Custom Instrumentation

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

Distributed tracing will be set up automatically if:

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

If you're not using any of the packages above, take a look at the framework-specific Sentry integrations (like our Express integration). These integrations will also enable distributed tracing automatically for your application. If you can't find an integration for your framework, it is possible to set up distributed tracing for your application manually.

Enabling Distributed Tracing

If you set a tracesSampleRate (or enableTrace, or a tracesSampler function), distributed tracing will be enabled out of the box.

If you want to use distributed tracing, but not performance monitoring, set the tracesSampleRate option to 0. The default httpIntegration and nativeNodeFetchintegration will automatically instrument http and fetch requests.

Sentry.init({
  dsn: "https://examplePublicKey@o0.ingest.sentry.io/0",
  integrations: [],

  // Set this to 0 to enable distributed tracing without performance monitoring
  tracesSampleRate: 1,
});

Manually Extracing and Injecting Distributed Tracing Information

You can also manually extract and inject tracing data into your application. For this, you must:

• Extract and store incoming tracing information from incoming request headers or similar.
• Inject tracing information to any outgoing requests.

To learn more about distributed tracing, see our Distributed Tracing docs.

Extracting Incoming Tracing Information

You must extract and store incoming tracing information in memory for later use. Sentry provides the continueTrace() function to help you with this. Incoming tracing information can come from different places:

• In a web environment, it's sent with HTTP headers, for example, by another Sentry SDK used in your frontend project.
• In a job queue, it can be retrieved from meta or header variables.
• You also can pick up tracing information from environment variables.

Here's an example of how to extract and store incoming tracing information using continueTrace():

const http = require("http");

http.createServer((request, response) => {
  const sentryTraceHeaders = request.headers["sentry-trace"];
  const sentryTrace = Array.isArray(sentryTraceHeaders)
    ? sentryTraceHeaders.join(",")
    : sentryTraceHeaders;
  const baggage = request.headers["baggage"];

  Sentry.continueTrace(
    { sentryTrace, baggage },
    (transactionContext) => {
      Sentry.startSpan({
        ...transactionContext,
        name: "my request",
        op: "http.server",
      }, () => {
        // Your API code...
      });
    }
  );
});

In this example, we create a new transaction that is attached to the trace specified in the sentry-trace and baggage headers.

Inject Tracing Information to Outgoing Requests

For distributed tracing to work, the two headers that you extracted and stored in the requestTransaction, sentry-trace and baggage, must be added to outgoing http/fetch requests.

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

// Create `sentry-trace` header
const sentryTraceHeader = requestTransaction.toTraceparent();

// Create `baggage` header
const dynamicSamplingContext = requestTransaction.getDynamicSamplingContext();
const sentryBaggageHeader = dynamicSamplingContextToSentryBaggageHeader(
  dynamicSamplingContext
);

// 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.