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A Load Balancer is a critical technology designed to distribute incoming network traffic across multiple servers to ensure no single server is overwhelmed. This improves application scalability, performance, and availability. Load balancers also provide additional features such as service discovery, health checks, logging, and security.
They come in two forms:
- Hardware-based (physical devices)
- Software-based (e.g., Nginx, HAProxy)
- Cloud-based (AWS ELB, GCP Load Balancer, Azure Load Balancer)
Common Load Balancing Algorithms:
- Round Robin – Distributes requests sequentially to each server.
- Weighted Round Robin – Assigns weights to servers, directing more traffic to higher-capacity servers.
- Least Connections – Sends requests to the server with the fewest active connections.
- Response Time – Routes traffic based on the fastest server response time.
- IP Hash – Uses client IP hashing to ensure a client consistently connects to the same server.
- Resource-Based – Distributes load based on server resource availability (CPU, RAM).
You Should Know:
1. Setting Up Nginx as a Load Balancer
Nginx is a popular software load balancer. Here’s how to configure it:
Install Nginx (Ubuntu/Debian)
sudo apt update sudo apt install nginx -y
Configure Load Balancing (Round Robin)
Edit `/etc/nginx/nginx.conf`:
http {
upstream backend {
server 192.168.1.10;
server 192.168.1.11;
server 192.168.1.12;
}
server {
listen 80;
location / {
proxy_pass http://backend;
}
}
}
Restart Nginx:
sudo systemctl restart nginx
Weighted Load Balancing
upstream backend {
server 192.168.1.10 weight=3;
server 192.168.1.11 weight=2;
server 192.168.1.12 weight=1;
}
2. AWS Elastic Load Balancer (ELB) Setup
AWS provides three types of load balancers:
- Application Load Balancer (ALB) – HTTP/HTTPS traffic
- Network Load Balancer (NLB) – Ultra-low latency
- Classic Load Balancer (CLB) – Legacy
Create an ALB via AWS CLI
aws elbv2 create-load-balancer --name my-alb --subnets subnet-1234 subnet-5678 --security-groups sg-123456
Register Targets (EC2 Instances)
aws elbv2 register-targets --target-group-arn arn:aws:elasticloadbalancing:us-east-1:123456789012:targetgroup/my-targets/1234567890123456 --targets Id=i-1234567890abcdef0
3. Health Checks (Prevent Downtime)
Nginx health check configuration:
upstream backend {
server 192.168.1.10 max_fails=3 fail_timeout=30s;
server 192.168.1.11 max_fails=3 fail_timeout=30s;
}
AWS ALB Health Check:
aws elbv2 modify-target-group --target-group-arn arn:aws:elasticloadbalancing:us-east-1:123456789012:targetgroup/my-targets/1234567890123456 --health-check-path /health --health-check-interval-seconds 30
4. Load Balancing with HAProxy
Install HAProxy:
sudo apt install haproxy -y
Configure `/etc/haproxy/haproxy.cfg`:
frontend http-in bind :80 default_backend servers backend servers balance roundrobin server server1 192.168.1.10:80 check server server2 192.168.1.11:80 check
Restart HAProxy:
sudo systemctl restart haproxy
What Undercode Say:
Load balancing is a must-have for modern applications. Whether using Nginx, HAProxy, or cloud-based solutions like AWS ELB, distributing traffic efficiently prevents downtime and optimizes performance.
Key Takeaways:
✔ Use Round Robin for simple distribution.
✔ Apply Weighted Balancing for heterogeneous server capacities.
✔ Least Connections is ideal for long-lived sessions.
✔ Health Checks ensure only healthy servers receive traffic.
Expected Output:
A scalable, high-availability system with minimal downtime, improved response times, and efficient resource utilization.
Prediction:
As applications grow more complex, AI-driven load balancing (predictive scaling) will become standard, dynamically adjusting traffic based on real-time analytics.
Relevant URLs:
References:
Reported By: Maheshma Systemdesign – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
