Yii2怎么配置主从服务器？

'ggddb' => [

    'class' => 'yii\db\Connection',

    'dsn' => 'mysql:host='.$_SERVER['ACTIVITY_W_DB_HOST'].';dbname='.$_SERVER['ACTIVITY_W_DB_NAME'].';port='.$_SERVER['ACTIVITY_W_DB_PORT'],

    'username' => $_SERVER['ACTIVITY_W_DB_USER'],

    'password' => $_SERVER['ACTIVITY_W_DB_PWD'],

    'charset' => 'utf8',

]

'ggddb2' => [

	'class' => 'yii\db\Connection',

	'charset' => 'utf8',

	'masterConfig' => [

		'username' => $_SERVER['ACTIVITY_W_DB_USER'],

		'password' => $_SERVER['ACTIVITY_W_DB_PWD'],

		'attributes' => [

			PDO::ATTR_TIMEOUT => 10

		]

	],

	'masters' => [

 		['dsn'] => 'mysql:host='.$_SERVER['ACTIVITY_W_DB_HOST'].';dbname='.$_SERVER['ACTIVITY_W_DB_NAME'].';port='.$_SERVER['ACTIVITY_W_DB_PORT']

	],



	'slaveConfig' => [

		'username' => $_SERVER['ACTIVITY_R_DB_USER'],

		'password' => $_SERVER['ACTIVITY_R_DB_PWD'],

		'attributes' => [

			PDO::ATTR_TIMEOUT => 10

		]

	],

	'slaves' => [

		['dsn'] => 'mysql:host='.$_SERVER['ACTIVITY_R_DB_HOST'].';dbname='.$_SERVER['ACTIVITY_R_DB_NAME'].';port='.$_SERVER['ACTIVITY_R_DB_PORT']

	]



]