I was configuring WordPress with HyperDB plugin on PHP 7.0 but the only I get were constant 500 errors. As I found here PHP 7.0 is not supported by HyperDB for now - it’s rely on mysql php extension but in PHP 7.0 there is only mysqli extension. But few folks fixed it and it’s possible to use it.
curl -O https://raw.githubusercontent.com/soulseekah/hyperdb-mysqli/master/db.php
mv db.php /var/www/wordpress/wp-content/
And configure it ex. like this:
cat <<DBCONFIG > /var/www/wordpress/db-config.php
<?php
\$wpdb->save_queries = false;
\$wpdb->persistent = false;
\$wpdb->max_connections = 10;
\$wpdb->check_tcp_responsiveness = true;
\$wpdb->add_database(array(
'host' => "master.db.host",
'user' => "wordpress",
'password' => "random_password",
'name' => "wordpress",
'write' => 1,
'read' => 1,
));
\$wpdb->add_database(array(
'host' => "slave.db.host",
'user' => "wordpress",
'password' => "random_password",
'name' => "wordpress",
'write' => 0,
'read' => 1,
));
DBCONFIG
Now WordPress could handle crash of master database.