Node suggestion: log errors in `unhandledRejection`

[OliverJAsh]

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Package + Version

• @sentry/browser
• @sentry/node
• raven-js
• raven-node (raven for node)
• other:

Version:

4.6.1

Description

Out of the box, Node will log unhandled promise rejections. However, after initialising Sentry, these logs will disappear. This happens because Node won't log rejections if an unhandledRejection handler exists, and Sentry registers such a handler.

I would like to suggest that Sentry adds logging to its handler, to provide parity with the experience provided out of the box. At the very least, the docs should mention this behaviour and the need to add manually an additional handler to restore logging.

[kamilogorek]

Sounds good, however, I'm not sure if this should be behind our debug: true flag.
In the end, you are consciously attaching error handlers, which redirects error stream to the Sentry.

[OliverJAsh]

I'm not sure either.

Enabling Sentry doesn't have the effect of disabling logging for uncaught exceptions, so maybe the same should be true for unhandled promise rejections. (Although this difference in behaviour is more of an inconsistency in Node than Sentry.)

When I enable Sentry I understand it's reporting my errors, but I tend to think of console logging as a separate thing, especially in dev. 🤔

[kamilogorek]

We don't modify default logging behavior, and for uncaught exceptions it's node itself what's triggering a log call.

I think the best solution here would be to just make a note about it in the docs and leave

process.on('unhandledRejection', (reason, p) => {
  console.log('Unhandled Rejection at:', p, 'reason:', reason);
});

snippet in case someone wants to re-enable the warning.

[OliverJAsh]

Docs would suffice. At least then Sentry isn't doing anything special. It's really Node that's the problem here.

[kamilogorek]

Done getsentry/sentry-docs#785

[OliverJAsh]

or uncaught exceptions it's node itself what's triggering a log call.

On second thoughts, I'm not sure that's true.

Sentry registers an uncaughtException handler which disables the default Node behaviour (log + exit).

The handler (defaultOnFatalError) triggers its own log call: https://github.com/getsentry/sentry-javascript/blob/4.6.3/packages/node/src/handlers.ts#L282.

If we're "restoring" logging for uncaught exceptions, I believe we should do the same thing for unhandled promise rejections.

[OliverJAsh]

Can we re-open this? As per my last comment, I now believe Sentry should restore logging for unhandled promise rejections, like it does for uncaught exceptions.

[freeall]

I found this issue because I was starting to use Sentry and wondered if I had made a mistake in my code since only uncaughtException was in my log and not unhandledRejection. It would make a lot of sense for these two cases to be handled the same way.

So I would say either log both or log neither.

[kamilogorek]

I found a better way to handle this, than copying code from Node's core.

λ: node --unhandled-rejections=warn app.js

Also made it obvious by including on the main docs page getsentry/sentry-docs#1099

[OliverJAsh]

I still find it's weird that uncaughtException and unhandledRejection are handled differently. Sentry restores logging for uncaughtException—why doesn't it do the same for unhandledRejection? Users shouldn't have to remember to use that Node flag. 🤔