Propagate b3 parentspanid and debug flag

packages/opentelemetry-core/src/context/propagation/B3Propagator.ts

@@ -26,9 +26,19 @@ import { getParentSpanContext, setExtractedSpanContext } from '../context';
 export const X_B3_TRACE_ID = 'x-b3-traceid';
 export const X_B3_SPAN_ID = 'x-b3-spanid';
 export const X_B3_SAMPLED = 'x-b3-sampled';
+export const X_B3_PARENT_SPAN_ID = 'x-b3-parentspanid';
+export const X_B3_FLAGS = 'x-b3-flags';
+export const PARENT_SPAN_ID_KEY = Context.createKey(
+  'OpenTelemetry Context Key B3 Parent Span Id'
+);
+export const DEBUG_FLAG_KEY = Context.createKey(
+  'OpenTelemetry Context Key B3 Debug Flag'
+);
 const VALID_TRACEID_REGEX = /^([0-9a-f]{16}){1,2}$/i;
 const VALID_SPANID_REGEX = /^[0-9a-f]{16}$/i;
 const INVALID_ID_REGEX = /^0+$/i;
+const VALID_SAMPLED_VALUES = new Set([true, 'true', 'True', '1', 1]);
+const VALID_UNSAMPLED_VALUES = new Set([false, 'false', 'False', '0', 0]);
 
 function isValidTraceId(traceId: string): boolean {
   return VALID_TRACEID_REGEX.test(traceId) && !INVALID_ID_REGEX.test(traceId);
@@ -38,6 +48,77 @@ function isValidSpanId(spanId: string): boolean {
   return VALID_SPANID_REGEX.test(spanId) && !INVALID_ID_REGEX.test(spanId);
 }
 
+function isValidParentSpanID(spanId: string | undefined): boolean {
+  return spanId === undefined || isValidSpanId(spanId);
+}
+
+function isValidSampledValue(sampled: TraceFlags | undefined): boolean {
+  return sampled === TraceFlags.SAMPLED || sampled === TraceFlags.NONE;
+}
+
+function parseHeader(header: unknown) {
+  return Array.isArray(header) ? header[0] : header;
+}
+
+function getHeaderValue(carrier: unknown, getter: GetterFunction, key: string) {
+  const header = getter(carrier, key);
+  return parseHeader(header);
+}
+
+function getTraceId(carrier: unknown, getter: GetterFunction): string {
+  const traceId = getHeaderValue(carrier, getter, X_B3_TRACE_ID);
+  if (typeof traceId === 'string') {
+    return traceId.padStart(32, '0');
+  }
+  return '';
+}
+
+function getSpanId(carrier: unknown, getter: GetterFunction): string {
+  const spanId = getHeaderValue(carrier, getter, X_B3_SPAN_ID);
+  if (typeof spanId === 'string') {
+    return spanId;
+  }
+  return '';
+}
+
+function getParentSpanId(
+  carrier: unknown,
+  getter: GetterFunction
+): string | undefined {
+  const spanId = getHeaderValue(carrier, getter, X_B3_PARENT_SPAN_ID);
+  if (typeof spanId === 'string') {
+    return spanId;
+  }
+  return;
+}
+
+function getDebug(
+  carrier: unknown,
+  getter: GetterFunction
+): string | undefined {
+  const debug = getHeaderValue(carrier, getter, X_B3_FLAGS);
+  return debug === '1' ? '1' : undefined;
+}
+
+function getTraceFlags(
+  carrier: unknown,
+  getter: GetterFunction
+): TraceFlags | undefined {
+  const traceFlags = getHeaderValue(carrier, getter, X_B3_SAMPLED);
+  const debug = getDebug(carrier, getter);
+  if (debug === '1' || VALID_SAMPLED_VALUES.has(traceFlags)) {
+    return TraceFlags.SAMPLED;
+  }
+  if (VALID_UNSAMPLED_VALUES.has(traceFlags)) {
+    return TraceFlags.NONE;
+  }
+  if (traceFlags === undefined) {
+    return TraceFlags.NONE;
+  }
+  // This indicates to isValidSampledValue that this is not valid
+  return;
+}
+
 /**
  * Propagator for the B3 HTTP header format.
  * Based on: https://github.com/openzipkin/b3-propagation
@@ -46,17 +127,27 @@ export class B3Propagator implements HttpTextPropagator {
   inject(context: Context, carrier: unknown, setter: SetterFunction) {
     const spanContext = getParentSpanContext(context);
     if (!spanContext) return;
-
+    const parentSpanId = context.getValue(PARENT_SPAN_ID_KEY) as
+      | undefined
+      | string;
     if (
       isValidTraceId(spanContext.traceId) &&
-      isValidSpanId(spanContext.spanId)
+      isValidSpanId(spanContext.spanId) &&
+      isValidParentSpanID(parentSpanId)
     ) {
+      const debug = context.getValue(DEBUG_FLAG_KEY);
       setter(carrier, X_B3_TRACE_ID, spanContext.traceId);
       setter(carrier, X_B3_SPAN_ID, spanContext.spanId);
-
-      // We set the header only if there is an existing sampling decision.
-      // Otherwise we will omit it => Absent.
-      if (spanContext.traceFlags !== undefined) {
+      if (parentSpanId) {
+        setter(carrier, X_B3_PARENT_SPAN_ID, parentSpanId);
+      }
+      // According to the B3 spec, if the debug flag is set,
+      // the sampled flag shouldn't be propagated as well.
+      if (debug === '1') {
+        setter(carrier, X_B3_FLAGS, debug);
+      } else if (spanContext.traceFlags !== undefined) {
+        // We set the header only if there is an existing sampling decision.
+        // Otherwise we will omit it => Absent.
         setter(
           carrier,
           X_B3_SAMPLED,
@@ -69,31 +160,25 @@ export class B3Propagator implements HttpTextPropagator {
   }
 
