task(settings): Target sentry tracing to capture metrics for index

packages/fxa-settings/src/index.tsx

@@ -48,6 +48,16 @@ try {
     release: config.version,
     sentry: {
       ...config.sentry,
+      tracesSampler: (context) => {
+        let rate = 0;
+        // We only want to sample the index page for now.
+        if (context.name === '/') {
+          if (typeof config.sentry.tracesSampleRate === 'number') {
+            rate = config.sentry.tracesSampleRate;
+          }
+        }
+        return rate;
+      },
     },
   });
 

packages/fxa-settings/src/lib/config.ts

@@ -23,6 +23,7 @@ export interface Config {
     dsn: string;
     env: string;
     sampleRate: number;
+    tracesSampleRate: number;
     serverName: string;
     clientName: string;
     version: string;

packages/fxa-shared/sentry/browser.ts

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 import * as Sentry from '@sentry/browser';
+import { SamplingContext } from '@sentry/core';
 import { SentryConfigOpts } from './models/SentryConfigOpts';
 import { ILogger } from '../log';
 import { tagFxaName } from './tag';
@@ -167,12 +168,20 @@ function configure(config: SentryConfigOpts, log?: ILogger) {
   disable();
 
   const opts = buildSentryConfig(config, log);
+
+  // If tracing is configured, add the integration.
+  const integrations = [];
+  if (opts.tracesSampleRate || opts.tracesSampler) {
+    integrations.push(Sentry.browserTracingIntegration())
+  }
+
   try {
     Sentry.init({
       ...opts,
       beforeSend: function (event: Sentry.ErrorEvent, hint?: Sentry.EventHint) {
         return beforeSend(opts, event, hint);
       },
+      integrations,
     });
   } catch (e) {
     log.error(e);

packages/fxa-shared/sentry/config-builder.ts

@@ -36,6 +36,7 @@ export function buildSentryConfig(config: SentryConfigOpts, log: ILogger) {
     serverName: config.sentry?.serverName,
     fxaName: config.sentry?.clientName || config.sentry?.serverName,
     tracesSampleRate: config.sentry?.tracesSampleRate,
+    tracesSampler: config.sentry?.tracesSampler,
   };
 
   return opts;

packages/fxa-shared/sentry/models/SentryConfigOpts.ts

@@ -1,6 +1,7 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+import { SamplingContext } from '@sentry/core';
 
 export type SentryConfigOpts = {
   /** Name of release */
@@ -27,5 +28,8 @@ export type SentryConfigOpts = {
 
     /** The tracing sample rate. Setting this above 0 will aso result in performance metrics being captured. */
     tracesSampleRate?: number;
+
+    /** Call back to dynamically determine sampling rate. When defined, tracesSampleRate won't be used. */
+    tracesSampler?: (context: SamplingContext) => number | boolean;
   };
 };