How to Monitor Memory Usage in Your Node.js Application

Understanding how much memory your Node.js application consumes is essential for optimizing performance and preventing memory leaks. Node.js provides built-in tools to check memory usage programmatically, and there are also external tools for real-time monitoring.

1. Using process.memoryUsage()

The process.memoryUsage() method in Node.js provides detailed information about the memory consumption of the current process. Here's a basic example:

console.log('Memory usage:', process.memoryUsage());

This will output an object with the following fields:

• rss: Resident Set Size - total memory used by the process, including code, data, and allocated memory.
• heapTotal: Total memory allocated for the JavaScript heap.
• heapUsed: Memory currently used by JavaScript objects.
• external: Memory used by C++ objects bound to Node.js.

An example output:

{
  "rss": 33157120,
  "heapTotal": 7385088,
  "heapUsed": 4812560,
  "external": 8272
}

2. Formatting Memory Usage for Readability

To make the output more user-friendly, you can format the values in megabytes:

function formatMemoryUsage(memory) {
    return {
        rss: `${(memory.rss / 1024 / 1024).toFixed(2)} MB`,
        heapTotal: `${(memory.heapTotal / 1024 / 1024).toFixed(2)} MB`,
        heapUsed: `${(memory.heapUsed / 1024 / 1024).toFixed(2)} MB`,
        external: `${(memory.external / 1024 / 1024).toFixed(2)} MB`
    };
}

console.log('Memory usage:', formatMemoryUsage(process.memoryUsage()));

3. Real-Time Memory Monitoring

If you'd like to monitor memory usage in real time, you can set up a periodic log using setInterval:

setInterval(() => {
    console.log('Memory usage:', formatMemoryUsage(process.memoryUsage()));
}, 5000); // Every 5 seconds

4. Monitoring Memory Usage Externally

For cases where you want to check memory usage from another terminal or without modifying your code, here are some options:

4.1. Using System Commands

On Linux/Unix:

ps aux | grep node
top -p <PID>

On Windows:

tasklist | findstr node

Then, you can monitor memory usage with tools like top, htop, or the Task Manager on Windows.

4.2. Using the pidusage Library

The pidusage package is a convenient tool to track memory and CPU usage for any Node.js process. Install it with:

npm install pidusage

Here's an example usage:

import pidusage from 'pidusage';

setInterval(async () => {
    const stats = await pidusage(process.pid);
    console.log(`Memory: ${(stats.memory / 1024 / 1024).toFixed(2)} MB`);
}, 5000);

Conclusion

To monitor memory usage effectively:

• Use process.memoryUsage() for built-in insights into your application's memory consumption.
• Format the output for better readability if needed.
• For real-time monitoring, leverage periodic logging or external tools like pidusage, top, or htop.

These techniques can help you keep your Node.js applications optimized and prevent memory issues from impacting performance.