Application Instantiation Error: Could not connect to MySQL.

[NickY]

Hi, it is almost daily now that my server drops with the message:
Error displaying the error page: Application Instantiation Error: Could not connect to MySQL.
I have looked into my httpd error logs and found the following:

[Sat Dec 10 22:58:06 2016] [notice] FastCGI: process manager initialized (pid 19164)
[Sat Dec 10 22:58:06 2016] [notice] Apache/2.2.31 (Unix) DAV/2 mod_fastcgi/2.4.7 mod_rpaf/0.6 mod_ssl/2.2.31 OpenSSL/1.0.1e-fips mod_perl/2.0.4 Perl/v5.10.1 configured -- resuming normal operations
[Sun Dec 11 00:58:52 2016] [error] [client 185.159.37.21] File does not exist: /home/kloxo/httpd/default/.git
[Sun Dec 11 02:06:08 2016] [error] [client 180.76.15.8] File does not exist: /home/kloxo/httpd/default/result
[Sun Dec 11 02:41:22 2016] [error] [client 193.201.224.223] File does not exist: /home/kloxo/httpd/default/administrator, referer: http://ns1.mychatbuddy.com/administrator/index.php
[Sun Dec 11 02:41:40 2016] [error] [client 193.201.224.223] File does not exist: /home/kloxo/httpd/default/administrator, referer: http://ns2.mychatbuddy.com/administrator/index.php
[Sun Dec 11 02:41:42 2016] [error] [client 193.201.224.223] File does not exist: /home/kloxo/httpd/default/administrator, referer: http://ns2.mychatbuddy.com/administrator/index.php
[Sun Dec 11 02:41:50 2016] [error] [client 193.201.224.223] File does not exist: /home/kloxo/httpd/default/administrator, referer: http://ns2.mychatbuddy.com/administrator/index.php
[Sun Dec 11 03:23:59 2016] [error] [client 222.186.58.12] File does not exist: /home/kloxo/httpd/default/phpmyadmin, referer: http://104.168.137.189/phpmyadmin
[Sun Dec 11 03:24:18 2016] [error] [client 185.159.37.21] File does not exist: /home/kloxo/httpd/default/.git
[Sun Dec 11 03:49:15 2016] [error] [client 180.76.15.6] File does not exist: /home/kloxo/httpd/default/privacy
[Sun Dec 11 05:38:58 2016] [error] [client 89.248.169.50] File does not exist: /home/kloxo/httpd/default/muieblackcat
[Sun Dec 11 05:38:59 2016] [error] [client 89.248.169.50] File does not exist: /home/kloxo/httpd/default/mysql
[Sun Dec 11 05:59:03 2016] [error] [client 141.212.122.16] client sent HTTP/1.1 request without hostname (see RFC2616 section 14.23): /x
[Sun Dec 11 06:09:58 2016] [notice] caught SIGTERM, shutting down
[Sun Dec 11 06:09:58 2016] [alert] (4)Interrupted system call: FastCGI: read() from pipe failed (0)
[Sun Dec 11 06:09:58 2016] [alert] (4)Interrupted system call: FastCGI: the PM is shutting down, Apache seems to have disappeared - bye

What exactly is the problem in your opinion? Fast CGI or SSL certifcate config?
Many thanks.
Nick

[MRatWork]

Someone try to access/explore your server.

[NickY]

Thank you. That's what I suspected. How can I blacklist the addresses?
Many thanks.
Nick

[MRatWork]

Add their IP to 'Blocked Hosts'.