Getting Started with Tracing: A Guide for JavaScript Devs

Logs are great, metrics are helpful — but if you want to understand what your app is doing across systems, you need tracing. Traces give you the full journey of a request — from the client, through multiple microservices, databases, queues, and back. And as a JavaScript developer, you can (and should) start using it right now.

What is Tracing?

In simple terms, a trace is a timeline of what happened during a request. It's made up of spans — each span represents a unit of work (e.g., database query, HTTP call). When stitched together, they show exactly where time was spent.

  Trace ID: abc123xyz
  
  ┌── HTTP Request: /api/user/42
  │   ├── Span: Auth Middleware (15ms)
  │   ├── Span: DB query (80ms)
  │   └── Span: External API call (250ms)
  └── Total: 345ms
          

Why Should JS Devs Care?

JavaScript developers often work on async-heavy apps. Whether you're in Node.js or the browser, tracing helps:

• Debug slow requests across multiple services
• Catch unexpected retries or bottlenecks
• Understand app behavior across timeouts, queues, APIs

Getting Started with OpenTelemetry

OpenTelemetry is the go-to open-source standard for collecting and exporting traces. Here's how to instrument a basic Node.js app:

  // tracing.js
  const { NodeTracerProvider } = require('@opentelemetry/sdk-trace-node');
  const { SimpleSpanProcessor } = require('@opentelemetry/sdk-trace-base');
  const { JaegerExporter } = require('@opentelemetry/exporter-jaeger');
  
  const provider = new NodeTracerProvider();
  provider.addSpanProcessor(new SimpleSpanProcessor(new JaegerExporter()));
  provider.register();
          

Then, in your app:

  require('./tracing');
  
  const express = require('express');
  const app = express();
  
  app.get('/api/hello', (req, res) => {
    res.send('Hello World');
  });
  
  app.listen(3000);
          

What Tools Can You Use to Visualize?

Once your traces are flowing, you can visualize them in tools like:

• Jaeger – open-source trace viewer
• Honeycomb – flexible observability platform
• Grafana Tempo – integrates with Grafana dashboards

Common Gotchas

• 📛 Forgetting to propagate trace context across async calls
• 🔍 Too much detail — sampling is key
• 🧪 Not testing trace output in staging before production

Start Small, But Start Now

You don't have to trace everything today. Start with one critical endpoint. Get it flowing to Jaeger. Visualize. Then expand.

Tracing isn't just for SREs and backend teams. It's for anyone who wants to know what's really happening inside their apps — and that includes you.