feat(@opentelemetry-instrumentation-fetch): optionally ignore network events (#3028)

Co-authored-by: Valentin Marchaud <contact@vmarchaud.fr>

Author: gregolsen

experimental/CHANGELOG.md

@@ -10,6 +10,7 @@ All notable changes to experimental packages in this project will be documented
 
 ### :rocket: (Enhancement)
 
+* feat(opentelemetry-instrumentation-fetch): optionally ignore network events #3028 @gregolsen
 * feat(http-instrumentation): record exceptions in http instrumentation #3008 @luismiramirez
 
 ### :bug: (Bug Fix)

experimental/packages/opentelemetry-instrumentation-fetch/README.md

@@ -62,9 +62,10 @@ See [examples/tracer-web/fetch](https://github.com/open-telemetry/opentelemetry-
 
 Fetch instrumentation plugin has few options available to choose from. You can set the following:
 
-| Options                                                                                                                                           | Type                          | Description                           |
-| ------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------- | ------------------------------------- |
-| [`applyCustomAttributesOnSpan`](https://github.com/open-telemetry/opentelemetry-js/blob/main/experimental/packages/opentelemetry-instrumentation-fetch/src/fetch.ts#L64) | `HttpCustomAttributeFunction` | Function for adding custom attributes |
+| Options                                                                                                                                                                  | Type                          | Description                                                                             |
+|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------|-----------------------------------------------------------------------------------------|
+| [`applyCustomAttributesOnSpan`](https://github.com/open-telemetry/opentelemetry-js/blob/main/experimental/packages/opentelemetry-instrumentation-fetch/src/fetch.ts#L64) | `HttpCustomAttributeFunction` | Function for adding custom attributes                                                   |
+| [`ignoreNetworkEvents`](https://github.com/open-telemetry/opentelemetry-js/blob/main/experimental/packages/opentelemetry-instrumentation-fetch/src/fetch.ts#L67)                      | `boolean`                     | Disable network events being added as span events (network events are added by default) |
 
 ## Useful links
 

experimental/packages/opentelemetry-instrumentation-fetch/src/fetch.ts

@@ -63,6 +63,8 @@ export interface FetchInstrumentationConfig extends InstrumentationConfig {
   ignoreUrls?: Array<string | RegExp>;
   /** Function for adding custom attributes on the span */
   applyCustomAttributesOnSpan?: FetchCustomAttributeFunction;
+  // Ignore adding network events as span events
+  ignoreNetworkEvents?: boolean;
 }
 
 /**
@@ -105,7 +107,9 @@ export class FetchInstrumentation extends InstrumentationBase<Promise<Response>>
       },
       api.trace.setSpan(api.context.active(), span)
     );
-    web.addSpanNetworkEvents(childSpan, corsPreFlightRequest);
+    if (!this._getConfig().ignoreNetworkEvents) {
+      web.addSpanNetworkEvents(childSpan, corsPreFlightRequest);
+    }
     childSpan.end(
       corsPreFlightRequest[web.PerformanceTimingNames.RESPONSE_END]
     );
@@ -247,7 +251,9 @@ export class FetchInstrumentation extends InstrumentationBase<Promise<Response>>
         this._addChildSpan(span, corsPreFlightRequest);
         this._markResourceAsUsed(corsPreFlightRequest);
       }
-      web.addSpanNetworkEvents(span, mainRequest);
+      if (!this._getConfig().ignoreNetworkEvents) {
+        web.addSpanNetworkEvents(span, mainRequest);
+      }
     }
   }
 

experimental/packages/opentelemetry-instrumentation-fetch/test/fetch.test.ts

@@ -900,4 +900,20 @@ describe('fetch', () => {
       );
     });
   });
+
+  describe('when network events are ignored', () => {
+    beforeEach(async () => {
+      await prepareData(url, {
+        ignoreNetworkEvents: true,
+      });
+    });
+    afterEach(() => {
+      clearData();
+    });
+    it('should NOT add network events', () => {
+      const span: tracing.ReadableSpan = exportSpy.args[1][0][0];
+      const events = span.events;
+      assert.strictEqual(events.length, 0, 'number of events is wrong');
+    });
+  });
 });