Solving High CPU Usage for Node.js App on AWS

Step 1: Identify the Problem

First, we need to confirm that your Node.js app is causing high CPU usage. You can use CloudWatch to monitor CPU usage:

1. Log in to your AWS Management Console.
2. Navigate to the CloudWatch dashboard.
3. Click on Alarms and create an alarm to notify you when CPU usage goes above a certain threshold (e.g., 80%).

Step 2: Check Your Code

Sometimes, high CPU usage is due to inefficient code. Here are some common causes and fixes:

1. Infinite Loops: Ensure there are no infinite loops in your code.
2. Heavy Computations: Break down heavy computations or move them to a background job.
3. Blocking Code: Use asynchronous functions to avoid blocking the main thread.

Step 3: Optimize Your Node.js App

Make your app more efficient:

1. Use Clustering: Clustering allows you to use multiple CPU cores to handle multiple requests. Add the following to your main file (e.g., app.js):

   const cluster = require('cluster');
   const http = require('http');
   const numCPUs = require('os').cpus().length;
   
   if (cluster.isMaster) {
     for (let i = 0; i < numCPUs; i++) {
       cluster.fork();
     }
   
     cluster.on('exit', (worker, code, signal) => {
       console.log(`Worker ${worker.process.pid} died`);
     });
   } else {
     // Your server code here
     http.createServer((req, res) => {
       res.writeHead(200);
       res.end('Hello world\n');
     }).listen(8000);
   }

2. Optimize Dependencies: Ensure you're using the latest, most efficient versions of your dependencies.
3. Use Caching: Cache frequently accessed data to reduce load on your app.

Step 4: Scale Your Infrastructure

If your app is still experiencing high CPU usage, it might be time to scale your infrastructure:

1. Increase Instance Size: Move to a larger EC2 instance with more CPU power.
2. Load Balancing: Use an Elastic Load Balancer (ELB) to distribute traffic across multiple instances.
3. Auto Scaling: Set up Auto Scaling to automatically add more instances when CPU usage is high and reduce them when it’s low.

Step 5: Monitor and Maintain

Regularly monitor your app's performance using CloudWatch and other monitoring tools. Set up alerts to notify you of high CPU usage so you can address issues promptly.

Summary

By following these steps, you can identify the cause of high CPU usage in your Node.js app and take appropriate actions to fix it. This will help ensure your app runs smoothly and efficiently on AWS.