Problems with database connection

Whenever I try to load the sessions library in my controller I get an error message on my page:

Message: mysqli::real_connect(): (HY000/1045): Access denied for user ''@'(my external ip)' (using password: NO)

I think my database.php file is properly configured. x.x.x.x is the ip of a remote database I can connect to through DBeaver. Either way it seems the connection is completely ignoring my configurations.

I should probably add that I'm using docker-compose with this image, but I don't think it's related.

PHP Code:

$db['default'] = array(
    'dsn'    => '',
    'hostname' => 'x.x.x.x',
    'database_user' => 'username',
    'database_password' => 'password',
    'databasename' => 'name',
    'dbdriver' => 'mysqli',
    'dbprefix' => '',
    'pconnect' => FALSE,
    'db_debug' => (ENVIRONMENT !== 'production'),
    'cache_on' => FALSE,
    'cachedir' => '',
    'char_set' => 'utf8',
    'dbcollat' => 'utf8_general_ci',
    'swap_pre' => '',
    'encrypt' => FALSE,
    'compress' => FALSE,
    'stricton' => FALSE,
    'failover' => array(),
    'save_queries' => TRUE
);