Enable HAProxy logging on CentOS

By default, HAProxy will not log to files unless we make some modifications
1. Create rsyslog configuration file
nano /etc/rsyslog/haproxy.conf
Add these lines to the file
# Enable UDP port 514 to listen to incoming log messages from haproxy
$ModLoad imudp
$UDPServerRun 514
$template Haproxy,"%msg%\n"
local0.=info -/var/log/haproxy/haproxy.log;Haproxy
local0.notice -/var/log/haproxy/admin.log;Haproxy
# don't log anywhere else
local0.* ~
Restart rsyslog service
/etc/init.d/rsyslog restart
Ref: http://blog.hintcafe.com/post/33689067443/haproxy-logging-with-rsyslog-on-linux
2. Modify the log rotate config to match the new folder:
nano /etc/logrotate.d/haproxy
Change
/var/log/haproxy.log {
    daily
    rotate 10
    missingok
[...]
to
/var/log/haproxy/*.log {
    daily
    rotate 10
    missingok
[...]
Now we can check if HAProxy logging is working.
tail -f /var/log/haproxy/haproxy.log