fix: set headers before they get frozen

Author: logaretm

packages/nitro/src/runtime/hooks/captureTracingEvents.ts

@@ -19,6 +19,7 @@ import {
 import type { TracingRequestEvent as H3TracingRequestEvent } from 'h3/tracing';
 import { tracingChannel } from 'otel-tracing-channel';
 import type { RequestEvent as SrvxRequestEvent } from 'srvx/tracing';
+import { setServerTimingHeaders } from './setServerTimingHeaders';
 
 /**
  * Global object with the trace channels
@@ -118,7 +119,9 @@ function setupH3TracingChannels(): void {
   });
 
   h3Channel.subscribe({
-    start: NOOP,
+    start: (data: H3TracingRequestEvent) => {
+      setServerTimingHeaders(data.event);
+    },
     asyncStart: NOOP,
     end: NOOP,
     asyncEnd: (data: H3TracingRequestEvent & { span?: Span; result?: unknown }) => {

packages/nitro/src/runtime/hooks/setServerTimingHeaders.ts

@@ -1,19 +1,27 @@
 import { getTraceData } from '@sentry/core';
+import type { TracingRequestEvent as H3TracingRequestEvent } from 'h3/tracing';
 
 /**
  * Sets Server-Timing response headers for trace propagation to the client.
  * The browser SDK reads these via the Performance API to connect pageload traces.
  */
-export function setServerTimingHeaders(response: unknown, _event: unknown): void {
-  if (response && typeof response === 'object' && 'headers' in response) {
-    const responseObj = response as Response;
-    const traceData = getTraceData();
+export function setServerTimingHeaders(event: H3TracingRequestEvent['event']): void {
+  if (event.context._sentryServerTimingSet) {
+    return;
+  }
+
+  const headers = event.res?.headers;
+  if (!headers) {
+    return;
+  }
 
-    if (traceData['sentry-trace']) {
-      responseObj.headers.append('Server-Timing', `sentry-trace;desc="${traceData['sentry-trace']}"`);
-    }
-    if (traceData.baggage) {
-      responseObj.headers.append('Server-Timing', `baggage;desc="${traceData.baggage}"`);
-    }
+  const traceData = getTraceData();
+  if (traceData['sentry-trace']) {
+    headers.append('Server-Timing', `sentry-trace;desc="${traceData['sentry-trace']}"`);
   }
+  if (traceData.baggage) {
+    headers.append('Server-Timing', `baggage;desc="${traceData.baggage}"`);
+  }
+
+  event.context._sentryServerTimingSet = true;
 }

packages/nitro/src/runtime/plugins/server.ts

@@ -1,16 +1,11 @@
 import { definePlugin } from 'nitro';
 import { captureErrorHook } from '../hooks/captureErrorHook';
 import { captureTracingEvents } from '../hooks/captureTracingEvents';
-import { setServerTimingHeaders } from '../hooks/setServerTimingHeaders';
 
 export default definePlugin(nitroApp => {
   // FIXME: Nitro hooks are not typed it seems
   // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access
   nitroApp.hooks.hook('error', captureErrorHook);
 
-  // FIXME: Nitro hooks are not typed it seems
-  // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access
-  nitroApp.hooks.hook('response', setServerTimingHeaders);
-
   captureTracingEvents();
 });