[WIP] feat: Span Streaming POC

[Lms24]

This PR contains the POC span streaming implementation for browser SDKs.

Can be tested on @sentry/browser@10.21.0-alpha.1 and any higher-level SDKs.

To opt into span streaming, set:

Sentry.init({
  dsn: '...',
  tracesSampleRate: 1,
  traceLifecycle: 'stream', <-- 
  integrations: [
    Sentry.browserTracingIntegration();
    Sentry.spanStreamingIntegration(); <-- 
  ],

  // if you use beforeSendSpan, you have to opt into the new serialized span format:
  beforeSendSpan: withStreamSpan(serializedSpan => {
     // do something
     return serializedSpan
   }),
})

Also note that spans will no longer be sent to any event processors added via one if the *.addEventProcessor APIs. If you have any event processors, consider using beforeSendSpan or ignoreSpans.

[github-actions]

size-limit report 📦

Path	Size	% Change	Change
⛔️ @sentry/browser (max: 25 kB)	25.65 kB	+3.42%	+846 B 🔺
⛔️ @sentry/browser - with treeshaking flags (max: 24.1 kB)	24.19 kB	+3.82%	+888 B 🔺
⛔️ @sentry/browser (incl. Tracing) (max: 42 kB)	42.6 kB	+2.55%	+1.06 kB 🔺
@sentry/browser (incl. Tracing, Profiling)	47.18 kB	+2.26%	+1.04 kB 🔺
@sentry/browser (incl. Tracing, Replay)	81.13 kB	+1.46%	+1.16 kB 🔺
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	70.72 kB	+1.47%	+1.02 kB 🔺
@sentry/browser (incl. Tracing, Replay with Canvas)	85.8 kB	+1.37%	+1.15 kB 🔺
@sentry/browser (incl. Tracing, Replay, Feedback)	97.99 kB	+1.15%	+1.11 kB 🔺
⛔️ @sentry/browser (incl. Feedback) (max: 42 kB)	42.35 kB	+2.01%	+831 B 🔺
@sentry/browser (incl. sendFeedback)	30.31 kB	+2.79%	+821 B 🔺
⛔️ @sentry/browser (incl. FeedbackAsync) (max: 35 kB)	35.33 kB	+2.45%	+844 B 🔺
⛔️ @sentry/react (max: 27 kB)	27.38 kB	+3.23%	+856 B 🔺
@sentry/react (incl. Tracing)	44.86 kB	+2.53%	+1.1 kB 🔺
@sentry/vue	30.29 kB	+3.49%	+1.02 kB 🔺
⛔️ @sentry/vue (incl. Tracing) (max: 44 kB)	44.43 kB	+2.47%	+1.07 kB 🔺
⛔️ @sentry/svelte (max: 25 kB)	25.68 kB	+3.45%	+856 B 🔺
⛔️ CDN Bundle (max: 27.5 kB)	27.98 kB	+2.73%	+743 B 🔺
⛔️ CDN Bundle (incl. Tracing) (max: 43 kB)	43.22 kB	+2.35%	+992 B 🔺
CDN Bundle (incl. Tracing, Replay)	79.73 kB	+1.25%	+981 B 🔺
CDN Bundle (incl. Tracing, Replay, Feedback)	85.2 kB	+1.18%	+992 B 🔺
⛔️ CDN Bundle - uncompressed (max: 82 kB)	82.24 kB	+2.75%	+2.2 kB 🔺
⛔️ CDN Bundle (incl. Tracing) - uncompressed (max: 127 kB)	128.42 kB	+2.42%	+3.03 kB 🔺
CDN Bundle (incl. Tracing, Replay) - uncompressed	244.45 kB	+1.26%	+3.03 kB 🔺
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	257.21 kB	+1.2%	+3.03 kB 🔺
⛔️ @sentry/nextjs (client) (max: 47 kB)	47.04 kB	+2.34%	+1.07 kB 🔺
⛔️ @sentry/sveltekit (client) (max: 43 kB)	43.02 kB	+2.63%	+1.1 kB 🔺
@sentry/node-core	51.83 kB	+0.65%	+332 B 🔺
⛔️ @sentry/node (max: 161 kB)	161.92 kB	+1.32%	+2.11 kB 🔺
@sentry/node - without tracing	94.93 kB	+2.17%	+2.01 kB 🔺
@sentry/aws-serverless	110.47 kB	+1.89%	+2.04 kB 🔺

View base workflow run

[github-actions]

node-overhead report 🧳

Note: This is a synthetic benchmark with a minimal express app and does not necessarily reflect the real-world performance impact in an application.

Scenario	Requests/s	% of Baseline	Prev. Requests/s	Change %
GET Baseline	8,706	-	8,957	-3%
GET With Sentry	1,393	16%	1,711	-19%
GET With Sentry (error only)	6,160	71%	6,023	+2%
POST Baseline	1,154	-	1,167	-1%
POST With Sentry	517	45%	559	-8%
POST With Sentry (error only)	1,017	88%	1,035	-2%
MYSQL Baseline	3,309	-	3,296	+0%
MYSQL With Sentry	418	13%	461	-9%
MYSQL With Sentry (error only)	2,684	81%	2,589	+4%

View base workflow run

To fix this problem, the regular expression should be modified to match exactly either "integer" or "double," i.e., the string should be anchored at both the start (^) and end ($). The correct regular expression is /^(integer|double)$/, which matches only the whole string "integer" or "double" and nothing else. This change should be made on line 30 of the file dev-packages/browser-integration-tests/suites/span-first/web-vitals/web-vitals-ttfb/test.ts inside the expect.stringMatching argument. No additional imports or changes are required.

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