HAProxy: Configure HTTP Load Balancer in CentOS 7

Load balancing refers to efficiently distributing incoming network traffic across a group of backend servers, also known as a server farm or server pool. Load Balancing improves the distribution of workloads across multiple computing resources. Using multiple components with load balancing instead of a single component may increase reliability and availability through redundancy.

Load Balancer is the device that perform Load Balancing. Hardware and software load balancers may have a variety of special features. The fundamental feature of a load balancer is to be able to distribute incoming requests over a number of backend servers in the cluster according to a scheduling algorithm.

In this post, we will configure a HTTP Load Balancer with HAProxy to distribute HTTP workload between two webservers.

 

Table of Contents:

• System Specification
• Configure HAProxy on CentOS 7
• Test HAProxy Configuration

 

System Specification:

We have two Apache Web Servers webserver-01.example.com and webserver-02.example.com and we want to configure a HTTP Load Balancer for them i.e. haproxy-01.example.com.

Hostname	haproxy-01.example.com	webserver-01.example.com	webserver-02.example.com
IP Address	192.168.116.30/24	192.168.116.31/24	192.168.116.32/24
Operating System	CentOS 7	CentOS 7	CentOS 7
Web Server	NA	Nginx	Nginx

 

Configure HAProxy on CentOS 7:

To ensure that our webservers are properly configured and browsable, open their URLs in a Browser.

I have set different index pages on both servers, to differentiate between servers, when we are accessing using the load balancer.

Connect to the haproxy-01.example.com and install HAProxy.

[root@haproxy-01 ~]# yum install -y haproxy
Loaded plugins: langpacks, product-id, subscription-manager
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
Resolving Dependencies
--> Running transaction check
---> Package haproxy.x86_64 0:1.5-0.3.dev22.el7 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package        Arch          Version                     Repository       Size
================================================================================
Installing:
 haproxy        x86_64        1.5-0.3.dev22.el7           localyum        696 k

Transaction Summary
================================================================================
Install  1 Package

Total download size: 696 k
Installed size: 2.2 M
Downloading packages:
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : haproxy-1.5-0.3.dev22.el7.x86_64                             1/1
  Verifying  : haproxy-1.5-0.3.dev22.el7.x86_64                             1/1

Installed:
  haproxy.x86_64 0:1.5-0.3.dev22.el7

Complete!

HAProxy has been installed.

Now configure rsyslog to handle HAProxy logs.

[root@haproxy-01 ~]# vi /etc/rsyslog.conf

Search and uncomment following lines.

$ModLoad imudp
$UDPServerRun 514

Add following directive in the same file.

# HAProxy Logging
local2.*        /var/log/haproxy.log

Save settings and exit.

Restart rsyslog service to apply changes.

[root@haproxy-01 ~]# systemctl restart rsyslog.service

Now configure HAProxy settings according to our environment.

[root@haproxy-01 ~]# vi /etc/haproxy/haproxy.cfg

Add following directives in this file.

# HAProxy Load Balancer for Apache Web Server
frontend http-balancer
 bind 192.168.116.30:80
 default_backend web-servers

backend web-servers
 mode http
 balance roundrobin
 stats enable
 stats auth admin:123
 server webserver-01 192.168.116.31:80 check
 server webserver-02 192.168.116.32:80 check

Save settings and exit.

Start and enable haproxy service.

[root@haproxy-01 ~]# systemctl start haproxy ; systemctl enable haproxy
ln -s '/usr/lib/systemd/system/haproxy.service' '/etc/systemd/system/multi-user.target.wants/haproxy.service'

Allow HTTP service through Linux firewall.

[root@haproxy-01 ~]# firewall-cmd --permanent --add-service=http
success
[root@haproxy-01 ~]# firewall-cmd --reload
success

 

Test HAProxy Configuration:

Open the URL of the haproxy-01.example.com in a browser.

You may observe that the HTTP request has been served by webserver-01.example.com. It shows that our Load Balancer has forwarded the request to this server.

Press F5 to refresh the webpage.

Since, we have configured the roundrobin balancing in HAProxy. Therefore, it forwards next request to alternate server. You can refresh webpage multiple times to observe the functionality.

To see the detailed statistics of the HAProxy. Browse to http://haproxy-01.example.com/haproxy?stats.

We have successfully configured a HTTP Load Balancer with HAProxy.