WebSocket Horizontal Scaling Architecture

This project demonstrates an auto-scaling architecture for WebSocket servers running within a Kubernetes cluster, leveraging Prometheus metrics for dynamic scaling based on real-time usage.

Architecture Overview

The architecture is composed of several components designed to work in tandem for providing a scalable, real-time WebSocket communication service:

• websocket-client: A Node.js application that simulates WebSocket connections to test the scalability and performance of the WebSocket server.
• websocket-server: A Node.js WebSocket server that handles incoming connections and emits standard WebSocket events.
• websocket-scaler: A Python application running within the Kubernetes cluster, tasked with collecting metrics from the websocket-server pods and performing scaling actions based on those metrics.

Project Structure

The project is organized into the following directory structure:

• /apps
  • /websocket-client: Contains the WebSocket client simulation application.
  • /websocket-server: Contains the WebSocket server application.
  • /websocket-scaler: Contains the Kubernetes scaling application.
• /kubernetes
  • /redis: Contains Kubernetes manifests for Redis deployment, used for storing session data with persistence.
  • /websocket-server: Contains Kubernetes manifests for deploying the WebSocket server.
    • service.yaml: Service configuration with sessionAffinity: ClientIP to maintain session persistence.
    • ingress.ws: Ingress configuration with nginx.ingress.kubernetes.io/load-balance: "ewma" for efficient load balancing and nginx.ingress.kubernetes.io/upgrade: "websocket" to properly handle WebSocket upgrades.

Deployment

Prerequisites

Before deploying the WebSocket infrastructure, ensure that you have the following prerequisites installed:

• Minikube
• Helm

Minikube Installation and Setup

1. Install Minikube: Follow the official Minikube installation guide to install Minikube on your machine.

2. Start Minikube: Once installed, start a Minikube cluster using the following command:

   minikube start

3. Verify the cluster: Check the status of the cluster to ensure it's running:

   minikube status

Helm & Prometheus Installation and Setup

1. Fetch the script:

   curl -fsSL -o get_helm.sh https://raw.githubusercontent.com/helm/helm/main/scripts/get-helm-3

2. Add permisions to script:

   chmod 700 get_helm.sh

3. Execute the script:

   ./get_helm.sh

4. Add prometheus helm repository:

   helm repo add prometheus-community https://prometheus-community.github.io/helm-charts

5. Update helm repository:

   helm repo update

6. Install prometheus on minkube:

   helm install prometheus prometheus-community/kube-prometheus-stack

7. Verify prometheus installation: Ensure that all the components are up and running:

   kubectl get all -n prometheus

Deploying WebSocket Components

With Minikube and Prometheus running, you can now deploy the WebSocket components to the cluster:

1. Deploy Redis:: Navigate to the kubernetes/redis directory and apply the manifests:

   kubectl apply -f .

2. Deploy WebSocket Server:: Navigate to the kubernetes/websocket-server directory and apply the manifests for the StatefulSet and associated resources:

   kubectl apply -f .

3. Deploy WebSocket Scaler:: Navigate to the kubernetes/websocket-scaler directory and apply the manifests for the Deployment and associated resources:

   kubectl apply -f .

OBS: You can navigate to any app dir inside app/ and build your own docker image then change the image reference on StatefulSet or Deployment if you want to make any changes in the code, feel free :)

Usage

The connections.js script in the apps/websocket-client directory is a Node.js application that simulates multiple WebSocket connections to test the scalability and performance of the WebSocket server. It attempts to establish a specified number of WebSocket connections, each with a delay between connections to avoid overwhelming the server.

Running the WebSocket Client Simulation

To run the simulation, follow these steps:

1. Navigate to the Client Application Directory: Change into the apps/websocket-client directory where the connections.js script is located.

   cd apps/websocket-client

2. Install Dependencies:: Before running the script for the first time, make sure to install the necessary Node.js dependencies.

   npm install

3. Run the script:: Execute the connections.js script using Node.js.

   node src/connections.js