fix(nextjs): Avoid sending http.client transactions for Sentry fetch requests on edge & dev env

[mydea]

This should fix #16502, but we do not have a fix yet.
But tests show the problem....

[github-actions]

size-limit report 📦

Path	Size	% Change	Change
@sentry/browser	23.99 kB	-	-
@sentry/browser - with treeshaking flags	23.76 kB	-	-
@sentry/browser (incl. Tracing)	39.02 kB	-	-
@sentry/browser (incl. Tracing, Replay)	77.16 kB	-	-
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	70.25 kB	-	-
@sentry/browser (incl. Tracing, Replay with Canvas)	81.93 kB	-	-
@sentry/browser (incl. Tracing, Replay, Feedback)	94.02 kB	-	-
@sentry/browser (incl. Feedback)	40.75 kB	-	-
@sentry/browser (incl. sendFeedback)	28.7 kB	-	-
@sentry/browser (incl. FeedbackAsync)	33.59 kB	-	-
@sentry/react	25.76 kB	-	-
@sentry/react (incl. Tracing)	41 kB	-	-
@sentry/vue	28.36 kB	-	-
@sentry/vue (incl. Tracing)	40.86 kB	-	-
@sentry/svelte	24.01 kB	-	-
CDN Bundle	25.5 kB	-	-
CDN Bundle (incl. Tracing)	39.11 kB	-	-
CDN Bundle (incl. Tracing, Replay)	75 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback)	80.46 kB	-	-
CDN Bundle - uncompressed	74.5 kB	-	-
CDN Bundle (incl. Tracing) - uncompressed	116.63 kB	-	-
CDN Bundle (incl. Tracing, Replay) - uncompressed	230.68 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	243.5 kB	-	-
@sentry/nextjs (client)	42.63 kB	-	-
@sentry/sveltekit (client)	39.49 kB	-	-
@sentry/node	154.29 kB	-0.01%	-1 B 🔽
@sentry/node - without tracing	98.64 kB	-	-
@sentry/aws-serverless	124.4 kB	-	-

View base workflow run

[cursor]

Bug: Event Processor Registration Fails on Early SDK Initialization

The change from getGlobalScope().addEventProcessor() to client?.addEventProcessor() prevents critical event processors from being registered when the client is undefined. This occurs when the SDK's init() function returns early, such as when isBuild() or sdkAlreadyInitialized() is true. Consequently, essential functionality like transaction filtering (e.g., for static assets, Sentry requests, 404s) and error handling (e.g., React control flow errors like postpone/suspense) is bypassed, leading to unwanted data being sent to Sentry or important errors not being filtered.

