Why is Sentry logging an error even though the exception has been caught by Symfony?

[ericmorand]

We are currently investigating why our sentry logs are spammed with non-relevant errors like 4xx HTTP ones, and we discovered that the Sentry Symfony package actually log some errors even though the framework catches the exceptions - and translate them into proper HTTP responses.

Does it mean that sentry logs the errors before the framework has a chance to catch them? If so, how can we prevent that?

It does not make sense to add some ignored exceptions (through ignore_exceptions) since 4xx response are not exceptions to begin with. Symfony internally uses such a mechanism (which is already very debatable), but they are not exceptions: they are client-side errors, nothing went wrong on the server, there is no reason why sentry would log anything here.

Can someone help us understand the unexpected behavior of Symfony Sentry?

[Litarnus]

Hi! While they might not act semantically like regular exceptions, they are still exceptions and will produce an ExceptionEvent, which Sentry will capture using the ErrorListener

Instead of having a list of ignore_exceptions, you can also inspect the events in the before_send callback and drop those events there.

[ericmorand]

Thanks a lot for the clarification. Much appreciated.

[ericmorand]

@Litarnus, I'm not sure I understand how before_send can be used in this context. It seems like Sentry is swallowing the exception that was raised, and it can't be retrieved from the $event argument. If I'm not mistaken, it means that there is no way to detect HTTP exceptions status code since the exception is not retrievable at all.

I may need to open another topic though.

[Litarnus]

@ericmorand before_send receives an EventHint as second parameter which then contains the exception and you can perform an instanceof check

[ericmorand]

Interesting. I'm unable to find the documentation for the send_before signature, but you are correct, it does receives a second argument. Where did you find the documentation for this?

Also, we ended up using our own HubInterface implementation, and overriding captureEvent, which at least is documented and typed.

[Litarnus]

You can find it here: https://docs.sentry.io/platforms/php/guides/symfony/configuration/options/#before_send

Generally for options related things, you can look at https://docs.sentry.io/platforms/php/guides/symfony/configuration/options/ or https://docs.sentry.io/platforms/php/guides/symfony/configuration/symfony-options/