instrumentHTTP

Mon, 21 Sep 2026 15:16:28 +0000

instrumentHTTP

The instrumentHTTP function instruments the k6 HTTP module with additional headers. It transparently replaces each of the k6 http module functions with versions that automatically attach a baggage header(by default) to every request.

Instrumented functions include del, get, head, options, patch, post, put, and request.

This means that, to instrument the HTTP requests, you don’t need to rewrite any code. Instead, call the module once in the init context. For details about propagation, refer to About baggage header.

Parameters

Name	Type	Description
`generateHeaders`	`function(method, body, params) headersMap`	A function taking the request method, body and params and returning a map of headers that will be attached. By default adding baggage header as explained in the about baggage header

Example

This example demonstrates how to use the this library to instrument every HTTP request made in a script with baggage header.

import { check } from 'k6';
import pyroscope from 'https://jslib.k6.io/http-instrumentation-pyroscope/1.0.2/index.js';
import http from 'k6/http';

// instrumentHTTP will ensure that all requests made by the `http` module
// from this point forward will have a baggage context attached.
pyroscope.instrumentHTTP();

export default () => {
  // the instrumentHTTP call in the init context replaced
  // the `http` module with a version that will automatically
  // attach a baggage header to every request.
  const res = http.get('http://httpbin.org/get', {
    headers: {
      'X-Example-Header': 'instrumented/get',
    },
  });
};

Client

Mon, 21 Sep 2026 15:16:28 +0000

Client

Client is an HTTP client constructor that attaches baggage headers to its requests. Use the Client class to include a context in HTTP requests so that Grafana pyroscope can incorporate their results.

The Client class acts as a drop-in replacement for the standard http module and attaches a baggage header to the request. For details about propagation, refer to About baggage header.

The Client constructor accepts a function that takes the method, the body, and the params of each request and returns a map of headers to be added to the request. By default, it appends the baggage header with the info necessary for Grafana Cloud Profiling to integrate with Grafana Cloud k6.

For details about propagation, refer to About baggage header.

Example

This example demonstrates how to instantiate a client and use it to instrument HTTP calls. The example also illustrates how you can use the client alongside the standard http module to perform non-instrumented HTTP calls.

import { check } from 'k6';
import pyroscope from 'https://jslib.k6.io/http-instrumentation-pyroscope/1.0.2/index.js';
import http from 'k6/http';

// Explicitly instantiating a Pyroscope client allows to distinguish
// instrumented from non-instrumented HTTP calls, by keeping APIs separate.
const instrumentedHTTP = new pyroscope.Client();

const testData = { name: 'Bert' };

export default () => {
  // Using the pyroscope client instance, HTTP calls will have
  // baggage header added.
  let res = instrumentedHTTP.request('GET', 'http://httpbin.org/get', null, {
    headers: {
      'X-Example-Header': 'instrumented/request',
    },
  });

  // The client offers more flexibility over
  // the `instrumentHTTP` function, as it leaves the
  // imported standard `http` module untouched. Thus,
  // one can still perform non-instrumented HTTP calls
  // using it.
  res = http.post('http://httpbin.org/post', JSON.stringify(testData), {
    headers: { 'X-Example-Header': 'noninstrumented/post' },
  });

  res = instrumentedHTTP.del('http://httpbin.org/delete', null, {
    headers: { 'X-Example-Header': 'instrumented/delete' },
  });
};

HTTP module functions equivalents

The Client class exposes the same API as the standard http module except for the batch method, which is absent from Client. The following table lists the Client methods which have an equivalent in the standard http module:

Method	HTTP equivalent	Description
`Client.del(url, [body], [params])`	http.del	Performs an instrumented HTTP DELETE request. The method has the same prototype as the `http.del` function and should transparently act as a drop-in replacement for it.
`Client.get(url, [params])`	http.get	Performs an instrumented HTTP GET request. The method has the same prototype as the `http.get` function and should transparently act as a drop-in replacement for it.
`Client.head(url, [params])`	http.head	Performs an instrumented HTTP HEAD request. The method has the same prototype as the `http.head` function and should transparently act as a drop-in replacement for it.
`Client.options(url, [body], [params])`	http.options	Performs an instrumented HTTP OPTIONS request. The method has the same prototype as the `http.options` function and should transparently act as a drop-in replacement for it.
`Client.patch(url, [body], [params])`	http.patch	Performs an instrumented HTTP PATCH request. The method has the same prototype as the `http.patch` function and should transparently act as a drop-in replacement for it.
`Client.post(url, [body], [params])`	http.post	Performs an instrumented HTTP POST request. The method has the same prototype as the `http.post` function and should transparently act as a drop-in replacement for it.
`Client.put(url, [body], [params])`	http.put	Performs an instrumented HTTP HEAD request. The method has the same prototype as the `http.put` function and should transparently act as a drop-in replacement for it.
`Client.request(method, url, [body], [params])`	http.request	Performs an instrumented HTTP request. The method has the same prototype as the `http.request` function and should transparently act as a drop-in replacement for it.
`Client.asyncRequest(method, url, [body], [params])`	http.asyncRequest	Performs an instrumented HTTP asynchronous request. The method has the same prototype as the `http.asyncRequest` function and should transparently act as a drop-in replacement for it.

HTTP instrumentation for Pyroscope on Grafana Labs

instrumentHTTP

instrumentHTTP

Parameters

Example

Client

Client

Example

HTTP module functions equivalents