OpenTelemetry (OTel)

OpenTelemetry adalah standar open-source untuk observability: traces, metrics, dan logs. Vendor-neutral — data bisa dikirim ke Jaeger, Grafana, Datadog, dll.

Three Pillars of Observability

• Traces — Ikuti request dari awal sampai akhir melintasi service
• Metrics — Angka terukur: latency, error rate, throughput
• Logs — Event records dengan context

Tracing Concepts

// Trace = kumpulan spans
// Span = satu operasi (HTTP request, DB query, dll)

Trace: "POST /api/orders"
├── Span: API Gateway (2ms)
├── Span: Auth Middleware (5ms)
├── Span: OrderController.create (150ms)
│   ├── Span: DB: INSERT orders (30ms)
│   ├── Span: DB: UPDATE inventory (20ms)
│   └── Span: HTTP: POST payment-service (80ms)
└── Span: Response serialization (3ms)

Setup di Node.js

// tracing.js — load sebelum app code
import { NodeSDK } from "@opentelemetry/sdk-node";
import { getNodeAutoInstrumentations } from "@opentelemetry/auto-instrumentations-node";
import { OTLPTraceExporter } from "@opentelemetry/exporter-trace-otlp-http";

const sdk = new NodeSDK({
  traceExporter: new OTLPTraceExporter({
    url: "http://localhost:4318/v1/traces",
  }),
  instrumentations: [getNodeAutoInstrumentations()],
});

sdk.start();

Custom Spans

import { trace } from "@opentelemetry/api";

const tracer = trace.getTracer("order-service");

async function processOrder(order) {
  return tracer.startActiveSpan("processOrder", async (span) => {
    span.setAttribute("order.id", order.id);
    span.setAttribute("order.total", order.total);

    try {
      await validateOrder(order);
      await chargePayment(order);
      span.setStatus({ code: SpanStatusCode.OK });
    } catch (err) {
      span.setStatus({ code: SpanStatusCode.ERROR, message: err.message });
      throw err;
    } finally {
      span.end();
    }
  });
}