One of the most common problems facing a WordPress webmaster is the occasional drop in database connectivity. Left to its own devices, WordPress simply displays to the end user the message
The webmaster has no way of knowing that an error has occurred.
WordPress allows us to address this problem in the following way: if it cannot connect to its database, it will run the drop-in plugin /wp-content/db-error.php (documentation) if it exists. Smart WP db-error.php uses that built-in functionality to serve a 503 page informing users of the outage, while e-mailing webmasters to alert them to the problem -- but only at specified intervals (default: 5 minutes), so as not to overwhelm their mail servers and inboxes.
To install Smart WP db-error.php, execute the following:
cd /path/to/wp-content
git clone https://github.com/agkozak/smart-wp-db-error.git
cd smart-wp-db-error
cp db-error.php.dist ../db-error.php
cd ..At this point it is vitally necessary that you edit the new /wp-content/db-error.php file so as to include installation-specific information. The defaults are
define( 'MAIL_TO', 'Firstname Lastname <example@example.com>' );
define( 'MAIL_FROM', 'example@website.com' );
define( 'ALERT_INTERVAL', 300 ); // In seconds.
define( 'SUPPRESS_CREDITS', false );MAIL_TO and MAIL_FROM should be addresses chosen to cause the least trouble for spam filters (e-mail sent by PHP from a webserver is likely to need whitelisting). ALERT_INTERVAL is the number of seconds between attempts at mailing the webmaster.
If /wp-content/db-error.php is accessed directly, the error page will be displayed, but only for the purposes of showing the webmaster what the error page looks like. No e-mail will be sent. A noindex meta tag reminds search engines never to index the error page (an unlikely event anyway, as the page is served with a 503 status).
If, on the other hand, /wp-content/smart-wp-db-error/smart-wp-db-error.php is accessed directly, the MAIL_TO, MAIL_FROM, and ALERT_INTERVAL constants will not have been defined, and the script will die quietly.