r3vers3 on "[Plugin: HyperDB] Failover configuration"

Hello,
I have one nginx server with wordpress 4.4.1 installed. I have two MySQL VM's (replication configured - IP x.20 is master / x.21 is slave).

HyperDB configuration looks like below:

$wpdb->add_database(array(
	'host'     => '192.168.100.20',     // If port is other than 3306, use host:port.
	'user'     => 'root',
	'password' => 'pass',
	'name'     => 'wordpress',
	'write' => 1,
	'read' => 1,
	'timeout'  => 0.2,
));

$wpdb->add_database(array(
	'host'     => '192.168.100.21',     // If port is other than 3306, use host:port.
	'user'     => 'root',
	'password' => 'pass',
	'name'     => 'wordpress',
	'write'    => 0,
	'read'     => 1,
	'timeout'  => 0.2,
));

But when I turn off 1st (master) MySQL server I got error, that MySQL server is unavaliable - it's still trying to connect to the master server on 192.168.100.20 IP address.

All files are in proper location.

https://wordpress.org/plugins/hyperdb/