Monitoring Node.js: Key Metrics You Should Track

Summary

Effective Node.js monitoring requires tracking runtime metrics (memory, CPU), application metrics (request rates, response times), and business metrics (user actions, conversion rates). This guide covers what to track, how to collect it, and how to set up meaningful alerts.Why Do Node.js Metrics Matter?You've built a Node.js application and deployed it to production. Without proper metrics, troubleshooting becomes difficult when users report that "the app feels slow."Good metrics transform vague complaints into actionable data points like "the payment service is experiencing 500ms response times, up from a 120ms baseline."What Runtime Metrics Should You Track?Runtime metrics show how Node.js itself is performing. They provide early warning signs of problems.Monitor Memory UsageNode.js memory management and garbage collection can be tricky. Watch these metrics to identify memory issues:Heap Used vs Heap Total: When used memory grows without returning to baseline after garbage collection, you may have a memory leak.External Memory: Memory used by C++ objects bound to JavaScript objects.Garbage Collection Frequency: Frequent garbage collection can reduce performance.RSS (Resident Set Size): Total memory allocated for the Node process in RAM.Full GC Per Min: Number of full garbage collection cycles per minute.Incremental GC Per Min: Number of incremental garbage collection cycles per minute.Heap Size Changed: Percentage of memory reclaimed by garbage collection cycles.GC Duration: Time spent in garbage collection (longer durations impact performance).// Basic way to log memory usage in your app const logMemoryUsage = () => { const memUsage = process.memoryUsage(); console.log({ rss: `${Math.round(memUsage.rss / 1024 / 1024)} MB`, heapTotal: `${Math.round(memUsage.heapTotal / 1024 / 1024)} MB`, heapUsed: `${Math.round(memUsage.heapUsed / 1024 / 1024)} MB`, external: `${Math.round(memUsage.external / 1024 / 1024)} MB` }); };Measure CPU UtilizationNode.js is single-threade...