I have seen different threads here, and nothing seems to be work.
Im using LS2 for a while, smoothly and without problems. Few hours ago, suddenly getting this:
Internal Server Error
CDbConnection failed to open the DB connection.
An internal error occurred while the Web server was processing your request. Please contact the webmaster to report this problem.

The MySQL is not dead, cause i can pull information from the LS db tables (from a costume Yii php we have).
Changed also the Db password, still not working.

Any thoughts how it suddenly can happen?

I have have exactly the same issue with the LS site I am running. All was good and the out of the blue with any warning this error message "CDbConnection failed to open the DB connection" appears. The DB login and passwords to the MySql in the config.php have been manually tested and have worked with no issue. Not being a php boff I am now at a bit of a loss and would also request guidance with this.

JdeC wrote: All was good and the out of the blue with any warning this error message "CDbConnection failed to open the DB connection" appears.

Out of the blue should imply that nothing has changed, right?
What OS in which version is used? My guess is a linux distribution.

And LS2 as a version is not enough information to pinpoint the issue. Which version? Which build?

Hi Jelo,

Database & DB-Version: 5.5.42-37.1-log - Percona Server (GPL), Release 37.1, Revision 2
Operating System (Server): linux
Webserver software & version: Apache Version 2.2.31
PHP Version: 5.4.43
LS Version: 151109
URL: 4u2c.co.za/ls/

The hosting company was contacted to understand what upgrades/changes they have implemented in the background and all I was able to get from them was that the systems were running normally. Clearly there was a change somewhere as LS had been running flawlessly.

Is there anyone out there that knows how to resolve this issue?
Looking at the number of people viewing this topic clearly this is an issue that other people are also looking to solve.

I am not an expert, but from the error message I would say that the driver is missing or causing some problems:
Have a look at the PDO driver.

As I can see, you are also not using MySQL, but another server - Percona. It states that it should be compatible, but this can also be a factor that needs to be taken into account. Using this different piece of software makes it also difficult to help from the devolpers side, as they most like don't have Percona running.

Greetings holch, it appears that I cut and pasted the incorrect info with respect to the DB. I am running MySQL 5.5.42 DB after all. I have also been trawling the web for quite some time and still have not resolved the issue. Do you have any further recommendations?

The issue has been resolved due to the a setting in the php.ini file.