Custom Instrumentation

On this page you will learn how to manually propagate trace information into and out of your JavaScript application.

Distributed tracing will be set up automatically if:

• You've Set Up Performance in Sentry.
• You're using one of the SDKs that include distributed tracing out of the box:
  • @sentry/nextjs
  • @sentry/sveltekit
  • @sentry/remix
  • @sentry/astro

If you are using a different package, and have not enabled performance monitoring, you can manually set up your application for distributed tracing to work.

Enabling Distributed Tracing

Inject Tracing Information to Outgoing Requests

For distributed tracing to work, the two headers that you extracted and stored in the active root span, sentry-trace and baggage, must be added to outgoing HTTP requests.

Here's an example of how to collect and inject this tracing information to outgoing requests:

const activeSpan = Sentry.getActiveSpan();
const rootSpan = activeSpan ? Sentry.getRootSpan(activeSpan) : undefined;

// Create `sentry-trace` header
const sentryTraceHeader = rootSpan
  ? Sentry.spanToTraceHeader(rootSpan)
  : undefined;

// Create `baggage` header
const sentryBaggageHeader = rootSpan
  ? Sentry.spanToBaggageHeader(rootSpan)
  : undefined;

// Make outgoing request
fetch('https://example.com', {
  method: 'GET',
  headers: {
    baggage: sentryBaggageHeader,
    'sentry-trace': sentryTraceHeader,
  },
}).then(response => {
  // ...
});

In this example, tracing information is propagated to the project running at https://example.com. If this project uses a Sentry SDK, it will extract and save the tracing information for later use.

The two services are now connected with your custom distributed tracing implementation.

Verification

If you make outgoing requests from your project to other services, check if the headers sentry-trace and baggage are present in the request. If so, distributed tracing is working.