https://wordpress.org/support/topic/too-many-mysql-connections-and-mysql-server-has-gone-away

Check the error logs:

[11-Nov-2014 11:04:24 UTC] WordPress database error MySQL server has gone away for query SELECT ID FROM wp_posts WHERE post_title = 'blog' AND post_type= 'page' made by require('wp-blog-header.php'), require_once('wp-includes/template-loader.php'), include('/themes/cricket_new/page-templates/live_score.php'), include('/themes/cricket_new/includes/right_part.php'), get_page_by_title

Check Mysql

mysql> show status like '%onn%';
+--------------------------+---------+
| Variable_name            | Value   |
+--------------------------+---------+
| Aborted_connects         | 835     |
| Connections              | 3998523 |
| Max_used_connections     | 533     |
| Ssl_client_connects      | 0       |
| Ssl_connect_renegotiates | 0       |
| Ssl_finished_connects    | 0       |
| Threads_connected        | 3       |
+--------------------------+---------+