Node.js + Apache Pulsar + Sentiment Analysis Example Application on Clever Cloud

This is a simple Node.js application that demonstrates how to use Apache Pulsar for message processing with sentiment analysis, and deploy it to Clever Cloud.

About the Application

This application displays a form where you can send a message. It assesses the mood of your message and tells if it's positive or negative. It uses:

• Apache Pulsar for message queuing between the server and worker
• Socket.IO for real-time communication with the client
• VADER for sentiment analysis (local, no external API needed)

How It Works

1. The client sends a message to the Express server
2. The server publishes the message onto an Apache Pulsar topic
3. A worker consumes the message, runs sentiment analysis, and publishes the result to another topic
4. The server reads the result and pushes it to the client via WebSocket

Endpoints

• GET / - Renders the main page with the message form
• POST /messages - Submit a message for sentiment analysis

Technology Stack

• Express.js 5 - Web framework for Node.js
• Socket.IO 4 - Real-time bidirectional communication
• pulsar-client - Apache Pulsar client for Node.js
• Tailwind CSS 4 - Utility-first CSS framework
• vader-sentiment - VADER sentiment analysis
• esbuild - JavaScript bundler
• Node.js 24+

Prerequisites

• Node.js 24+
• npm

Running the Application Locally

npm install
npm run build

Set the required environment variables (duplicate .env.example and fill the ADDON_PULSAR_ variables):

cp .env.example .env

You can either deploy a standalone Pulsar locally with Docker or use the Clever Cloud Pulsar add-on.

Start the server and worker:

npm start

# In another terminal
npm run worker

The application will be accessible at http://localhost:3000.

Deploying on Clever Cloud

You have two options to deploy your application on Clever Cloud: using the Web Console or using the Clever Tools CLI.

Option 1: Deploy using the Web Console

1. Create an account on Clever Cloud

If you don't already have an account, go to the Clever Cloud console and follow the registration instructions.

2. Set up your application on Clever Cloud

1. Log in to the Clever Cloud console
2. Click on "Create" and select "An application"
3. Choose "Node.js" as the runtime environment
4. Configure your application settings (name, region, etc.)

3. Add a Pulsar Add-on

1. In your application's dashboard, go to "Service dependencies"
2. Click "Link add-ons" and select "Pulsar"
3. Choose the plan that fits your needs
4. Link the add-on to your application

The ADDON_PULSAR_* environment variables will be automatically set.

4. Deploy Your Application

You can deploy your application using Git:

# Add Clever Cloud as a remote repository
git remote add clever git+ssh://git@push-par-clevercloud-customers.services.clever-cloud.com/app_<your-app-id>.git

# Push your code to deploy
git push clever master

Option 2: Deploy using Clever Tools CLI

1. Install Clever Tools

Install the Clever Tools CLI following the official documentation:

# Using npm
npm install -g clever-tools

# Or using Homebrew (macOS)
brew install clever-tools

2. Log in to your Clever Cloud account

clever login

3. Create a new application

# Initialize the current directory as a Clever Cloud application
clever create --type node <YOUR_APP_NAME>

# Add a Pulsar add-on
clever addon create addon-pulsar <YOUR_ADDON_NAME> --link <YOUR_APP_NAME>

4. Set environment variables

cat .env.prod.example | clever env import

5. Deploy your application

clever deploy

6. Open your application in a browser

Once deployed, you can access your application at the URL provided by Clever Cloud.

clever open

Monitoring Your Application

Once deployed, you can monitor your application through:

• Web Console: The Clever Cloud console provides logs, metrics, and other tools to help you manage your application.
• CLI: Use clever logs to view application logs and clever status to check the status of your application.

Additional Resources

• Express.js Documentation
• Apache Pulsar Documentation
• Socket.IO Documentation
• Clever Cloud Node.js Documentation
• Clever Cloud Pulsar Add-on Documentation
• Clever Cloud Documentation