Add tests for tracesSampleRate behavior

Author: Luca Forstner

dev-packages/node-integration-tests/src/index.ts

@@ -29,6 +29,9 @@ export function startExpressServerAndSendPortToRunner(app: Express, port: number
   const server = app.listen(port || 0, () => {
     const address = server.address() as AddressInfo;
 
+    // @ts-expect-error If we write the port to the app we can read it within route handlers in tests
+    app.port = port || address.port;
+
     // eslint-disable-next-line no-console
     console.log(`{"port":${port || address.port}}`);
   });
@@ -41,3 +44,11 @@ export function sendPortToRunner(port: number): void {
   // eslint-disable-next-line no-console
   console.log(`{"port":${port}}`);
 }
+
+/**
+ * Can be used to get the port of a running app, so requests can be sent to a server from within the server.
+ */
+export function getPortAppIsRunningOn(app: Express): number | undefined {
+  // @ts-expect-error It's not defined in the types but we'd like to read it.
+  return app.port;
+}

dev-packages/node-integration-tests/suites/sample-rand-propagation/tracesSampleRate/server.js

@@ -0,0 +1,40 @@
+const { loggingTransport } = require('@sentry-internal/node-integration-tests');
+const Sentry = require('@sentry/node');
+
+Sentry.init({
+  dsn: 'https://[email protected]/1337',
+  transport: loggingTransport,
+  tracesSampleRate: 1,
+});
+
+// express must be required after Sentry is initialized
+const express = require('express');
+const cors = require('cors');
+const {
+  startExpressServerAndSendPortToRunner,
+  getPortAppIsRunningOn,
+} = require('@sentry-internal/node-integration-tests');
+
+const app = express();
+
+app.use(cors());
+
+app.get('/check', (req, res) => {
+  const appPort = getPortAppIsRunningOn(app);
+  // eslint-disable-next-line no-undef
+  fetch(`http://localhost:${appPort}/bounce`)
+    .then(r => r.json())
+    .then(bounceRes => {
+      res.json({ propagatedData: bounceRes });
+    });
+});
+
+app.get('/bounce', (req, res) => {
+  res.json({
+    baggage: req.headers['baggage'],
+  });
+});
+
+Sentry.setupExpressErrorHandler(app);
+
+startExpressServerAndSendPortToRunner(app);

dev-packages/node-integration-tests/suites/sample-rand-propagation/tracesSampleRate/test.ts

@@ -0,0 +1,91 @@
+import { cleanupChildProcesses, createRunner } from '../../../utils/runner';
+
+describe('sample_rand propagation (default)', () => {
+  afterAll(() => {
+    cleanupChildProcesses();
+  });
+
+  test('propagates a sample rand when there are no incoming trace headers', async () => {
+    const runner = createRunner(__dirname, 'server.js').start();
+    const response = await runner.makeRequest('get', '/check');
+    expect(response).toEqual({
+      propagatedData: {
+        baggage: expect.stringMatching(/sentry-sample_rand=0\.[0-9]+/),
+      },
+    });
+  });
+
+  test('propagates a sample rand when there is a sentry-trace header and incoming sentry baggage', async () => {
+    const runner = createRunner(__dirname, 'server.js').start();
+    const response = await runner.makeRequest('get', '/check', {
+      headers: {
+        'sentry-trace': '530699e319cc067ce440315d74acb312-414dc2a08d5d1dac-1',
+        baggage: 'sentry-release=foo,sentry-sample_rand=0.424242',
+      },
+    });
+    expect(response).toEqual({
+      propagatedData: {
+        baggage: expect.stringMatching(/sentry-sample_rand=0\.424242/),
+      },
+    });
+  });
+
+  test('propagates a sample rand when there is an incoming sentry-trace header but no baggage header', async () => {
+    const runner = createRunner(__dirname, 'server.js').start();
+    const response = await runner.makeRequest('get', '/check', {
+      headers: {
+        'sentry-trace': '530699e319cc067ce440315d74acb312-414dc2a08d5d1dac-1',
+      },
+    });
+    expect(response).toEqual({
+      propagatedData: {
+        baggage: expect.stringMatching(/sentry-sample_rand=0\.[0-9]+/),
+      },
+    });
+  });
+
+  test('propagates a sample_rand that would lead to a positive sampling decision when there is an incoming positive sampling decision but no sample_rand in the baggage header', async () => {
+    const runner = createRunner(__dirname, 'server.js').start();
+    const response = await runner.makeRequest('get', '/check', {
+      headers: {
+        'sentry-trace': '530699e319cc067ce440315d74acb312-414dc2a08d5d1dac-1',
+        baggage: 'sentry-sample_rate=0.25',
+      },
+    });
+
+    const sampleRand = Number((response as any).propagatedData.baggage.match(/sentry-sample_rand=(0\.[0-9]+)/)[1]);
+
+    expect(sampleRand).toStrictEqual(expect.any(Number));
+    expect(sampleRand).not.toBeNaN();
+    expect(sampleRand).toBeLessThan(0.25);
+  });
+
+  test('propagates a sample_rand that would lead to a negative sampling decision when there is an incoming negative sampling decision but no sample_rand in the baggage header', async () => {
+    const runner = createRunner(__dirname, 'server.js').start();
+    const response = await runner.makeRequest('get', '/check', {
+      headers: {
+        'sentry-trace': '530699e319cc067ce440315d74acb312-414dc2a08d5d1dac-0',
+        baggage: 'sentry-sample_rate=0.75',
+      },
+    });
+
+    const sampleRand = Number((response as any).propagatedData.baggage.match(/sentry-sample_rand=(0\.[0-9]+)/)[1]);
+
+    expect(sampleRand).toStrictEqual(expect.any(Number));
+    expect(sampleRand).not.toBeNaN();
+    expect(sampleRand).toBeGreaterThanOrEqual(0.75);
+  });
+
+  test('a new sample_rand when there is no sentry-trace header but a baggage header with sample_rand', async () => {
+    const runner = createRunner(__dirname, 'server.js').start();
+    const response = await runner.makeRequest('get', '/check', {
+      headers: {
+        baggage: 'sentry-sample_rate=0.75,sentry-sample_rand=0.5',
+      },
+    });
+
+    expect((response as any).propagatedData.baggage).toMatch(/sentry-sample_rand=0\.[0-9]+/);
+    const sampleRandStr = (response as any).propagatedData.baggage.match(/sentry-sample_rand=(0\.[0-9]+)/)[1];
+    expect(sampleRandStr).not.toBe('0.5');
+  });
+});