❓ How?
Node.js handles concurrent requests using its single-threaded, event-driven architecture. Here’s a brief overview of how it works:
- Event Loop: Node.js operates on a single thread called the event loop. The event loop continually checks for tasks, executes them, and waits for new tasks to arrive. It handles I/O operations asynchronously, meaning it doesn't block the main thread.
- Non-blocking I/O: When an I/O operation is required (e.g., reading a file, querying a database), Node.js delegates the task to the underlying system. Node.js continues processing other tasks while waiting for the I/O operation to complete. When the I/O operation is done, a callback is added to the event loop, which processes it as soon as possible.
- Asynchronous Callbacks/Promises: Asynchronous operations in Node.js are often handled using callbacks, Promises, or async/await. These mechanisms allow Node.js to perform non-blocking I/O operations efficiently.
Good Practices to Keep in Mind
- Use Asynchronous Methods: Always prefer asynchronous versions of functions for I/O operations (e.g.,
fs.readFileinstead offs.readFileSync). This prevents the event loop from being blocked, allowing Node.js to handle other requests concurrently.
javascript
// Asynchronous file read
const fs = require('fs');
fs.readFile('example.txt', 'utf8', (err, data) => {
if (err) {
console.error(err);
return;
}
console.log(data);
});
2. Leverage Clustering: Node.js can run multiple instances of an application on different CPU cores using the Cluster module. This helps distribute the load and improves the application's ability to handle concurrent requests.
```javascript
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();
}
} else {
http.createServer((req, res) \=> {
res.writeHead(200);
res.end('Hello World');
}).listen(8000);
}
```
Pitfalls to Avoid
- Blocking the Event Loop: Avoid using synchronous methods or performing CPU-intensive operations directly in the event loop. These actions can block the event loop, making Node.js unable to handle other requests.
javascript
// Blocking example (avoid)
const fs = require('fs');
const data = fs.readFileSync('example.txt', 'utf8'); // Blocks the event loop
console.log(data);
2. Callback Hell: Deeply nested callbacks (callback hell) make the code hard to read and maintain. Use Promises or async/await to manage asynchronous operations more cleanly.
```javascript
// Callback Hell (avoid)
asyncOperation1(() \=> {
asyncOperation2(() \=> {
asyncOperation3(() \=> {
// and so on...
});
});
});
// Using Promises
asyncOperation1()
.then(() \=> asyncOperation2())
.then(() \=> asyncOperation3())
.catch(err \=> console.error(err));
// Using async/await
async function performOperations() {
try {
await asyncOperation1();
await asyncOperation2();
await asyncOperation3();
} catch (err) {
console.error(err);
}
}
```