HAProxy : HTTP Load Balancing2021/03/17

Install HAProxy to configure Load Balancing Server.
This example is based on the environment like follows.

-----------+---------------------------+--------------------------+------------
           |                           |                          |
           |10.0.0.30                  |10.0.0.51                 |10.0.0.52
+----------+-----------+   +-----------+----------+   +-----------+----------+
|   [ dlp.srv.world ]  |   | [ node01.srv.world ] |   | [ node02.srv.world ] |
|        HAProxy       |   |      Web Server#1    |   |      Web Server#2    |
+----------------------+   +----------------------+   +----------------------+

	Configure Servers that HTTP connection to HAProxy Server is forwarded to backend Web Servers.
[1]	Install HAProxy.

[root@dlp ~]#

dnf -y install haproxy

[2]	Configure HAProxy.

[root@dlp ~]#

vi /etc/haproxy/haproxy.cfg

# comment out all for existing [frontend ***] [backend ***] sections
# and add follows to the end
# define frontend ( any name is OK for [http-in] )
frontend http-in
    # listen 80 port
    bind *:80
    # set default backend
    default_backend    backend_servers
    # send X-Forwarded-For header
    option             forwardfor

# define backend
backend backend_servers
    # balance with roundrobin
    balance            roundrobin
    # define backend servers
    server             node01 10.0.0.51:80 check
    server             node02 10.0.0.52:80 check

[root@dlp ~]#

systemctl enable --now haproxy

[3]	If Firewalld is running, allow ports HAProxy listens.

[root@dlp ~]#

firewall-cmd --add-service=http --permanent

success
[root@dlp ~]#

firewall-cmd --reload

success

[4]	By default setting of HAproxy, logs are sent to [local2] facility, so Configure Rsyslog to record it to a file.

[root@dlp ~]#

vi /etc/rsyslog.conf

# line 19,20 : uncomment and add a line

module(load="imudp") # needs to be done just once
input(type="imudp" port="514")

$AllowedSender UDP, 127.0.0.1

# line 46 : change like follows

*.info;mail.none;authpriv.none;cron.none;local2.none    /var/log/messages
local2.*                                                /var/log/haproxy.log

[root@dlp ~]#

systemctl restart rsyslog

[5]	Change settings on Backends Web server (Apache httpd on this example) to logging X-Forwarded-For header.

[root@node01 ~]#

vi /etc/httpd/conf/httpd.conf

# line 199 : change like follows

LogFormat "

\"%{X-Forwarded-For}i\"

%l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined

[root@node01 ~]#

systemctl restart httpd

[6]	Verify working normally to access to frontend HAproxy Server.

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