Catch database exception in Kohana

Question

I'm using Kohana 2. I would like to catch a database exception to prevent an error page when no connection to the server can be established.

The error displayed is

system/libraries/drivers/Database/Mysql.php [61]:

mysql_connect() [function.mysql-connect]: Lost connection to MySQL server at
'reading initial communication packet', system error: 110

The database server is not reachable at all at this point.

I'm doing this from a model. I tried both

public function __construct()
{
    // load database library into $this->db
    try
    {
        parent::__construct();
    }
    catch (Exception $e)
    {
        die('Database error occured');
    }
}

as well as

try
{
    $hoststatus = $this->db->query('SELECT x FROM y WHERE z;');
}
catch (Exception $e)
{
    die('Database error occured');
}

...but none of them seemed to work. It seems as if no exception gets passed on from the main model. Is there another way to catch the database error and use my own error handling?

Answer 1

I don't know Kohana, but a try .. catch block will not catch normal errors, only Exceptions. Are you sure Kohana throws Exceptions where you expect to receive Exceptions?

Edit based on you comments:
Well, first of all, in a production environment (meaning your live application) you should always disable the displaying of PHP errors to the screen. Displaying of these errors to the screen should only be done in a development environment to inform you, the developer. Visitors of your live application however have no business in knowing/reading PHP errors, as it might disclose sensitive information about your environment. You should however log the errors to a log file.

Furthermore, I just took a quick peek at Kohana, and indeed see that here and there Exceptions are thrown, but it doesn't seem to do this in a consistent manner.

If you want php errors to be treated as Exceptions have a look example #1 in this documentation.

Answer 2

You can catch the exception, but you are probably trying to catch it in the wrong place. The problem with trying to catch that low-level of an exception is that it can be spawned from many different sources.

For example, if you use the database driver for your sessions that exception will be thrown from instantiation of the database driver in the session library (which is instantiated in a call to session which will probably happen before you instantiate any models).

Catching that exception can happen from the model, but it is more likely to happen from another source - in which case you would probably have to extend a few libraries, or be sure you are wrapping a base model parent::__construct call and the session library in a try-catch block.

(I would personally extend the Model library to do that instead of putting it in a base model)

Hope that helps.

Answer 3

Kohana 2 does not convert errors into exceptions. You will either need to attach your own error handler, or use error_reporting() to turn off the error (temporarily) then do some kind of handling yourself.