Delay exit in error handler

[arrilot]

Q	A
Is bugfix?	✔️
New feature?	❌
Breaks BC?	❌ i suppose it's not likely that anyone relies on the current behavior

Our use case is the following. We want to collect prometheus metrics regarding http requests and console commands - rps, duration, number of errors, timeouts e.t.c.
The way we do it is via register_shutdown_function in a filter attached to route or application.
The problem is that ErrorHandler gets on the road.
Error handler registers its own register_shutdown_function callback and when a fatal error occurs (e.g. a request exceeds max_execution_time) calls exit(1) in the end of it. As a result no other register_shutdown_function` callbacks registered in userland have a chance to be invoked and we lose all the metrics for this request.
It is also worth noting that errorHandler is registered in Yii Application very early during request lifecycle that makes things even worse.

This is by no mean a new issue. It was raised at least one, two times

In the last issue Cebe said "If you have any alternative fixes in mind, feel free to do a suggestion" so here we go.

The idea was taken from Yii's logger - https://github.com/yiisoft/yii2/blob/master/framework/log/Logger.php#L135
According to php docs "Shutdown functions may also call register_shutdown_function() themselves to add a shutdown function to the end of the queue."
By moving exit(1) to the end shutdown callbacks queue we preserve the final exit code and leave a room for developers' own callbacks to be executed.

[bizley]

Interesting. And it was @dynasource, not @cebe btw ;)
It would be nice to have a test registering additional shutdown.

[arrilot]

Frankly, I have no idea how something like that can be tested because:

1. register_shutdown_function callbacks are never executed during phpunit tests
2. php does not even expose a list of registered shutdown functions

[WinterSilence]

Note: it's only questions.

Yii Application very early during request lifecycle that makes things even worse.

as any other frameworks/applications. why not use YII_ENABLE_ERROR_HANDLER and any handler or Yii container($config['components']['errorHandler']['class']) and custom yii\base\ErrorHandler?

[WinterSilence]

@arrilot what's you think about PR #19402 ? we can run custom shutdown handler before exit()

[samdark]

Logically it looks alright.

[arrilot]

@arrilot what's you think about PR #19402 ? we can run custom shutdown handler before exit()

It's okay.

+ more flexible
+ bc-friendly
- less intuitive for developers. They need to face the issue, do the research, and write a couple of lines to implement solution
- does not help if register_shutdown_function is registred as a part of 3rd party code inside vendor

I'm fine with any of these approaches. It's up to core team to decide which they like more

[bizley]

Hm, and how about combining the two?

[arrilot]

Yeah, it's possible aswell

[WinterSilence]

• less intuitive for developers.

api/guide display @events. I don't think many users will need something like this. On my prev work too using Prometheus, but by beforeSend event.

• does not help if register_shutdown_function is registred as a part of 3rd party code inside vendor

what you mean?

[samdark]

@arrilot would you please add a line for CHANGELOG? Thanks.

[arrilot]

@samdark Done

[samdark]

Thanks!