Q: Apache Proxy Reroute to Different Port Trying to redirect my subdomain to a different port other than port 80. The request is received via port 80 and I'm trying to direct the requests to port 10001 as there's a mono server running McMyAdmin Panel there and it's a bit annoying telling everyone the port everytime, so I'm trying to make it a bit more convenient, but currently my setup displays this message:
#################### Minecraft Panel Port Redirect Project VHost ####################
<VirtualHost *:80>
   ServerName panel.koangaming.com
   ServerAlias *.panel.koangaming.com

   ProxyPass        / http://localhost:10001/
   ProxyPassReverse / http://localhost:10001/
   ProxyPassReverseCookieDomain localhost panel.koangaming.com
   ProxyPreserveHost On

   ErrorLog "/var/log/koanhosting.in-error_log"
   CustomLog "/var/log/koanhosting.in-access_log" common
</VirtualHost>

Current Error When Loading:
Service Temporarily Unavailable

The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.
Apache/2.2.15 (CentOS) Server at panel.koangaming.com Port 80


[Thu Feb 20 19:25:57 2014] [notice] Digest: generating secret for digest authentication ...
[Thu Feb 20 19:25:57 2014] [notice] Digest: done
[Thu Feb 20 19:25:57 2014] [notice] Apache/2.2.15 (Unix) DAV/2 PHP/5.4.25 configured -- resuming normal operations
[Thu Feb 20 19:26:29 2014] [notice] caught SIGTERM, shutting down
[Thu Feb 20 19:26:30 2014] [notice] SELinux policy enabled; httpd running as context unconfined_u:system_r:httpd_t:s0
[Thu Feb 20 19:26:30 2014] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
[Thu Feb 20 19:26:30 2014] [notice] Digest: generating secret for digest authentication ...
[Thu Feb 20 19:26:30 2014] [notice] Digest: done
    [Thu Feb 20 19:26:30 2014] [notice] Apache/2.2.15 (Unix) DAV/2 PHP/5.4.25 configured -- resuming normal operations
    *** glibc detected *** /usr/sbin/httpd: free(): invalid pointer: 0x00007f1f9f5ced70 ***
    *** glibc detected *** /usr/sbin/httpd: free(): invalid pointer: 0x00007f1f9f5ced70 ***
    [Thu Feb 20 19:26:45 2014] [warn] child process 30673 still did not exit, sending a SIGTERM
    [Thu Feb 20 19:26:45 2014] [warn] child process 30674 still did not exit, sending a SIGTERM
    [Thu Feb 20 19:26:47 2014] [warn] child process 30673 still did not exit, sending a SIGTERM
    [Thu Feb 20 19:26:47 2014] [warn] child process 30674 still did not exit, sending a SIGTERM
    [Thu Feb 20 19:26:49 2014] [warn] child process 30673 still did not exit, sending a SIGTERM
    [Thu Feb 20 19:26:49 2014] [warn] child process 30674 still did not exit, sending a SIGTERM
    [Thu Feb 20 19:26:51 2014] [error] child process 30673 still did not exit, sending a SIGKILL
    [Thu Feb 20 19:26:51 2014] [error] child process 30674 still did not exit, sending a SIGKILL
    [Thu Feb 20 19:26:52 2014] [notice] SELinux policy enabled; httpd running as context unconfined_u:system_r:httpd_t:s0
[Thu Feb 20 19:26:52 2014] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
    [Thu Feb 20 19:26:52 2014] [notice] Digest: generating secret for digest authentication ...
[Thu Feb 20 19:26:52 2014] [notice] Digest: done
[Thu Feb 20 19:26:52 2014] [notice] Apache/2.2.15 (Unix) DAV/2 PHP/5.4.25 configured -- resuming normal operations
sendmail: fatal: chdir /var/spool/postfix: Permission denied
sendmail: fatal: chdir /var/spool/postfix: Permission denied
[Thu Feb 20 20:03:47 2014] [notice] caught SIGTERM, shutting down
[Thu Feb 20 20:03:47 2014] [notice] SELinux policy enabled; httpd running as context unconfined_u:system_r:httpd_t:s0
[Thu Feb 20 20:03:47 2014] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
[Thu Feb 20 20:03:48 2014] [notice] Digest: generating secret for digest authentication ...
[Thu Feb 20 20:03:48 2014] [notice] Digest: done
[Thu Feb 20 20:03:48 2014] [notice] Apache/2.2.15 (Unix) DAV/2 PHP/5.4.25 configured -- resuming normal operations
[Thu Feb 20 20:06:22 2014] [notice] caught SIGTERM, shutting down
