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How do you handle instrumentation and observability in Next.js (instrumentation.ts)?

Q: How do you handle instrumentation and observability in Next.js (instrumentation.ts)?

**TL;DR.** instrumentation.ts exports a register() function that runs **once when the server starts** — the place to initialize **OpenTelemetry**, error monitoring (Sentry), or other tracing. Next.js also supports onRequestError and OpenTelemetry integration for **distributed tracing** across rendering and handlers. register() at server start OTel / Sentry init once</te

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Understand the problem

Startup hooks for tracing/monitoring.

nextjsinstrumentationobservabilityopentelemetry

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Read the code

Initialize tracing at startup

// instrumentation.ts (project root)
export async function register() {
  if (process.env.NEXT_RUNTIME === 'nodejs') {
    const { NodeSDK } = await import('@opentelemetry/sdk-node');
    new NodeSDK({ /* exporter, instrumentations */ }).start();
  }
}
// Optional: capture server errors with context
export async function onRequestError(err, request, context) {
  reportToSentry(err, { request, context });
}

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