apache 2.4.6 virtualhost reverse proxy tomcat proxy:error] [pid 3363] AH00940: HTTP: disabled connection for (localhost)

sudo tail -200f /etc/httpd/logs/yourdomainname-error_log

[Mon Nov 12 19:40:54.576505 2018] [proxy:error] [pid 3363] AH00940: HTTP: disabled connection for (localhost)

[Mon Nov 12 19:40:54.615281 2018] [proxy:error] [pid 3365] AH00940: HTTP: disabled connection for (localhost)

Source URL: https://serverfault.com/questions/382076/apache-proxy-not-working-for-a-localhost-port

Here is the solution for your problem:

To turn on this boolean you simple have to use this line (root permissions)

setsebool -P httpd_can_network_connect on

or

sudo setsebool -P httpd_can_network_connect on

Hope that helps. Reference see here: https://wiki.centos.org/TipsAndTricks/SelinuxBooleans