What is a Load Balancer?

When it comes to big companies, having a reliable IT setup that can grow, stay up and running, and perform well is really important. This is because they need to meet the needs of thousands or even millions of users at the same time. A load balancer is a key tool that helps with this. In this guide, we’ll explore what load balancers are, why they’re so important for large companies, and how to set them up for the best performance.

A load balancer is a tool, either a hardware device or a software program, that helps spread out incoming internet traffic among several servers. Its main goal is to make sure that one server doesn’t get overloaded with too many requests, which helps keep applications running smoothly and reliably. By sharing the workload, the system can manage lots of users at once, ensuring that services remain available and data can be accessed quickly.

Why Do Enterprises Need Load Balancers?

In big companies with many users, servers can get overwhelmed by too much traffic. When a single server gets too many requests, it can slow down or even crash. To solve this problem, load balancers help by spreading the incoming requests across several servers. This way, no single server gets too overloaded and everything keeps running smoothly.

Here’s why:

Types of Load Balancers

There are two main types of load balancers that big companies typically use:

Load Balancer Algorithms

Load balancers use different methods to decide how to spread out incoming traffic. Here are some of the most common ones:

• Round Robin: This is a straightforward method that sends requests evenly to all servers in a cycle. Think of it like passing the ball around in a circle.
• Least Connections: This method sends traffic to the server that is currently handling the fewest requests. It’s great for situations where some tasks take longer than others.
• IP Hash: With this method, the load balancer looks at the visitor’s IP address to determine which server should handle their request. This way, a user will always connect to the same server for their requests.
• Weighted Round Robin: This is similar to round robin but gives more requests to stronger, more capable servers. It means that if a server can handle more traffic, it gets more requests compared to other servers.

Configuring Load Balancing on Apache2 for a Large-Scale Enterprise

Example of an enterprise that has 5 web servers, and we want to distribute traffic across multiple backend servers.

First and must haves

1. Install Apache2 on Ubuntu/Debian:

sudo apt update
sudo apt install apache2

2. Enable the required modules for load balancing. Apache uses the mod_proxy, mod_proxy_balancer, and mod_proxy_http modules to handle load balancing

sudo a2enmod proxy
sudo a2enmod proxy_balancer
sudo a2enmod proxy_http

Step 2: Configure the Load Balancer in Apache

sudo nano /etc/apache2/sites-available/loadbalancer.conf

2. Add the following configuration to enable load balancing using round-robin method, which is the default method for distributing traffic evenly

<VirtualHost *:80>
    # Enable the load balancing mechanism
    ProxyRequests Off
    <Proxy balancer://mycluster>
        # Define the backend servers (add more as necessary)
        BalancerMember http://192.168.1.2:80
        BalancerMember http://192.168.1.3:80
        BalancerMember http://192.168.1.4:80
        BalancerMember http://192.168.1.5:80
        BalancerMember http://192.168.1.6:80

        # Load balancing method - round-robin (default)
        ProxySet lbmethod=byrequests

        # Optional: You can use the leastconn method to balance based on the least active connections
        # ProxySet lbmethod=bytraffic
    </Proxy>

    # Proxy all requests to the load balancer pool
    ProxyPass / balancer://mycluster/
    ProxyPassReverse / balancer://mycluster/

    # Logging for load balancing (optional)
    LogLevel warn
</VirtualHost>

sudo a2ensite loadbalancer.conf

sudo systemctl restart apache2

ProxySet stickysession=JSESSIONID

2. Health Checks: You can configure Apache to perform periodic health checks on the backend servers and avoid routing traffic to unhealthy servers

BalancerMember http://192.168.1.2:80 status=+H
BalancerMember http://192.168.1.3:80 status=+H
# Add more backend servers with health check status

3. SSL Termination: If you are handling HTTPS traffic, you can enable SSL termination on the load balancer by adding SSL configurations

<VirtualHost *:443>
    SSLEngine on
    SSLCertificateFile /path/to/your/certificate.crt
    SSLCertificateKeyFile /path/to/your/private.key

    ProxyPass / balancer://mycluster/
    ProxyPassReverse / balancer://mycluster/

    # Other SSL configurations...
</VirtualHost>

When Apache2 is set up correctly as a load balancer, it can manage large amounts of traffic by sharing requests across several backend servers. This helps businesses grow, stay available, and perform better, especially for big operations. The setup steps outlined will guide you on how to implement load balancing with Apache, offering different options like round-robin and keeping sessions active to match your business needs.

By making sure your load balancing is optimized, you can ensure that your web services stay available and reliable, even when there’s a lot of traffic.