TUN-6576: Consume cf-trace-id from incoming TCP requests to create root span

tracing/tracing.go

@@ -8,6 +8,7 @@ import (
 	"net/http"
 	"os"
 	"runtime"
+	"strings"
 
 	"github.com/rs/zerolog"
 	otelContrib "go.opentelemetry.io/contrib/propagators/jaeger"
@@ -33,6 +34,9 @@ const (
 
 	MaxErrorDescriptionLen = 100
 	traceHttpStatusCodeKey = "upstreamStatusCode"
+
+	traceID128bitsWidth = 128 / 4
+	separator           = ":"
 )
 
 var (
@@ -66,22 +70,50 @@ func Init(version string) {
 	cloudflaredVersionAttribute = semconv.ProcessRuntimeVersionKey.String(version)
 }
 
-type TracedRequest struct {
+type TracedHTTPRequest struct {
 	*http.Request
-	trace.TracerProvider
-	exporter InMemoryClient
+	*cfdTracer
 }
 
-// NewTracedRequest creates a new tracer for the current request context.
-func NewTracedRequest(req *http.Request) *TracedRequest {
+// NewTracedHTTPRequest creates a new tracer for the current HTTP request context.
+func NewTracedHTTPRequest(req *http.Request, log *zerolog.Logger) *TracedHTTPRequest {
 	ctx, exists := extractTrace(req)
 	if !exists {
-		return &TracedRequest{req, trace.NewNoopTracerProvider(), &NoopOtlpClient{}}
+		return &TracedHTTPRequest{req, &cfdTracer{trace.NewNoopTracerProvider(), &NoopOtlpClient{}, log}}
 	}
+	return &TracedHTTPRequest{req.WithContext(ctx), newCfdTracer(ctx, log)}
+}
+
+func (tr *TracedHTTPRequest) ToTracedContext() *TracedContext {
+	return &TracedContext{tr.Context(), tr.cfdTracer}
+}
+
+type TracedContext struct {
+	context.Context
+	*cfdTracer
+}
+
+// NewTracedHTTPRequest creates a new tracer for the current HTTP request context.
+func NewTracedContext(ctx context.Context, traceContext string, log *zerolog.Logger) *TracedContext {
+	ctx, exists := extractTraceFromString(ctx, traceContext)
+	if !exists {
+		return &TracedContext{ctx, &cfdTracer{trace.NewNoopTracerProvider(), &NoopOtlpClient{}, log}}
+	}
+	return &TracedContext{ctx, newCfdTracer(ctx, log)}
+}
+
+type cfdTracer struct {
+	trace.TracerProvider
+	exporter InMemoryClient
+	log      *zerolog.Logger
+}
+
+// NewCfdTracer creates a new tracer for the current request context.
+func newCfdTracer(ctx context.Context, log *zerolog.Logger) *cfdTracer {
 	mc := new(InMemoryOtlpClient)
-	exp, err := otlptrace.New(req.Context(), mc)
+	exp, err := otlptrace.New(ctx, mc)
 	if err != nil {
-		return &TracedRequest{req, trace.NewNoopTracerProvider(), &NoopOtlpClient{}}
+		return &cfdTracer{trace.NewNoopTracerProvider(), &NoopOtlpClient{}, log}
 	}
 	tp := tracesdk.NewTracerProvider(
 		// We want to dump to in-memory exporter immediately
@@ -98,36 +130,43 @@ func NewTracedRequest(req *http.Request) *TracedRequest {
 		)),
 	)
 
-	return &TracedRequest{req.WithContext(ctx), tp, mc}
+	return &cfdTracer{tp, mc, log}
 }
 
-func (cft *TracedRequest) Tracer() trace.Tracer {
+func (cft *cfdTracer) Tracer() trace.Tracer {
 	return cft.TracerProvider.Tracer(tracerInstrumentName)
 }
 
-// Spans returns the spans as base64 encoded protobuf otlp traces.
-func (cft *TracedRequest) AddSpans(headers http.Header, log *zerolog.Logger) {
-	if headers == nil {
-		log.Error().Msgf("provided headers map is nil")
-		return
-	}
-
+// GetSpans returns the spans as base64 encoded string of protobuf otlp traces.
+func (cft *cfdTracer) GetSpans() (enc string) {
 	enc, err := cft.exporter.Spans()
 	switch err {
 	case nil:
 		break
 	case errNoTraces:
-		log.Error().Err(err).Msgf("expected traces to be available")
+		cft.log.Error().Err(err).Msgf("expected traces to be available")
 		return
 	case errNoopTracer:
 		return // noop tracer has no traces
 	default:
-		log.Error().Err(err)
+		cft.log.Error().Err(err)
 		return
 	}
+	return
+}
+
+// AddSpans assigns spans as base64 encoded protobuf otlp traces to provided
+// HTTP headers.
+func (cft *cfdTracer) AddSpans(headers http.Header) {
+	if headers == nil {
+		cft.log.Error().Msgf("provided headers map is nil")
+		return
+	}
+
+	enc := cft.GetSpans()
 	// No need to add header if no traces
 	if enc == "" {
-		log.Error().Msgf("no traces provided and no error from exporter")
+		cft.log.Error().Msgf("no traces provided and no error from exporter")
 		return
 	}
 
@@ -166,6 +205,33 @@ func endSpan(span trace.Span, upstreamStatusCode int, spanStatusCode codes.Code,
 	span.End()
 }
 
+// extractTraceFromString will extract the trace information from the provided
+// propagated trace string context.
+func extractTraceFromString(ctx context.Context, trace string) (context.Context, bool) {
+	if trace == "" {
+		return ctx, false
+	}
+	// Jaeger specific separator
+	parts := strings.Split(trace, separator)
+	if len(parts) != 4 {
+		return ctx, false
+	}
+	if parts[0] == "" {
+		return ctx, false
+	}
+	// Correctly left pad the trace to a length of 32
+	if len(parts[0]) < traceID128bitsWidth {
+		left := traceID128bitsWidth - len(parts[0])
+		parts[0] = strings.Repeat("0", left) + parts[0]
+		trace = strings.Join(parts, separator)
+	}
+
+	// Override the 'cf-trace-id' as 'uber-trace-id' so the jaeger propagator can extract it.
+	traceHeader := map[string]string{TracerContextNameOverride: trace}
+	remoteCtx := otel.GetTextMapPropagator().Extract(ctx, propagation.MapCarrier(traceHeader))
+	return remoteCtx, true
+}
+
 // extractTrace attempts to check for a cf-trace-id from a request and return the
 // trace context with the provided http.Request.
 func extractTrace(req *http.Request) (context.Context, bool) {