   extract(context: Context, carrier: unknown, getter: GetterFunction): Context {
-    const traceIdHeader = getter(carrier, X_B3_TRACE_ID);
-    const spanIdHeader = getter(carrier, X_B3_SPAN_ID);
-    const sampledHeader = getter(carrier, X_B3_SAMPLED);
-
-    const traceIdHeaderValue = Array.isArray(traceIdHeader)
-      ? traceIdHeader[0]
-      : traceIdHeader;
-    const spanId = Array.isArray(spanIdHeader) ? spanIdHeader[0] : spanIdHeader;
-
-    const options = Array.isArray(sampledHeader)
-      ? sampledHeader[0]
-      : sampledHeader;
-
-    if (typeof traceIdHeaderValue !== 'string' || typeof spanId !== 'string') {
-      return context;
-    }
-
-    const traceId = traceIdHeaderValue.padStart(32, '0');
+    const traceId = getTraceId(carrier, getter);
+    const spanId = getSpanId(carrier, getter);
+    const parentSpanId = getParentSpanId(carrier, getter);
+    const traceFlags = getTraceFlags(carrier, getter) as TraceFlags;
+    const debug = getDebug(carrier, getter);
 
-    if (isValidTraceId(traceId) && isValidSpanId(spanId)) {
+    if (
+      isValidTraceId(traceId) &&
+      isValidSpanId(spanId) &&
+      isValidParentSpanID(parentSpanId) &&
+      isValidSampledValue(traceFlags)
+    ) {
+      context = context.setValue(PARENT_SPAN_ID_KEY, parentSpanId);
+      context = context.setValue(DEBUG_FLAG_KEY, debug);
       return setExtractedSpanContext(context, {
         traceId,
         spanId,
         isRemote: true,
-        traceFlags: isNaN(Number(options)) ? TraceFlags.NONE : Number(options),
+        traceFlags,
       });
     }
     return context;