[Thu Feb 20 20:06:22 2014] [notice] SELinux policy enabled; httpd running as context unconfined_u:system_r:httpd_t:s0
[Thu Feb 20 20:06:22 2014] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
[Thu Feb 20 20:06:22 2014] [notice] Digest: generating secret for digest authentication ...
[Thu Feb 20 20:06:22 2014] [notice] Digest: done
[Thu Feb 20 20:06:22 2014] [notice] Apache/2.2.15 (Unix) DAV/2 PHP/5.4.25 configured -- resuming normal operations
[Thu Feb 20 20:06:29 2014] [notice] caught SIGTERM, shutting down
[Thu Feb 20 20:06:29 2014] [notice] SELinux policy enabled; httpd running as context unconfined_u:system_r:httpd_t:s0
[Thu Feb 20 20:06:29 2014] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
[Thu Feb 20 19:26:52 2014] [notice] Digest: generating secret for digest authentication ...
[Thu Feb 20 19:26:52 2014] [notice] Digest: done
[Thu Feb 20 19:26:52 2014] [notice] Apache/2.2.15 (Unix) DAV/2 PHP/5.4.25 configured -- resuming normal operations
sendmail: fatal: chdir /var/spool/postfix: Permission denied
sendmail: fatal: chdir /var/spool/postfix: Permission denied
[Thu Feb 20 20:03:47 2014] [notice] caught SIGTERM, shutting down
[Thu Feb 20 20:03:47 2014] [notice] SELinux policy enabled; httpd running as context unconfined_u:system_r:httpd_t:s0
[Thu Feb 20 20:03:47 2014] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
[Thu Feb 20 20:03:48 2014] [notice] Digest: generating secret for digest authentication ...
[Thu Feb 20 20:03:48 2014] [notice] Digest: done
[Thu Feb 20 20:03:48 2014] [notice] Apache/2.2.15 (Unix) DAV/2 PHP/5.4.25 configured -- resuming normal operations
[Thu Feb 20 20:06:22 2014] [notice] caught SIGTERM, shutting down
[Thu Feb 20 20:06:22 2014] [notice] SELinux policy enabled; httpd running as context unconfined_u:system_r:httpd_t:s0
[Thu Feb 20 20:06:22 2014] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
[Thu Feb 20 20:06:22 2014] [notice] Digest: generating secret for digest authentication ...
[Thu Feb 20 20:06:22 2014] [notice] Digest: done
[Thu Feb 20 20:06:22 2014] [notice] Apache/2.2.15 (Unix) DAV/2 PHP/5.4.25 configured -- resuming normal operations
[Thu Feb 20 20:06:29 2014] [notice] caught SIGTERM, shutting down
[Thu Feb 20 20:06:29 2014] [notice] SELinux policy enabled; httpd running as context unconfined_u:system_r:httpd_t:s0
[Thu Feb 20 20:06:29 2014] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
[Thu Feb 20 20:06:29 2014] [notice] Digest: generating secret for digest authentication ...
[Thu Feb 20 20:06:29 2014] [notice] Digest: done
[Thu Feb 20 20:06:29 2014] [notice] Apache/2.2.15 (Unix) DAV/2 PHP/5.4.25 configured -- resuming normal operations
Program mode requires special privileges, e.g., root or TrustedUser.
Program mode requires special privileges, e.g., root or TrustedUser.
Program mode requires special privileges, e.g., root or TrustedUser.
Program mode requires special privileges, e.g., root or TrustedUser.

These are the logs from the 'error_log' file, I can't determine whether they are relevent to the error or not. Possibly somebody who better knows what these mean can decipher.

A: Try to use netcat (nc) or simple telnet client to verify TCP connectivity to that port (from the machine itself):
netcat localhost 10001

Now, you can issue na request to it and see what your app is sending (this one tests GET method):
GET / HTTP/1.1
Host: localhost

Press enter twice and you should get some reply from the listening app similar to this:
HTTP/1.1 200 OK
Date: Thu, 20 Feb 2014 22:00:47 GMT
Server: Apache/2.2.22 (Fedora)
Last-Modified: Tue, 15 Jun 2010 10:41:21 GMT
...
...

If netcatexits immediately or there's no response, then, the listening app seems not to be working properl. 

A: You should look at selinux. In this case you have to set the httpd_can_network_connect sebool variable to allow Apache proxy to connect to the (internal) network.
setsebool -P httpd_can_network_connect 1
See also:
https://serverfault.com/a/911819/188737
https://unix.stackexchange.com/a/8856
