DocumentationGrafana k6JavaScript APIjslibhttp-instrumentation-tempo

HTTP instrumentation for Tempo

With this jslib, you can instrument HTTP requests so that they emit traces as the test runs. Use it to include a tracing context in HTTP requests, which can then be used by a tracing backend such as Grafana Tempo.

About trace contexts

A trace context is a set of standardized HTTP headers added to a request that lets a tracing system correlate it with other requests as they navigate through a system. The trace context specifications, such as the supported W3C Trace Context and Jaeger Trace Context, define specific header names and an encoding format for the header values.

A trace context generally consists of, at least, a trace_id, a span_id, and a sampled flag. The trace_id is a unique identifier for the trace, the span_id is a unique identifier for the request, and the sampled flag is a boolean that indicates whether the request should be traced. For instance, the W3C Trace Context defines the Traceparent header, whose value contains a trace_id, a span_id and a sampled flag, encoded as a dash (-) separated list of hexadecimal values. When a trace context header is attached to an HTTP request, we refer to it as being propagated to the downstream service.

API

Example

This example demonstrates how to use the tracing API to instrument every HTTP request made in a script with tracing information.

JavaScript

Copy

JavaScript Copy

import { check } from 'k6';
import tempo from 'https://jslib.k6.io/http-instrumentation-tempo/1.0.0/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 trace context attached.
//
// The first argument is a configuration object that
// can be used to configure the tracer.
tempo.instrumentHTTP({
  // possible values: "w3c", "jaeger"
  propagator: 'w3c',
});

export default () => {
  // the instrumentHTTP call in the init context replaced
  // the http module with a version that will automatically
  // attach a trace context to every request.
  //
  // Because the instrumentHTTP call was configured with the
  // w3c trace propagator, this request will as a result have
  // a `traceparent` header attached.
  const res = http.get('http://httpbin.org/get', {
    headers: {
      'X-Example-Header': 'instrumented/get',
    },
  });
};