Load Balancing with HAProxy

Introduction

HAProxy (High Availability Proxy) is a free, very fast, and reliable solution offering high availability, load balancing, and proxying for TCP and HTTP-based applications. In this tutorial, we will guide you through the steps to set up load balancing using HAProxy on a Linux system.

Prerequisites

Before we begin, ensure you have the following:

• A Linux server with root privileges
• Basic knowledge of Linux command line
• Multiple backend servers to load balance

Installing HAProxy

To install HAProxy on your Linux server, follow these steps:

Verify the installation by checking the HAProxy version:

Configuring HAProxy

HAProxy configuration file is located at /etc/haproxy/haproxy.cfg. Open this file with your preferred text editor:

The configuration file consists of several sections:

• global: Settings that apply to the entire HAProxy instance.
• defaults: Default settings that apply to all the proxies unless overridden.
• frontend: Defines how requests are received by HAProxy.
• backend: Defines how requests are forwarded to backend servers.

Example Configuration

Here's an example configuration for load balancing HTTP requests between two backend servers:

global
    log /dev/log local0
    log /dev/log local1 notice
    chroot /var/lib/haproxy
    stats socket /run/haproxy/admin.sock mode 660 level admin expose-fd listeners
    stats timeout 30s
    user haproxy
    group haproxy
    daemon

defaults
    log     global
    mode    http
    option  httplog
    option  dontlognull
    timeout connect 5000
    timeout client  50000
    timeout server  50000

frontend http_front
    bind *:80
    default_backend http_back

backend http_back
    balance roundrobin
    server server1 192.168.1.2:80 check
    server server2 192.168.1.3:80 check
                

In this configuration:

• The frontend section listens on port 80 and forwards requests to the backend section named http_back.
• The backend section named http_back uses a round-robin load balancing algorithm to distribute requests between server1 and server2.

Starting HAProxy

After configuring HAProxy, start the service using the following command:

Enable HAProxy to start on boot:

Check the status of HAProxy to ensure it is running correctly:

● haproxy.service - HAProxy Load Balancer
   Loaded: loaded (/lib/systemd/system/haproxy.service; enabled; vendor preset: enabled)
   Active: active (running) since Thu 2021-08-12 14:23:45 UTC; 5min ago
                

Testing HAProxy

To verify that HAProxy is correctly load balancing requests, you can use a web browser or a tool like curl to make requests to the HAProxy server:

Refresh the page or run the curl command multiple times to see the requests being distributed to the backend servers.

Conclusion

In this tutorial, you have learned how to install and configure HAProxy for load balancing HTTP requests across multiple backend servers. HAProxy is a powerful tool that can handle high traffic loads and provide high availability for your applications.