Information

HAProxy is a free, very fast and reliable reverse-proxy offering high availability, load balancing, and proxying for TCP and HTTP-based applications. It is particularly suited for very high traffic web sites and powers a significant portion of the world’s most visited ones.

Over the years it has become the de-facto standard opensource load balancer, is now shipped with most mainstream Linux distributions, and is often deployed by default in cloud platforms

Step 1 – Update the system

Firstly update your system, on Debian you can use the below command.

apt-get update && apt upgrade -y

Step 2 – Installing HAProxy

Install HAProxy using apt-get

apt install haproxy

Check HAProxy is running.

systemctl status haproxy

Output:

● haproxy.service - HAProxy Load Balancer
     Loaded: loaded (/lib/systemd/system/haproxy.service; enabled; vendor preset: enabled)
     Active: active (running) since Sat 2023-01-21 06:03:21 GMT; 6s ago
       Docs: man:haproxy(1)

Step 2 – Configuring HAProxy for Load Balancing

We’ll start by removing the default configuration file, this can normally be found at /etc/haproxy/haproxy.cfg

rm /etc/haproxy/haproxy.cfg

Then create a new configuration file:

nano /etc/haproxy/haproxy.cfg

Paste the following into the file & change it suite your infrastructure:

defaults
    retries 3
    option  redispatch
    timeout client 30s
    timeout connect 4s
    timeout server 30s

frontend tcp_listner
 bind *:3128
 mode tcp
 default_backend tcp_backend_3128

backend tcp_backend_3128
 balance roundrobin
 mode tcp
 server infra-node1 10.0.0.1:1080 check
 server infra-node2 10.0.0.2:1080 check

For this example, I’m using port 3128 as the frontend listener which is then redirecting connections to two backends infra-node1 & infra-node1 on IP’s 10.0.0.1 & 10.0.0.2 using a roundrobin algorithm

Load Balancing Algorithms

The load balancing algorithm that is used determines which server, in a backend, will be selected when load balancing.

HAProxy offers several options for algorithms. In addition to the load balancing algorithm, servers can be assigned a weight parameter to manipulate how frequently the server is selected, compared to other servers.

You can explore the different types of load balancing algorithms here

roundrobin

Round Robin selects servers in turns. This is the default algorithm.

source

This selects which server to use based on a hash of the source IP address that users are making requests from. This method ensures that the same users will connect to the same servers.

leastconn

Selects the server with the least number of connections. This is recommended for longer sessions. Servers in the same backend are also rotated in a round-robin fashion.

Step 3 - Restart HA Proxy

You can now restart the HAProxy service & test your connection.

systemctl restart haproxy

Check the service is running again:

systemctl status haproxy

Output:

● haproxy.service - HAProxy Load Balancer
     Loaded: loaded (/lib/systemd/system/haproxy.service; enabled; vendor preset: enabled)
     Active: active (running) since Sat 2023-01-21 05:52:32 UTC; 23min ago
       Docs: man:haproxy(1)
             file:/usr/share/doc/haproxy/configuration.txt.gz
    Process: 863 ExecStartPre=/usr/sbin/haproxy -Ws -f $CONFIG -c -q $EXTRAOPTS (code=exited, status=0/SUCCESS)
   Main PID: 888 (haproxy)
      Tasks: 3 (limit: 1076)
     Memory: 72.4M
        CPU: 670ms
     CGroup: /system.slice/haproxy.service
             ├─888 /usr/sbin/haproxy -Ws -f /etc/haproxy/haproxy.cfg -p /run/haproxy.pid -S /run/haproxy-master.sock
             └─935 /usr/sbin/haproxy -Ws -f /etc/haproxy/haproxy.cfg -p /run/haproxy.pid -S /run/haproxy-master.sock

Jan 21 05:52:30 vps systemd[1]: Starting HAProxy Load Balancer...
Jan 21 05:52:32 vps haproxy[888]: [NOTICE]   (888) : New worker #1 (935) forked
Jan 21 05:52:32 vps systemd[1]: Started HAProxy Load Balancer.