Advanced Node.js

Chapter 5: Performance Optimization

5.1 Profiling

Profiling helps identify performance bottlenecks in your Node.js applications.

// Using built-in profiler
// node --prof app.js
// Generates isolate-*.log file
// node --prof-process isolate-*.log

// Using Chrome DevTools
// node --inspect app.js
// Open chrome://inspect in Chrome

// Using clinic.js
// npm install -g clinic
// clinic doctor -- node app.js
// clinic flame -- node app.js
// clinic bubbleprof -- node app.js

5.2 Memory Profiling

// Heap snapshot
const v8 = require('v8');
const heapSnapshot = v8.writeHeapSnapshot('heap-${Date.now()}.heapsnapshot');

// Analyze in Chrome DevTools
// chrome://inspect -> Memory tab -> Load snapshot

// Memory usage monitoring
const used = process.memoryUsage();
for (let key in used) {
    console.log(`${key} ${Math.round(used[key] / 1024 / 1024 * 100) / 100} MB`);
}

5.3 CPU Profiling

// CPU profiling with perf
// perf record -e cycles:u -g -- node app.js
// perf report

// Using 0x (flamegraph generator)
// npm install -g 0x
// 0x app.js

5.4 Optimization Techniques

// 1. Use connection pooling
const pool = mysql.createPool({
    connectionLimit: 10,
    host: 'localhost',
    user: 'user',
    password: 'password',
    database: 'mydb'
});

// 2. Cache frequently accessed data
const NodeCache = require('node-cache');
const cache = new NodeCache({ stdTTL: 600 });

function getCachedData(key) {
    let data = cache.get(key);
    if (!data) {
        data = fetchDataFromDB(key);
        cache.set(key, data);
    }
    return data;
}

// 3. Use streaming for large data
// Instead of loading entire file into memory
fs.createReadStream('large-file.txt')
    .pipe(transformStream)
    .pipe(fs.createWriteStream('output.txt'));