===== HA Proxy =====
==== Install ====
<code>
yum install haproxy
</code>

==== Configure ====

Edit /etc/haproxy/haproxy.cfg

<code>
frontend apache
        mode tcp
        bind 172.19.65.206:80
        default_backend apache-servers

backend apache-servers
        balance roundrobin
        mode tcp
        server apache1 172.19.65.207:80
</code>

Execute:
<code>
systemctl enable haproxy
systemctl start haproxy

firewall-cmd --permanent --add-service=http
firewall-cmd --permanent --add-service=https
firewall-cmd --reload
</code>

==== Configure rsyslog ====
Edit /etc/rsyslog.conf
<code>
# Provides UDP syslog reception
$UDPServerAddress 127.0.0.1
$ModLoad imudp
$UDPServerRun 514

# Save logs for haproxy global configs
local2.*                       /var/log/haproxy.log

# Save logs for haproxy lapoc frontend
local0.*                       /var/log/haproxy-apache.log
</code>

Execute:
<code>
systemctl restart rsyslog
</code>

==== Subdomain configuration ====

Edit /etc/haproxy/haproxy.cfg
<code>
frontend lapoc
        log 127.0.0.1 local0 debug
        option httplog
        option forwardfor
        mode http
        bind 172.19.65.206:80
        acl apache_sub hdr(host) -i apache.gbmdc.dc
        acl tomcat_sub hdr(host) -i tomcat.gbmdc.dc
	use_backend apache-servers if apache_sub
        use_backend tomcat-servers if tomcat_sub

	
backend apache-servers
        mode http
        option httplog
        option forwardfor
        server apache1 172.19.65.207:80

backend tomcat-servers
        mode http
        option httplog
        option forwardfor
        server tomcat1 172.19.65.207:8080
</code>

==== Enable stats ====
Edit /etc/haproxy/haproxy.cfg
<code>
listen stats
    bind *:9000
    stats enable
    stats uri /
    stats refresh 5s
    stats auth cmorun:Manager20.
</code>

Execute:
<code>
firewall-cmd --permanent --add-port=9000/tcp
</code>


==== Upgrade to HA Proxy 1.8 ====
<code>
yum-config-manager --enable rhel-server-rhscl-7-rpms
yum install rh-haproxy18
</code>

You can use this commando to enable in the session:
<code>
scl enable rh-haproxy18 bash
</code>

You need to change the file /etc/opt/rh/rh-haproxy18/haproxy/haproxy.cfg to reflect changes.

Execute:
<code>
systemctl disable haproxy
systemctl stop haproxy
systemctl enable rh-haproxy18-haproxy
systemctl start rh-haproxy18-haproxy
</code>

==== References ====
  * https://www.serverlab.ca/tutorials/linux/network-services/layer-4-load-balancing-with-haproxy/
  * https://www.haproxy.com/blog/introduction-to-haproxy-logging/
  * https://blog.entrostat.com/routing-multiple-domains-using-haproxy-http-and-https-ssl/
  * https://freedif.org/redirect-a-subdomain-to-a-vm-with-haproxy