(13)Permission denied: proxy: HTTP: attempt to connect to 127.0.0.1:8080 (localhost) failed – this error is because of httpd/apache2 has been denied permission to connect to IP address and port.
Main reason for this error is SELinux. Here SELinux not permitting httpd/apache2 to make network connections.
To resolve it, you need to change an SELinux boolean value (which will automatically persist across reboots). You may also required to restart httpd/apache2 to reset the proxy worker, although this isn’t strictly required.
Run either of following command to allow SELinux to permit httpd/apache2 to make network connections:
$ /usr/sbin/setsebool httpd_can_network_connect 1
$ /usr/sbin/setsebool httpd_can_network_connect true
Then restart httpd/apache2.