feat: add jaeger http trace format (open-telemetry#696)

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

@@ -14,34 +14,22 @@
  * limitations under the License.
  */
 
-import { SpanContext, HttpTextFormat, TraceFlags } from '@opentelemetry/types';
+import { SpanContext, HttpTextFormat, TraceFlags } from "@opentelemetry/types";
 
-export const UBER_TRACE_ID_HEADER = 'uber-trace-id';
+export const UBER_TRACE_ID_HEADER = "uber-trace-id";
 
 /**
  * Propagates {@link SpanContext} through Trace Context format propagation.
  * {trace-id}:{span-id}:{parent-span-id}:{flags}
  * {trace-id}
  * 64-bit or 128-bit random number in base16 format
  * Can be variable length, shorter values are 0-padded on the left
- * Clients in some languages support 128-bit, migration pending
  * Value of 0 is invalid
  * {span-id}
  * 64-bit random number in base16 format
- * {parent-span-id}
- * 64-bit value in base16 format representing parent span id
- * Deprecated, most Jaeger clients ignore on the receiving side, but still include it on the sending side
- * 0 value is valid and means “root span” (when not ignored)
+ * {parent-span-id} set to 0 because this field is deprecated
  * {flags}
  * One byte bitmap, as two hex digits
- * Bit 1 (right-most, least significant) is “sampled” flag
- * 1 means the trace is sampled and all downstream services are advised to respect that
- * 0 means the trace is not sampled and all downstream services are advised to respect that
- * We’re considering a new feature that allows downstream services to upsample if they find their tracing level is too low
- * Bit 2 is “debug” flag
- * Debug flag should only be set when the sampled flag is set
- * Instructs the backend to try really hard not to drop this trace
- * Other bits are unused.
  * Inspired by jaeger-client-node project
  */
 export class JaegerHttpTraceFormat implements HttpTextFormat {
@@ -52,12 +40,9 @@ export class JaegerHttpTraceFormat implements HttpTextFormat {
   ) {
     const hexTraceId = removeLeadingZeros(spanContext.traceId);
     const hexSpanId = removeLeadingZeros(spanContext.spanId);
-    const parentSpanId = '0';
     const flags = TraceFlags.SAMPLED;
 
-    carrier[
-      UBER_TRACE_ID_HEADER
-    ] = `${hexTraceId}:${hexSpanId}:${parentSpanId}:${flags}`;
+    carrier[UBER_TRACE_ID_HEADER] = `${hexTraceId}:${hexSpanId}:0:${flags}`;
   }
 
   extract(
@@ -79,34 +64,21 @@ export class JaegerHttpTraceFormat implements HttpTextFormat {
  * @return {string} - returns the input string without leading zeros.
  **/
 function removeLeadingZeros(input: string): string {
-  let counter = 0;
-  let length = input.length - 1;
-  for (let i = 0; i < length; i++) {
-    if (input.charAt(i) === '0') {
-      counter++;
-    } else {
-      break;
-    }
-  }
-
-  return input.substring(counter);
+  return input.replace(/^0+/, "");
 }
 
 /**
  * @param {string} serializedString - a serialized span context.
  * @return {SpanContext} - returns a span context represented by the serializedString.
  **/
 function deserializeSpanContext(serializedString: string): SpanContext | null {
-  let headers = serializedString.split(':');
+  let headers = serializedString.split(":");
   if (headers.length !== 4) {
     return null;
   }
   const [traceId, spanId, , flags] = headers;
 
-  const traceFlags =
-    Number('0x' + (isNaN(Number(flags)) ? 1 : Number(flags))) & 1;
-
-  const isRemote = true;
+  const traceFlags = flags.match(/^[0-9a-f]{2}$/i) ? parseInt(flags) & 1 : 1;
 
-  return { traceId, spanId, isRemote, traceFlags };
+  return { traceId, spanId, isRemote: true, traceFlags };
 }