Sometimes you might have the requirement to override MySQL's default setting for wait_timeout on Acquia Cloud Platform or Acquia Cloud Site Factory.

One possible situation, is your logs may be showing messages like these:

Fatal error: Uncaught PDOException: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away in [..snip..]/core/lib/Drupal/Core/Database/[..snip..]

While implementing an override cannot be done on the MySQL server configuration, directly, as this level of configuration is centrally managed, you can override that setting on a 'per session' basis, i.e. for every PHP process that bootstraps Drupal.

The following provides details for configuring the MySQL wait_timeout value, depending upon your application installation configuration.

$databases['default']['default']['init_commands'] = array(
  'VARIABLE_NAME_1' => 'SET SESSION VARIABLE_NAME_1=VALUE_1',
  'VARIABLE_NAME_2' => 'SET SESSION VARIABLE_NAME_2=VALUE_2',
);

$databases['default']['default']['init_commands'] = [
  'wait_timeout' => 'SET SESSION wait_timeout=<value>'
];

#Example using a value 0f 1200
$databases['default']['default']['init_commands'] = [
  'wait_timeout' => 'SET SESSION wait_timeout=1200'
];

 ¶

Verifying the MySQL transaction settings¶

You can verify the MySQL transaction setting using the following Drush command:

• Run the following Drush command:
  • copy

    drush eval 'print_r(Drupal\Core\Database\Database::getConnection("default", "default")->query("SHOW VARIABLES LIKE '\'wait_timeout\'';")->fetchObject());'

• Expected output:
  • copy

    drush eval 'print_r(Drupal\Core\Database\Database::getConnection("default", "default")->query("SHOW VARIABLES LIKE '\'transaction_isolation\'';")->fetchObject());'
    stdClass Object
    (
        [Variable_name] => wait_timeout
        [Value] => 1200
    )