Node Test Restart

A Node.js test application demonstrating the forever-monitor NPM package's automatic process restart capabilities. This project creates a simple HTTP server that deliberately exits to showcase how forever-monitor detects crashes and restarts the process automatically.

Built in November 2020. This application helps developers understand how to implement automatic process restart and recovery in Node.js applications.

Features

• 🔄 Automatic process restart on crash/exit
• 📊 Restart counter tracking
• 🎯 Configurable restart limits
• 🚦 Exit code-based restart control
• ⚙️ Simple HTTP server for testing
• 📝 Error handling and logging

Getting Started

Prerequisites

• Node.js (v8 or higher)
• npm or yarn

Installation

1. Clone the repository:

git clone https://github.com/orassayag/node-test-restart.git
cd node-test-restart

2. Install dependencies:

npm install

Quick Start

Run the monitor to see automatic restarts in action:

npm start

The server will:

1. Start on port 3001
2. Exit after 1 second with code 2
3. Automatically restart (up to 10 times)
4. Display restart count each time

How It Works

Architecture Diagram

graph TD
    A[npm start] --> B[monitor.js]
    B --> C[Forever Monitor]
    C --> D[Start server.js]
    D --> E[HTTP Server Running]
    E --> F[Server exits after 1s]
    F --> G{Exit Code?}
    G -->|Code 1| H[Stop - No Restart]
    G -->|Code 2| I{Max Restarts?}
    I -->|Not Reached| J[Increment Counter]
    J --> D
    I -->|Reached| K[Stop Monitor]
    
    style A fill:#e1f5ff
    style C fill:#fff3cd
    style E fill:#d4edda
    style H fill:#f8d7da
    style K fill:#f8d7da

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Process Flow

1. Monitor Initialization: monitor.js creates a forever-monitor instance
2. Server Start: Monitor spawns server.js process
3. HTTP Server: Server listens on configured port (default: 3001)
4. Deliberate Exit: After 1 second, server exits with code 2
5. Monitor Detection: Forever-monitor detects the exit
6. Restart Decision: Based on exit code and restart count
7. Process Restart: Monitor restarts the server with incremented counter
8. Repeat: Process continues until max restarts reached

Exit Code Behavior

Exit Code	Behavior
1	Monitor stops - no restart
2 or other	Monitor restarts process automatically
Max reached	Monitor stops regardless of exit code

Configuration

Edit src/settings/settings.js:

const settings = {
    NODE_ENV: 'development',      // Environment mode
    SERVER_PORT: '3001'            // HTTP server port
};

Edit src/monitor.js:

const child = new (forever.Monitor)('server.js', {
    max: 10,              // Maximum number of restarts
    silent: false,        // Show/hide output
    args: [restartCount]  // Arguments passed to server
});

Available Scripts

Start Monitor

npm start

Starts the forever-monitor which automatically restarts the server.

Stop All Node Processes (Windows)

npm run stop

Forcefully stops all Node.js processes using taskkill.

Debug Mode

npm run debug

Starts the server with Node.js inspector for debugging.

Project Structure

node-test-restart/
├── src/
│   ├── monitor.js           # Forever-monitor configuration
│   ├── server.js            # HTTP server (exits deliberately)
│   ├── settings/
│   │   └── settings.js      # Configuration settings
│   └── services/
│       └── error.service.js # Error handling utilities
├── server.js                # Entry point
├── package.json
└── README.md

Testing Scenarios

Scenario 1: Normal Restart

1. Run npm start
2. Observe server starting, exiting, and restarting
3. Restart counter increments with each restart

Scenario 2: Max Restarts Limit

1. Change max: 3 in src/monitor.js
2. Run npm start
3. Monitor stops after 3 restarts

Scenario 3: Exit Code 1 (No Restart)

1. Change process.exit(2) to process.exit(1) in src/server.js
2. Run npm start
3. Monitor does NOT restart the server

Scenario 4: Custom Port

1. Change SERVER_PORT in src/settings/settings.js
2. Run npm start
3. Server starts on the new port

Development

The project uses:

• JavaScript (Node.js) with ES6+ features
• forever-monitor for process management
• death for graceful process termination
• ESLint for code quality

Use Cases

This pattern is useful for:

• Production servers: Automatic recovery from crashes
• Long-running processes: Keep services alive
• Development testing: Test restart/recovery logic
• Microservices: Ensure service availability
• Background jobs: Auto-restart failed workers

Common Issues

Port Already in Use

If port 3001 is in use:

• Change SERVER_PORT in settings
• Or stop the conflicting process
• On Windows: npm run stop

Monitor Won't Stop

• Press Ctrl+C to stop
• On Windows: npm run stop
• Check silent: false for visibility

No Console Output

• Set silent: false in src/monitor.js
• Run with npm start not node server.js

Contributing

Contributions to this project are released to the public under the project's open source license.

Everyone is welcome to contribute. Contributing doesn't just mean submitting pull requests—there are many different ways to get involved, including answering questions and reporting issues.

Please feel free to contact me with any question, comment, pull-request, issue, or any other thing you have in mind.

Author

• Or Assayag - Initial work - orassayag
• Or Assayag orassayag@gmail.com
• GitHub: https://github.com/orassayag
• StackOverflow: https://stackoverflow.com/users/4442606/or-assayag?tab=profile
• LinkedIn: https://linkedin.com/in/orassayag

License

This application has an MIT license - see the LICENSE file for details.