Sentry reports handled errors in Fastify integration

[tmcw]

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

8.0.0

Framework Version

4.28.1

Link to Sentry event

No response

Reproduction Example/SDK Setup

No response

Steps to Reproduce

This has already been reported in #12055 but the auto-closer closed it and I can't reopen it, so I'm reporting it again.

Using Sentry.setupFastifyErrorHandler(app) for Fastify leads to Sentry reporting errors for issues that aren't issues: 400s for failed validation, 404s, etc, etc. Lots of errors, lots of noise, all of it not the kind of internal server errors that we want Sentry to track.

A good default might be what the immobiliare 3rd party Sentry plugin has been doing, which is to only track errors with status codes >= 500.

Expected Result

Sentry shouldn't track errors with status < 500 because they are expected.

Actual Result

it tracks all responses with status >= 400

[AbhiPrasad]

Opened #13198 as a PR to address this!

[kblcuk]

Any particular reason using beforeSend hook isn't sufficient in this case?

In JavaScript, you can use a function to modify the event or return a completely new one. You can either return null or an event payload - no other return value (including void) is allowed. If you return null, the event will be discarded.

So in our code we simply do:

Sentry.init({
    dsn,
    beforeSend(event, hint) {
        const error = hint.originalException;
        if (error instanceof ApplicationError && error.statusCode < 500) {
            // drop expected and handled errors,
            // like anything below code 500
            return null;
        }
        return event;
    },
});