Symfony2：未知的MySQL服务器主机

I struggle connecting my first Symfony App with the online database ( ovh ). Here is the parameters.yml file:

parameters:
    database_host: flibustiyxfolio.mysql.db
    database_port: 3306
    database_name: flibustiyxfolio
    database_user: flibustiyxfolio
    database_password: ***********

I have no clue why it says that it's unknown, is there anything wrong, I need some help.

Ok so I found out, it's again the cache issue in prod env the problem... As I couldn't run the "cache:warmup --env=prod --no-debug" command on the server I had to delete all the cache files and it finally worked.