Node.js Process Management

What is Process Management?

It includes:

Starting and stopping applications

Restarting after crashes

Monitoring performance

Handling system signals

Managing environment variables

Accessing Process Information

Here are some useful properties:

console.log('Node.js version:', process.version);
// Memory usage (in bytes)
console.log('Memory usage:', process.memoryUsage());
// Command line arguments console.log('Arguments:', process.argv);

Exiting a Process

process.exit();
// Or explicitly process.exit(0);

process.exit(1);

// Run cleanup before exiting process.on('beforeExit', (code) => {
console.log('About to exit with code:', code);
});

Handling Process Events

1. Handling Ctrl + C (SIGINT)
// Handle Ctrl + C

process.on('SIGINT', () => {
console.log('\nGot SIGINT. Press Control-D to exit.');
// Perform cleanup if needed process.exit(0);

process.on('SIGTERM', () => {
console.log('Received SIGTERM. Cleaning up...');
// Perform cleanup if needed process.exit(0);
});

process.on('SIGTERM', () => {
console.log('Received SIGTERM. Cleaning up...');
server.close(() => {
console.log('Server closed');
process.exit(0);
});
});

3. Uncaught Exceptions process.on('uncaughtException', (err) => {
console.error('Uncaught Exception:', err);
// Perform cleanup if needed process.exit(1); // Exit with error
});

Process Managers

1. Install PM2 Globally npm install - g pm2

// ecosystem.config.js module.exports = {
apps: [{
name: 'my-app', script: 'app.js', instances: 'max', autorestart: true, watch: false, max_memory_restart: '1G', env: {
NODE_ENV: 'development',
}, env_production: {
NODE_ENV: 'production',
}
}]
};

Environment Variables

Environment variables are key - value pairs that configure your application's behavior in different environments.

Accessing Environment Variables

// Get a specific environment variable const apiKey = process.env.API_KEY;
// Set a default value if not defined const port = process.env.PORT || 3000;
// Check if running in production const isProduction = process.env.NODE_ENV === 'production';
// List all environment variables console.log('Environment variables:', process.env);

// Load environment variables from .env file require('dotenv').config();
// Now you can access variables from .env console.log('Database URL:', process.env.DATABASE_URL);

Best Practices for Environment Variables:

Never commit sensitive data to version control

Child Processes

1. Execute a Simple Command const { exec } = require('child_process');
exec('ls -la', (error, stdout, stderr) => {
if (error) {
console.error(`Error: ${error.message}`);
return;
}
if (stderr) {
console.error(`stderr: ${stderr}`);
return;
}
console.log(`Output: ${stdout}`);
});

2. Using spawn for Large Output const { spawn } = require('child_process');
// Better for large data output const child = spawn('find', ['/', '-type', 'f']);
child.stdout.on('data', (data) => {
console.log(`Found file: ${data}`);
});
child.stderr.on('data', (data) => {
console.error(`Error: ${data}`);
});
child.on('close', (code) => {
console.log(`Child process exited with code ${code}`);
});

Process Monitoring and Performance

// Get memory usage in MB function getMemoryUsage() {
const used = process.memoryUsage();
return {
rss: `${Math.round(used.rss / 1024 / 1024 * 100) / 100} MB`, heapTotal: `${Math.round(used.heapTotal / 1024 / 1024 * 100) / 100} MB`, heapUsed: `${Math.round(used.heapUsed / 1024 / 1024 * 100) / 100} MB`, external: `${Math.round(used.external / 1024 / 1024 * 100) / 100} MB`
};
}
// Monitor memory usage every 5 seconds setInterval(() => {
console.log('Memory usage:', getMemoryUsage());
}, 5000);

2. CPU Usage const startUsage = process.cpuUsage();
// Do some CPU-intensive work for (let i = 0; i < 1000000000; i++) {}
const endUsage = process.cpuUsage(startUsage);
console.log('CPU usage (user):', endUsage.user / 1000, 'ms');
console.log('CPU usage (system):', endUsage.system / 1000, 'ms');

Key Takeaways

Process Object

Process Control

Environment Variables

Child Processes

Error Handling