Symfony services.yaml handle exception - symfony

Question

In my services.yaml, I'm having this code:
services:
# prepare database
DatabaseProvider:
class: Kepler\Providers\DatabaseProvider
arguments: ['%database.reader.dsn%', '%database.reader.username%', '%database.reader.password%']
ReaderPDO:
class: PDO
factory: ['#DatabaseProvider', generateDatabaseConnection]
WriterPDO:
class: PDO
factory: ['#DatabaseProvider', generateDatabaseConnection]
And DatabaseProvider:generateDatabaseConnection
public function generateDatabaseConnection() {
try {
return new PDO($this->host, $this->username, $this->password);
} catch (Exception $e) {
return new PDO($this->host, $this->username, $this->password);
$_GLOBALS['db_error'] = true;
}
}
So my question is here: There will be cases where the PDO connection is not working/failing. So how I catch this exception and return the general 404 page (This is the page where I don't need any db connection)?
Some basic analysis:
I believe this is failing during symfony booting up
Even if I return null, or return nothing in the catch, the code will keep continue autowiring, which will then fail in Controller that requires DB connection

Answer 1

having a return in a catch block should be considered harmful if it's exactly the same thing to be returned as in the try block.
Setting a global value is really old-school and not really the symfony way. Instead, you would throw a specific exception (or just not catch the PDO one), and add an event listener for the kernel exception that will result from that, where you may look for that specific exception and return the proper error page you want.
If you just want the 404 page, you can throw the NotFoundHttpException or maybe more appropriate the ServiceUnavailableException ...