Documentation Grafana k6 JavaScript API jslib http-instrumentation-pyroscope Client

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.

JavaScript

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JavaScript Copy

import { check } from 'k6';
import pyroscope from 'https://jslib.k6.io/http-instrumentation-pyroscope/1.0.1/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: