add method to generate outgoing trace headers

Author: lobsterkatie

packages/tracing/src/span.ts

@@ -1,5 +1,5 @@
 /* eslint-disable max-lines */
-import { Primitive, Span as SpanInterface, SpanContext, Transaction } from '@sentry/types';
+import { Primitive, Span as SpanInterface, SpanContext, TraceHeaders, Transaction } from '@sentry/types';
 import { dropUndefinedKeys, timestampWithMs, uuid4 } from '@sentry/utils';
 
 import { SpanStatus } from './spanstatus';
@@ -284,6 +284,19 @@ export class Span implements SpanInterface {
     return this;
   }
 
+  /**
+   * @inheritDoc
+   */
+  public getTraceHeaders(): TraceHeaders {
+    // tracestates live on the transaction, so if this is a free-floating span, there won't be one
+    const tracestate = this.transaction && `sentry=${this.transaction.tracestate}`; // TODO kmclb
+
+    return {
+      'sentry-trace': this.toTraceparent(),
+      ...(tracestate && { tracestate }),
+    };
+  }
+
   /**
    * @inheritDoc
    */

packages/tracing/test/span.test.ts

@@ -101,6 +101,26 @@ describe('Span', () => {
     });
   });
 
+  describe('getTraceHeaders', () => {
+    it('returns correct headers', () => {
+      const hub = new Hub(
+        new BrowserClient({
+          dsn: 'https://[email protected]/12312012',
+          tracesSampleRate: 1,
+          release: 'off.leash.park',
+          environment: 'dogpark',
+        }),
+      );
+      const transaction = hub.startTransaction({ name: 'FETCH /ball' });
+      const span = transaction.startChild({ op: 'dig.hole' });
+
+      const headers = span.getTraceHeaders();
+
+      expect(headers['sentry-trace']).toEqual(span.toTraceparent());
+      expect(headers.tracestate).toEqual(`sentry=${transaction.tracestate}`);
+    });
+  });
+
   describe('toJSON', () => {
     test('simple', () => {
       const span = JSON.parse(

packages/types/src/index.ts

@@ -23,7 +23,7 @@ export { SdkInfo } from './sdkinfo';
 export { SdkMetadata } from './sdkmetadata';
 export { Session, SessionContext, SessionStatus } from './session';
 export { Severity } from './severity';
-export { Span, SpanContext } from './span';
+export { Span, SpanContext, TraceHeaders } from './span';
 export { StackFrame } from './stackframe';
 export { Stacktrace } from './stacktrace';
 export { Status } from './status';

packages/types/src/span.ts

@@ -158,6 +158,13 @@ export interface Span extends SpanContext {
   /** Updates the current span with a new `SpanContext` */
   updateWithContext(spanContext: SpanContext): this;
 
+  /**
+   * Get headers to attach to any outgoing requests made by the operation corresponding to the current span
+   *
+   * @returns An object containing the headers
+   */
+  getTraceHeaders(): TraceHeaders;
+
   /** Convert the object to JSON for w. spans array info only */
   getTraceContext(): {
     data?: { [key: string]: any };
@@ -169,6 +176,7 @@ export interface Span extends SpanContext {
     tags?: { [key: string]: Primitive };
     trace_id: string;
   };
+
   /** Convert the object to JSON */
   toJSON(): {
     data?: { [key: string]: any };
@@ -183,3 +191,8 @@ export interface Span extends SpanContext {
     trace_id: string;
   };
 }
+
+export type TraceHeaders = {
+  'sentry-trace': string;
+  tracestate?: string;
+};