Learn how to identify, diagnose, and fix memory leaks in Node.js applications using built-in profiling tools and best practices.
Memory leaks in Node.js applications can lead to degraded performance and eventual crashes. Understanding how to identify and fix them is crucial for production applications.
Common Causes of Memory Leaks
Global variables that grow indefinitely, forgotten timers and intervals, event listeners that aren't removed, closures holding onto large objects, and caching without limits are the most common culprits.
Using the Built-in Profiler
# Start your app with inspector
node --inspect server.js
# Or use the memory profiling flag
node --inspect --max-old-space-size=4096 server.jsOpen Chrome and navigate to chrome://inspect to connect to your Node.js process. Use the Memory tab to take heap snapshots and compare them over time.
Detecting Leaks Programmatically
const v8 = require('v8');
const fs = require('fs');
function takeHeapSnapshot(filename) {
const heapSnapshot = v8.writeHeapSnapshot(filename);
console.log(`Heap snapshot written to ${heapSnapshot}`);
}
// Take snapshots at different points
takeHeapSnapshot('./before.heapsnapshot');
// ... run your code ...
takeHeapSnapshot('./after.heapsnapshot');
// Compare snapshots using Chrome DevToolsMonitoring Memory Usage
function logMemoryUsage() {
const used = process.memoryUsage();
console.log({
rss: `${Math.round(used.rss / 1024 / 1024)}MB`,
heapTotal: `${Math.round(used.heapTotal / 1024 / 1024)}MB`,
heapUsed: `${Math.round(used.heapUsed / 1024 / 1024)}MB`,
external: `${Math.round(used.external / 1024 / 1024)}MB`
});
}
// Log every 10 seconds
setInterval(logMemoryUsage, 10000);Regular profiling, proper cleanup of event listeners, and implementing memory limits for caches are essential practices for preventing memory leaks in production Node.js applications.
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