Fix: Support custom propagators in startup log (#2925)

ddtrace/tracer/log.go

@@ -92,7 +92,18 @@ func logStartup(t *tracer) {
 		featureFlags = append(featureFlags, f)
 	}
 
-	cp, _ := t.config.propagator.(*chainedPropagator)
+	var injectorNames, extractorNames string
+	switch v := t.config.propagator.(type) {
+	case *chainedPropagator:
+		injectorNames = v.injectorNames
+		extractorNames = v.extractorsNames
+	case nil:
+		injectorNames = ""
+		extractorNames = ""
+	default:
+		injectorNames = "custom"
+		extractorNames = "custom"
+	}
 
 	info := startupInfo{
 		Date:                        time.Now().Format(time.RFC3339),
@@ -127,8 +138,8 @@ func logStartup(t *tracer) {
 		PartialFlushMinSpans:        t.config.partialFlushMinSpans,
 		Orchestrion:                 t.config.orchestrionCfg,
 		FeatureFlags:                featureFlags,
-		PropagationStyleInject:      cp.injectorNames,
-		PropagationStyleExtract:     cp.extractorsNames,
+		PropagationStyleInject:      injectorNames,
+		PropagationStyleExtract:     extractorNames,
 	}
 	if _, _, err := samplingRulesFromEnv(); err != nil {
 		info.SamplingRulesError = fmt.Sprintf("%s", err)

ddtrace/tracer/log_test.go

@@ -10,6 +10,7 @@ import (
 	"math"
 	"testing"
 
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
 	"gopkg.in/DataDog/dd-trace-go.v1/internal/globalconfig"
 	"gopkg.in/DataDog/dd-trace-go.v1/internal/log"
 	"gopkg.in/DataDog/dd-trace-go.v1/internal/telemetry"
@@ -187,3 +188,74 @@ func TestLogFormat(t *testing.T) {
 	assert.Len(tp.Logs(), 1)
 	assert.Regexp(logPrefixRegexp+` DEBUG: Started Span: dd.trace_id="12345" dd.span_id="12345" dd.parent_id="0", Operation: test, Resource: /, Tags: map.*, map.*`, tp.Logs()[0])
 }
+
+func TestLogPropagators(t *testing.T) {
+	t.Run("default", func(t *testing.T) {
+		assert := assert.New(t)
+		substring := `"propagation_style_inject":"datadog,tracecontext","propagation_style_extract":"datadog,tracecontext"`
+		log := setup(t, nil)
+		assert.Regexp(substring, log)
+	})
+	t.Run("datadog,tracecontext", func(t *testing.T) {
+		assert := assert.New(t)
+		t.Setenv("DD_TRACE_PROPAGATION_STYLE", "datadog,tracecontext")
+		substring := `"propagation_style_inject":"datadog,tracecontext","propagation_style_extract":"datadog,tracecontext"`
+		log := setup(t, nil)
+		assert.Regexp(substring, log)
+	})
+	t.Run("b3multi", func(t *testing.T) {
+		assert := assert.New(t)
+		t.Setenv("DD_TRACE_PROPAGATION_STYLE", "b3multi")
+		substring := `"propagation_style_inject":"b3multi","propagation_style_extract":"b3multi"`
+		log := setup(t, nil)
+		assert.Regexp(substring, log)
+	})
+	t.Run("none", func(t *testing.T) {
+		assert := assert.New(t)
+		t.Setenv("DD_TRACE_PROPAGATION_STYLE", "none")
+		substring := `"propagation_style_inject":"","propagation_style_extract":""`
+		log := setup(t, nil)
+		assert.Regexp(substring, log)
+	})
+	t.Run("different-injector-extractor", func(t *testing.T) {
+		assert := assert.New(t)
+		t.Setenv("DD_TRACE_PROPAGATION_STYLE_INJECT", "b3multi")
+		t.Setenv("DD_TRACE_PROPAGATION_STYLE_EXTRACT", "tracecontext")
+		substring := `"propagation_style_inject":"b3multi","propagation_style_extract":"tracecontext"`
+		log := setup(t, nil)
+		assert.Regexp(substring, log)
+	})
+	t.Run("custom-propagator", func(t *testing.T) {
+		assert := assert.New(t)
+		substring := `"propagation_style_inject":"custom","propagation_style_extract":"custom"`
+		p := &prop{}
+		log := setup(t, p)
+		assert.Regexp(substring, log)
+	})
+}
+
+type prop struct{}
+
+func (p *prop) Inject(context ddtrace.SpanContext, carrier interface{}) (e error) {
+	return
+}
+func (p *prop) Extract(carrier interface{}) (sctx ddtrace.SpanContext, e error) {
+	return
+}
+
+func setup(t *testing.T, customProp Propagator) string {
+	tp := new(log.RecordLogger)
+	var tracer *tracer
+	var stop func()
+	if customProp != nil {
+		tracer, _, _, stop = startTestTracer(t, WithLogger(tp), WithPropagator(customProp))
+	} else {
+		tracer, _, _, stop = startTestTracer(t, WithLogger(tp))
+	}
+	defer stop()
+	tp.Reset()
+	tp.Ignore("appsec: ", telemetry.LogPrefix)
+	logStartup(tracer)
+	require.Len(t, tp.Logs(), 2)
+	return tp.Logs()[1]
+}