fix(tracing): Skip native frames and stall tracking for unsampled spans

packages/core/src/js/tracing/integrations/nativeFrames.ts

@@ -1,5 +1,5 @@
 import type { Client, Event, Integration, Measurements, MeasurementUnit, Span } from '@sentry/core';
-import { debug, getRootSpan, spanToJSON, timestampInSeconds } from '@sentry/core';
+import { debug, getRootSpan, spanIsSampled, spanToJSON, timestampInSeconds } from '@sentry/core';
 import type { NativeFramesResponse } from '../../NativeRNSentry';
 import { AsyncExpiringMap } from '../../utils/AsyncExpiringMap';
 import { isRootSpan } from '../../utils/span';
@@ -86,6 +86,10 @@ export const nativeFramesIntegration = (): Integration => {
   };
 
   const fetchStartFramesForSpan = (span: Span): void => {
+    if (!spanIsSampled(span)) {
+      return;
+    }
+
     const spanId = span.spanContext().spanId;
     const spanType = isRootSpan(span) ? 'root' : 'child';
     debug.log(`[${INTEGRATION_NAME}] Fetching frames for ${spanType} span start (${spanId}).`);

packages/core/src/js/tracing/integrations/stalltracking.ts

@@ -1,6 +1,6 @@
 /* eslint-disable max-lines */
 import type { Client, Integration, Measurements, MeasurementUnit, Span } from '@sentry/core';
-import { debug, getRootSpan, spanToJSON, timestampInSeconds } from '@sentry/core';
+import { debug, getRootSpan, spanIsSampled, spanToJSON, timestampInSeconds } from '@sentry/core';
 import type { AppStateStatus } from 'react-native';
 import { AppState } from 'react-native';
 import { STALL_COUNT, STALL_LONGEST_TIME, STALL_TOTAL_TIME } from '../../measurements';
@@ -123,6 +123,10 @@ export const stallTrackingIntegration = ({
       return;
     }
 
+    if (!spanIsSampled(rootSpan)) {
+      return;
+    }
+
     if (statsByRootSpan.has(rootSpan)) {
       debug.error(
         '[StallTracking] Tried to start stall tracking on a transaction already being tracked. Measurements might be lost.',

packages/core/test/tracing/integrations/nativeframes.test.ts

@@ -520,4 +520,31 @@ describe('NativeFramesInstrumentation', () => {
       }),
     );
   });
+
+  describe('unsampled spans', () => {
+    beforeEach(() => {
+      global.Date.now = jest.fn(() => mockDate.getTime());
+
+      getCurrentScope().clear();
+      getIsolationScope().clear();
+      getGlobalScope().clear();
+
+      const options = getDefaultTestClientOptions({
+        tracesSampleRate: 0,
+        enableNativeFramesTracking: true,
+        integrations: [nativeFramesIntegration()],
+      });
+      client = new TestClient(options);
+      setCurrentClient(client);
+      client.init();
+    });
+
+    it('does not fetch native frames for unsampled spans', () => {
+      startSpan({ name: 'unsampled transaction', forceTransaction: true }, () => {
+        // span starts and ends — no work expected
+      });
+
+      expect(NATIVE.fetchNativeFrames).not.toHaveBeenCalled();
+    });
+  });
 });

packages/core/test/tracing/integrations/stallTracking/stalltracking.test.ts

@@ -225,4 +225,31 @@ describe('StallTracking', () => {
 
     expect(client.eventQueue[0].measurements).toBeUndefined();
   });
+
+  it('does not track stalls for unsampled spans', async () => {
+    getCurrentScope().clear();
+    getIsolationScope().clear();
+    getGlobalScope().clear();
+
+    const unsampledOptions = getDefaultTestClientOptions({
+      tracesSampleRate: 0,
+      enableStallTracking: true,
+      integrations: [stallTrackingIntegration()],
+      enableAppStartTracking: false,
+    });
+    const unsampledClient = new TestClient(unsampledOptions);
+    setCurrentClient(unsampledClient);
+    unsampledClient.init();
+
+    startSpan({ name: 'unsampled transaction', forceTransaction: true }, () => {
+      expensiveOperation();
+      jest.runOnlyPendingTimers();
+    });
+
+    await unsampledClient.flush();
+
+    // Event is either not sent or has no stall measurements
+    const event = unsampledClient.eventQueue[0];
+    expect(event?.measurements?.stall_count).toBeUndefined();
+  });
 });