Lesson 1: Load Balancers

What is a Load Balancer?

A load balancer sits between clients and servers, distributing incoming network traffic across a group of backend servers. This ensures that no single server bears too much load.

Types of Load Balancing

Layer 4 (Transport Layer)

• Decisions based on IP address and TCP/UDP ports.
• Faster, less CPU intensive.
• Does not inspect the content of the request.

Layer 7 (Application Layer)

• Decisions based on the content of the message (URL, HTTP headers, cookies).
• Can route traffic to different services based on URL (e.g., /images to image servers).
• More CPU intensive but smarter.

Algorithms

• Round Robin: Requests are distributed sequentially.
• Least Connections: Sends request to the server with the fewest active connections.
• IP Hash: The client’s IP address is used to determine which server receives the request (useful for session stickiness).

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🛠️ Sruja Perspective: Modeling Load Balancers

In Sruja, a load balancer is typically modeled as a container or component that sits in front of your application servers.

import { * } from 'sruja.ai/stdlib'


LB = container "Nginx Load Balancer" {
    technology "Nginx"
    tags ["load-balancer"]
    description "Layer 7 load balancer routing traffic based on URL paths."
}

AppServer = container "App Server" {
    technology "Python, Django"
    tags ["scaled"]
}

// Traffic flow
LB -> AppServer "Distributes requests (Round Robin)"

view index {
include *
}