TestJaegerTracer(t *testing.T) {
+	done := make(chan struct{})
+	errs := errgroup.Group{}
+
+	srv := runTestJaegerAgent(t, &errs, done)
+
 	jt, err := New(testTracingComponent, logrusx.New("ory/x", "1"), &Config{
 		ServiceName: "Ory X",
 		Provider:    "jaeger",
 		Providers: ProvidersConfig{
 			Jaeger: JaegerConfig{
 				LocalAgentAddress: srv.LocalAddr().String(),
+				Sampling: JaegerSampling{
+					TraceIdRatio: 1,
+				},
 			},
 		},
 	})
@@ -123,6 +137,52 @@ func TestJaegerTracer(t *testing.T) {
 	require.NoError(t, errs.Wait())
 }
 
+func TestJaegerTracerRespectsParentSamplingDecision(t *testing.T) {
+	done := make(chan struct{})
+	errs := errgroup.Group{}
+
+	srv := runTestJaegerAgent(t, &errs, done)
+
+	jt, err := New(testTracingComponent, logrusx.New("ory/x", "1"), &Config{
+		ServiceName: "Ory X",
+		Provider:    "jaeger",
+		Providers: ProvidersConfig{
+			Jaeger: JaegerConfig{
+				LocalAgentAddress: srv.LocalAddr().String(),
+				Sampling: JaegerSampling{
+					// Effectively disable local sampling.
+					TraceIdRatio: 0,
+				},
+			},
+		},
+	})
+	require.NoError(t, err)
+
+	traceId := strings.Repeat("a", 32)
+	spanId := strings.Repeat("b", 16)
+	sampledFlag := "1"
+	traceHeaders := map[string]string{"uber-trace-id": traceId + ":" + spanId + ":0:" + sampledFlag}
+
+	ctx := otel.GetTextMapPropagator().Extract(context.Background(), propagation.MapCarrier(traceHeaders))
+	spanContext := trace.SpanContextFromContext(ctx)
+
+	assert.True(t, spanContext.IsValid())
+	assert.True(t, spanContext.IsSampled())
+	assert.True(t, spanContext.IsRemote())
+
+	trc := jt.Tracer()
+	_, span := trc.Start(ctx, "testSpan", trace.WithLinks(trace.Link{SpanContext: spanContext}))
+	span.SetAttributes(attribute.Bool("testAttribute", true))
+	span.End()
+
+	select {
+	case <-done:
+	case <-time.After(15 * time.Second):
+		t.Fatalf("Test server did not receive spans")
+	}
+	require.NoError(t, errs.Wait())
+}
+
 func TestZipkinTracer(t *testing.T) {
 	done := make(chan struct{})
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {