Install HAProxy on CentOS 8 - Step by step guide ?

HAProxy is a free HTTP/TCP high availability load balancer and proxy server. It spreads requests among multiple servers to mitigate issues resulting from a single server failure. HA Proxy is used by a number of high-profile websites including GitHub, Bitbucket, Stack Overflow, Reddit, Tumblr, Twitter, and Tuenti, and is used in the OpsWorks product from Amazon Web Services.

Here at LinuxAPT, as part of our Server Management Services, we regularly help our Customers to perform related HAProxy configuration queries.

In this context, we shall look into how to install HAProxy on your CentOS 8 system.

Steps to Install and configure HAProxy on CentOS 8

1. Perform System Update

First, let's start by ensuring your system is up-to-date:

$ sudo clean all
$ sudo dnf update

2. Install HAProxy on the system

HAProxy is available on the default CentOS 8, Now use the following dnfa command to install HAProxy:

$ sudo dnf install haproxy

Next, we have to verify that HAProxy starts every time we reboot our server. We can accomplish that with the chkconfig command below:

$ chkconfig haproxy on

3. Configure HAProxy

We are going to create a configuration file /etc/haproxy/haproxy.cfg containing the necessary settings and configurations:

$ sudo nano /etc/haproxy/haproxy.cfg

Enter the following into the file:

global
    log         127.0.0.1 local2
    chroot      /var/lib/haproxy
    pidfile     /var/run/haproxy.pid
    maxconn     4000
    user        haproxy
    group       haproxy
    daemon
    stats socket /var/lib/haproxy/stats
    ssl-default-bind-ciphers PROFILE=SYSTEM
    ssl-default-server-ciphers PROFILE=SYSTEM
defaults
    mode                    http
    log                     global
    option                  httplog
    option                  dontlognull
    option http-server-close
    option forwardfor       except 127.0.0.0/8
    option                  redispatch
    retries                 3
    timeout http-request    10s
    timeout queue           1m
    timeout connect         10s
    timeout client          1m
    timeout server          1m
    timeout http-keep-alive 10s
    timeout check           10s
    maxconn                 3000
frontend main
    bind *:5000
    acl url_static       path_beg       -i /static /images /javascript /stylesheets
    acl url_static       path_end       -i .jpg .gif .png .css .js
    use_backend static          if url_static
    default_backend             app
backend static
    balance     roundrobin
    server      static 127.0.0.1:4331 check
backend app
    balance     roundrobin
    server  app1 127.0.0.1:5001 check
    server  app2 127.0.0.1:5002 check
    server  app3 127.0.0.1:5003 check
    server  app4 127.0.0.1:5004 check

You can view the configuration details and more information check this URL. Once you have configured HAProxy, its time to start the service:

$ sudo systemctl start haproxy
$ sudo systemctl enable haproxy

4. Configure Firewall

We will add the HAProxy to the CentOS 8 firewall and update the rules with the following commands:

$ sudo firewall-cmd --add-port=8088/tcp --permanent
$ sudo firewall-cmd --reload

5. Configure HAProxy Logging

To configure HAProxy standard logging edit /etc/rsyslog.conf and enable UDP Syslog reception on port 514:

$ sudo nano /etc/rsyslog.conf

...
# Provides UDP syslog reception
# for parameters see http://www.rsyslog.com/doc/imudp.html
module(load="imudp") # needs to be done just once
input(type="imudp" port="514")
...
*.info;mail.none;authpriv.none;cron.none,local2.none /var/log/messages
local2.* /var/log/haproxy.log
...

Then, save the configuration file and run the command below to check for any errors:

$ rsyslogd -N1
$ sudo systemctl restart rsyslog haproxy

6. Configure Apache X-Forwarded-For Logging on Backend Servers

Now we log in to the backend servers and configure Apache to log X-Forwarded-For headers. The default line we are changing is:

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

Edit this line such that it looks like:

...
LogFormat "\"%{X-Forwarded-For}i\" %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %b" common
...

Save the file and restart Apache:

$ apachectl configtest
$ sudo systemctl restart httpd

How to Test HAProxy Load Balancer ?

To verify that HAProxy is able to load balance the HTTP requests, navigate to the browser, and access HAProxy using either the hostname or IP address.

How to Restart HAProxy ?

After configuring either layer 4 or layer 7, restart HAProxy with the following command:

$ systemctl restart haproxy

A successful restart will result in no output, which means HAProxy is up and running with the changes you just implemented.

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