Default setting for autoInstrumentation.requestHandler as true can truncate MDX output in Astro

[knpwrs]

Is there an existing issue for this?

• I have checked for existing issues https://github.com/getsentry/sentry-javascript/issues
• I have reviewed the documentation https://docs.sentry.io/
• I am using the latest SDK release https://github.com/getsentry/sentry-javascript/releases

How do you use Sentry?

Sentry Saas (sentry.io)

Which SDK are you using?

@sentry/browser

SDK Version

7.91.0

Framework Version

Astro 4.0.7

Link to Sentry event

No response

SDK Setup

export default defineConfig({
  integrations: [
    mdx(),
    sentry({
      debug: true,
      enabled: process.env.NODE_ENV === 'production',
      dsn: '...',
      sourceMapsUploadOptions: {
        project: 'letschurch-astro',
        authToken: process.env.SENTRY_AUTH_TOKEN,
      },
      autoInstrumentation: {
        requestHandler: true,
      },
    }),
  ],
  output: 'server',
  adapter: node({
    mode: 'standalone',
  }),
});

Steps to Reproduce

I am unable to reproduce this issue in isolation and I am seeking further debugging steps.

In my project when I have autoInstrumentation.requestHandler set to true (either as above, or by not specifying autoInstrumentation at all and letting the default value take effect) mdx pages are truncated. Short pages are blank, and long pages have the end cut off.

This does not happen with md or astro pages, only mdx.

Expected Result

The following screenshots are from the end of a long mdx page when autoInstrumentation.requestHandler is set to false:

Actual Result

These screenshots are from the end of that same long mdx page when autoInstrumentation.requestHandler is set to true (or unspecified):

[knpwrs]

This is also in the astro/vite watch dev server, I have not been able to try a built version yet.

[lforst]

I have a suspicion that we are somehow truncating the response stream here:

sentry-javascript/packages/astro/src/server/middleware.ts

Lines 162 to 171 in ea74266

	const newResponseStream = new ReadableStream({
	start: async controller => {
	for await (const chunk of originalBody) {
	const html = typeof chunk === 'string' ? chunk : decoder.decode(chunk);
	const modifiedHtml = addMetaTagToHead(html, scope, client, span);
	controller.enqueue(new TextEncoder().encode(modifiedHtml));
	}
	controller.close();
	},
	});

.

Superficially looking at it I don't see anything immediately wrong. I also have yet to reproduce

I would have one thing I would want to try which would affect non-strictly-utf8-encoded streams: #9989

Maybe you could try an isolated reproduction with non-utf8-encoded files?

I will have @Lms24 take a more educated look next week!

[AbhiPrasad]

We shipped the change mentioned by Luca in https://github.com/getsentry/sentry-javascript/releases/tag/7.92.0 - please give it a try!