Separate context propagation (OTEP 66) (open-telemetry#769)

* feat: separate context propagation

api/package.json

@@ -45,6 +45,9 @@
   "publishConfig": {
     "access": "public"
   },
+  "dependencies": {
+    "@opentelemetry/scope-base": "^0.4.0"
+  },
   "devDependencies": {
     "@types/mocha": "^5.2.7",
     "@types/node": "^12.6.8",

api/src/context/propagation/HttpTextFormat.ts

@@ -14,40 +14,35 @@
  * limitations under the License.
  */
 
-import { SpanContext } from '../../trace/span_context';
+import { Context } from '@opentelemetry/scope-base';
 import { Carrier } from './carrier';
 
 /**
- * Injects and extracts a value as text into carriers that travel in-band
- * across process boundaries. Encoding is expected to conform to the HTTP
+ * Injects {@link Context} into and extracts it from carriers that travel
+ * in-band across process boundaries. Encoding is expected to conform to the HTTP
  * Header Field semantics. Values are often encoded as RPC/HTTP request headers.
  *
  * The carrier of propagated data on both the client (injector) and server
- * (extractor) side is usually an http request. Propagation is usually
- * implemented via library- specific request interceptors, where the
- * client-side injects values and the server-side extracts them.
+ * (extractor) side is usually an object such as http headers.
  */
 export interface HttpTextFormat {
   /**
-   * Injects the given {@link SpanContext} instance to transmit over the wire.
+   * Injects values from a given {@link Context} into a carrier.
    *
    * OpenTelemetry defines a common set of format values (BinaryFormat and
    * HTTPTextFormat), and each has an expected `carrier` type.
    *
-   * @param spanContext the SpanContext to transmit over the wire.
-   * @param format the format of the carrier.
+   * @param context the Context from which to extract values to transmit over the wire.
    * @param carrier the carrier of propagation fields, such as http request headers.
    */
-  inject(spanContext: SpanContext, format: string, carrier: Carrier): void;
+  inject(context: Context, carrier: Carrier): void;
 
   /**
-   * Returns a {@link SpanContext} instance extracted from `carrier` in the
-   * given format from upstream.
+   * Given a {@link Context} and a carrier, extract context values from a carrier and
+   * return a new context, created from the old context, with the extracted values.
    *
-   * @param format the format of the carrier.
+   * @param context the Context from which to extract values to transmit over the wire.
    * @param carrier the carrier of propagation fields, such as http request headers.
-   * @returns SpanContext The extracted SpanContext, or null if no such
-   *     SpanContext could be found in carrier.
    */
-  extract(format: string, carrier: Carrier): SpanContext | null;
+  extract(context: Context, carrier: Carrier): Context;
 }

api/src/context/propagation/NoopHttpTextFormat.ts

@@ -14,19 +14,19 @@
  * limitations under the License.
  */
 
-import { SpanContext } from '../../trace/span_context';
+import { Context } from '@opentelemetry/scope-base';
 import { Carrier } from './carrier';
 import { HttpTextFormat } from './HttpTextFormat';
 
 /**
  * No-op implementations of {@link HttpTextFormat}.
  */
 export class NoopHttpTextFormat implements HttpTextFormat {
-  // By default does nothing
-  inject(spanContext: SpanContext, format: string, carrier: Carrier): void {}
-  // By default does nothing
-  extract(format: string, carrier: Carrier): SpanContext | null {
-    return null;
+  /** Noop inject function does nothing */
+  inject(context: Context, carrier: Carrier): void {}
+  /** Noop extract function does nothing and returns the input context */
+  extract(context: Context, carrier: Carrier): Context {
+    return context;
   }
 }
 

api/src/index.ts

@@ -46,6 +46,8 @@ export * from './trace/NoopTracerProvider';
 export * from './metrics/NoopMeterProvider';
 export * from './metrics/NoopMeter';
 
+export { Context } from '@opentelemetry/scope-base';
+
 import { TraceAPI } from './api/trace';
 /** Entrypoint for trace API */
 export const trace = TraceAPI.getInstance();

api/test/noop-implementations/noop-tracer.test.ts

@@ -16,6 +16,7 @@
 
 import * as assert from 'assert';
 import { NoopTracer, NOOP_SPAN, SpanKind } from '../../src';
+import { Context } from '@opentelemetry/scope-base';
 
 describe('NoopTracer', () => {
   it('should not crash', () => {
@@ -38,8 +39,12 @@ describe('NoopTracer', () => {
     assert.deepStrictEqual(tracer.getCurrentSpan(), NOOP_SPAN);
     const httpTextFormat = tracer.getHttpTextFormat();
     assert.ok(httpTextFormat);
-    httpTextFormat.inject(spanContext, 'HttpTextFormat', {});
-    assert.deepStrictEqual(httpTextFormat.extract('HttpTextFormat', {}), null);
+
+    httpTextFormat.inject(Context.ROOT_CONTEXT, {});
+    assert.deepStrictEqual(
+      httpTextFormat.extract(Context.ROOT_CONTEXT, {}),
+      Context.ROOT_CONTEXT
+    );
 
     const binaryFormat = tracer.getBinaryFormat();
     assert.ok(binaryFormat);