feat(browser): Report browser.navigation.type on the pageload span

TTFB, FP and FCP are attributes of the pageload span rather than spans
of their own, so unlike LCP, CLS and INP they had no navigation type to
be read against. Report the type web-vitals measured TTFB and FCP on as
an attribute of the pageload span.

Author: logaretm

CHANGELOG.md

@@ -7,6 +7,7 @@
 Work in this release was contributed by @psh4607, @thijsw, @trinitiwowka, @nehaprasad-dev, @JealousGx, @Jxxunnn, @eddie333016, @davidmurdoch, @yashschandra, @atharv-sys32, @AG0708, @birkskyum, @mkly, @mcbbugu, @suhailopensource, @zkasuran, @mohd-akram, @RealBhupesh, @halillusion, @psang39, @hafzism, @JosephDoUrden, @Tyagiquamar, @Andarist, @msnelling, and @oesnuj. Thank you for your contributions!
 
 - feat(browser)!: `browser.navigation.type` on web vital and bfcache navigation spans now carries the navigation type exactly as web-vitals reports it. `bfcache` is now `back-forward-cache`, and a back/forward navigation that missed the bfcache (`back-forward`) or a discarded-tab restore (`restore`) is no longer folded into `navigate`. Update any dashboards or alerts filtering on `bfcache`.
+- feat(browser): The pageload span now carries `browser.navigation.type`, the navigation type web-vitals reported TTFB and FCP for. Those vitals, and FP, are attributes of the pageload span rather than spans of their own, so until now there was no navigation type to read them against.
 - feat(core): Add `createFetchIntegration`, the shared implementation behind the global-`fetch` integrations in `@sentry/bun`, `@sentry/cloudflare`, `@sentry/deno` and `@sentry/vercel-edge`. Those four packages carried four copies of it; they now share one. Two changes come out of that:
   - All four gain a `tracePropagation` option (default `true`). Turn it off to stop injecting `sentry-trace` and `baggage` without also turning off spans. To scope propagation to specific URLs, keep using `tracePropagationTargets` in the client options.
   - Integration options now follow the client. Previously a second `Sentry.init()` in the same process silently reused the options of the first one.

dev-packages/browser-integration-tests/suites/tracing/browserTracingIntegration/pageload-streamed/test.ts

@@ -8,6 +8,7 @@ import {
   SEMANTIC_ATTRIBUTE_SENTRY_SDK_INTEGRATIONS,
 } from '@sentry/core';
 import {
+  BROWSER_NAVIGATION_TYPE,
   SENTRY_SEGMENT_NAME_SOURCE,
   SENTRY_SEGMENT_ID,
   SENTRY_SEGMENT_NAME,
@@ -125,6 +126,10 @@ sentryTest(
             type: expect.stringMatching(/^(integer)|(double)$/),
             value: expect.any(Number),
           },
+          [BROWSER_NAVIGATION_TYPE]: {
+            type: 'string',
+            value: 'navigate',
+          },
         }),
         'sentry.idle_span_finish_reason': {
           type: 'string',

packages/browser-utils/src/web-vitals/tracking.ts

@@ -1,8 +1,9 @@
 import type { Client, Measurements, Span } from '@sentry/core';
 import { browserPerformanceTimeOrigin, debug, setMeasurement, spanToJSON } from '@sentry/core';
-import { SENTRY_OP } from '@sentry/conventions/attributes';
+import { BROWSER_NAVIGATION_TYPE, SENTRY_OP } from '@sentry/conventions/attributes';
 import { DEBUG_BUILD } from '../debug-build';
 import { htmlTreeAsString } from '../htmlTreeAsString';
+import type { MetricNavigationType } from '../instrumentation/performanceObserver';
 import {
   addClsInstrumentationHandler,
   addFcpInstrumentationHandler,
@@ -17,6 +18,7 @@ import { getActivationStart, getNavigationEntry, getVisibilityWatcher } from './
 let _measurements: Measurements = {};
 let _lcpEntry: LargestContentfulPaint | undefined;
 let _clsEntry: LayoutShift | undefined;
+let _navigationType: MetricNavigationType | undefined;
 
 interface StartTrackingWebVitalsOptions {
   trackCls: boolean;
@@ -83,6 +85,8 @@ function _trackLCP(): () => void {
 
 function _trackTtfb(): () => void {
   return addTtfbInstrumentationHandler(({ metric }) => {
+    _navigationType = metric.navigationType;
+
     const entry = metric.entries[metric.entries.length - 1];
     if (!entry) {
       return;
@@ -95,6 +99,7 @@ function _trackTtfb(): () => void {
 /** Starts tracking the First Contentful Paint on the current page. */
 function _trackFcp(): () => void {
   return addFcpInstrumentationHandler(({ metric }) => {
+    _navigationType = metric.navigationType;
     _measurements['fcp'] = { value: metric.value, unit: 'millisecond' };
   });
 }
@@ -201,6 +206,12 @@ export function addWebVitalsToSpan(span: Span, options: AddWebVitalsToSpanOption
       _setWebVitalAttributes(span, options);
     }
 
+    // TTFB, FP and FCP are attributes of this span rather than spans of their own, so the navigation
+    // type they were measured on is reported here for them to be read against.
+    if (_navigationType) {
+      span.setAttribute(BROWSER_NAVIGATION_TYPE, _navigationType);
+    }
+
     // Set timeOrigin which denotes the timestamp which to base the LCP/FCP/FP/TTFB measurements on
     span.setAttribute(spanStreamingEnabled ? 'browser.performance.time_origin' : 'performance.timeOrigin', timeOrigin);
 
@@ -222,6 +233,7 @@ export function addWebVitalsToSpan(span: Span, options: AddWebVitalsToSpanOption
 function resetWebVitalState(): void {
   _lcpEntry = undefined;
   _clsEntry = undefined;
+  _navigationType = undefined;
   _measurements = {};
 }
 

packages/browser-utils/test/web-vitals/tracking-fp-fcp-prerender.test.ts

@@ -124,5 +124,6 @@ describe('startTrackingWebVitals', () => {
 
     expect(spanToJSON(pageloadSpan).attributes['browser.web_vital.fp.value']).toBe(12);
     expect(spanToJSON(pageloadSpan).attributes['browser.web_vital.fcp.value']).toBe(18);
+    expect(spanToJSON(pageloadSpan).attributes['browser.navigation.type']).toBe('prerender');
   });
 });

packages/browser-utils/test/web-vitals/tracking-fp-fcp.test.ts

@@ -90,5 +90,6 @@ describe('startTrackingWebVitals', () => {
 
     expect(spanToJSON(pageloadSpan).attributes['browser.web_vital.fp.value']).toBe(12);
     expect(spanToJSON(pageloadSpan).attributes['browser.web_vital.fcp.value']).toBe(18);
+    expect(spanToJSON(pageloadSpan).attributes['browser.navigation.type']).toBe('navigate');
   });
 });