packages/nextjs/src/server/index.ts#L206-L378

sentry-javascript/packages/nextjs/src/server/index.ts

Lines 206 to 378 in 188a8ff

	client?.addEventProcessor(
	Object.assign(
	(event => {
	if (event.type === 'transaction') {
	// Filter out transactions for static assets
	// This regex matches the default path to the static assets (`_next/static`) and could potentially filter out too many transactions.
	// We match `/_next/static/` anywhere in the transaction name because its location may change with the basePath setting.
	if (event.transaction?.match(/^GET (\/.*)?\/_next\/static\//)) {
	return null;
	}
	// Filter out transactions for requests to the tunnel route
	if (
	(globalWithInjectedValues._sentryRewritesTunnelPath &&
	event.transaction === `POST ${globalWithInjectedValues._sentryRewritesTunnelPath}`) ||
	(process.env._sentryRewritesTunnelPath &&
	event.transaction === `POST ${process.env._sentryRewritesTunnelPath}`)
	) {
	return null;
	}
	// Filter out requests to resolve source maps for stack frames in dev mode
	if (event.transaction?.match(/\/__nextjs_original-stack-frame/)) {
	return null;
	}
	// Filter out /404 transactions which seem to be created excessively
	if (
	// Pages router
	event.transaction === '/404' ||
	// App router (could be "GET /404", "POST /404", ...)
	event.transaction?.match(/^(GET|HEAD|POST|PUT|DELETE|CONNECT|OPTIONS|TRACE|PATCH) \/(404|_not-found)$/)
	) {
	return null;
	}
	// Filter transactions that we explicitly want to drop.
	if (event.contexts?.trace?.data?.[TRANSACTION_ATTR_SHOULD_DROP_TRANSACTION]) {
	return null;
	}
	// Next.js 13 sometimes names the root transactions like this containing useless tracing.
	if (event.transaction === 'NextServer.getRequestHandler') {
	return null;
	}
	// Next.js 13 is not correctly picking up tracing data for trace propagation so we use a back-fill strategy
	if (typeof event.contexts?.trace?.data?.[TRANSACTION_ATTR_SENTRY_TRACE_BACKFILL] === 'string') {
	const traceparentData = extractTraceparentData(
	event.contexts.trace.data[TRANSACTION_ATTR_SENTRY_TRACE_BACKFILL],
	);
	if (traceparentData?.parentSampled === false) {
	return null;
	}
	}
	// On Edge Runtime, fetch requests can leak to the Node runtime fetch instrumentation
	// and end up being sent as transactions to Sentry.
	// We filter them here based on URL
	if (event.contexts?.trace?.data?.[SEMANTIC_ATTRIBUTE_SENTRY_OP] === 'http.client') {
	const url = event.contexts?.trace?.data?.['url'];
	if (url && isSentryRequestUrl(url, client)) {
	return null;
	}
	}
	return event;
	} else {
	return event;
	}
	}) satisfies EventProcessor,
	{ id: 'NextLowQualityTransactionsFilter' },
	),
	);
	client?.addEventProcessor(
	Object.assign(
	((event, hint) => {
	if (event.type !== undefined) {
	return event;
	}
	const originalException = hint.originalException;
	const isPostponeError =
	typeof originalException === 'object' &&
	originalException !== null &&
	'$$typeof' in originalException &&
	originalException.$$typeof === Symbol.for('react.postpone');
	if (isPostponeError) {
	// Postpone errors are used for partial-pre-rendering (PPR)
	return null;
	}
	// We don't want to capture suspense errors as they are simply used by React/Next.js for control flow
	const exceptionMessage = event.exception?.values?.[0]?.value;
	if (
	exceptionMessage?.includes('Suspense Exception: This is not a real error!') ||
	exceptionMessage?.includes('Suspense Exception: This is not a real error, and should not leak')
	) {
	return null;
	}
	return event;
	}) satisfies EventProcessor,
	{ id: 'DropReactControlFlowErrors' },
	),
	);
	// Use the preprocessEvent hook instead of an event processor, so that the users event processors receive the most
	// up-to-date value, but also so that the logic that detects changes to the transaction names to set the source to
	// "custom", doesn't trigger.
	client?.on('preprocessEvent', event => {
	// Enhance route handler transactions
	if (
	event.type === 'transaction' &&
	event.contexts?.trace?.data?.['next.span_type'] === 'BaseServer.handleRequest'
	) {
	event.contexts.trace.data[SEMANTIC_ATTRIBUTE_SENTRY_OP] = 'http.server';
	event.contexts.trace.op = 'http.server';
	if (event.transaction) {
	event.transaction = stripUrlQueryAndFragment(event.transaction);
	}
	// eslint-disable-next-line deprecation/deprecation
	const method = event.contexts.trace.data[SEMATTRS_HTTP_METHOD];
	// eslint-disable-next-line deprecation/deprecation
	const target = event.contexts?.trace?.data?.[SEMATTRS_HTTP_TARGET];
	const route = event.contexts.trace.data[ATTR_HTTP_ROUTE] || event.contexts.trace.data['next.route'];
	if (typeof method === 'string' && typeof route === 'string') {
	const cleanRoute = route.replace(/\/route$/, '');
	event.transaction = `${method} ${cleanRoute}`;
	event.contexts.trace.data[SEMANTIC_ATTRIBUTE_SENTRY_SOURCE] = 'route';
	// Preserve next.route in case it did not get hoisted
	event.contexts.trace.data['next.route'] = cleanRoute;
	}
	// backfill transaction name for pages that would otherwise contain unparameterized routes
	if (event.contexts.trace.data[TRANSACTION_ATTR_SENTRY_ROUTE_BACKFILL] && event.transaction !== 'GET /_app') {
	event.transaction = `${method} ${event.contexts.trace.data[TRANSACTION_ATTR_SENTRY_ROUTE_BACKFILL]}`;
	}
	// Next.js overrides transaction names for page loads that throw an error
	// but we want to keep the original target name
	if (event.transaction === 'GET /_error' && target) {
	event.transaction = `${method ? `${method} ` : ''}${target}`;
	}
	}
	// Next.js 13 is not correctly picking up tracing data for trace propagation so we use a back-fill strategy
	if (
	event.type === 'transaction' &&
	typeof event.contexts?.trace?.data?.[TRANSACTION_ATTR_SENTRY_TRACE_BACKFILL] === 'string'
	) {
	const traceparentData = extractTraceparentData(event.contexts.trace.data[TRANSACTION_ATTR_SENTRY_TRACE_BACKFILL]);
	if (traceparentData?.traceId) {
	event.contexts.trace.trace_id = traceparentData.traceId;
	}
	if (traceparentData?.parentSpanId) {
	event.contexts.trace.parent_span_id = traceparentData.parentSpanId;
	}
	}
	});
	if (process.env.NODE_ENV === 'development') {
	client?.addEventProcessor(devErrorSymbolicationEventProcessor);

Fix in Cursor

---

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[bricefriha]

A bit unrelated to this PR, is there a reason why we are returning the event in an else block?
Wouldn't it make more sense to remove the else and return the event after the if statement?

[mydea]

Update: This is not reliable enough, other fetch requests still leak to the node SDK, so closing this in favor of just warning about this.