V0.43.0

k6 v0.43.0 is here! :tada:

Notable changes in this release include:

xk6-browser is now bundled in k6 as an experimental module, and usable without a separate binary or compilation step!
Native support for JavaScript's async/await.
A new experimental module for distributed tracing.
Large refactoring of core components to simplify the code base, improve maintainability, and increase test coverage.
Bug fixes, UX improvements, and maintenance.

Keep reading for the details.

Breaking changes

#2807 Use non-zero exit codes for tests aborted by Ctrl+C or the REST API.

Aborting a test run with Ctrl+C will now exit with code 105, and stopping via the REST API will exit with code 103.

New Features

xk6-browser is now a built-in module #2884

This release includes xk6-browser as an experimental module. This means you can now also use the main k6 binary for browser automation and end-to-end testing, without needing to build a custom binary with xk6.

All xk6-browser scripts that work with v0.8.0 will continue to work with the built-in module in k6 v0.43.0. To use them, change the import path from k6/x/browser to k6/experimental/browser, and set the environment variable K6_BROWSER_ENABLED to true. The requirement to specify the environment variable is temporary and may be removed in a future k6 release. It was added to minimize the risks with k6 unexpectedly launching a browser (or another process) from k6 scripts. It's also a mechanism we use in the k6 Cloud, where browser tests are currently disabled.

For details, review the script example, or the updated browser module documentation.

The module is currently under the experimental namespace, which means we reserve the decision to introduce breaking changes in the future. However, our mid-term goal is to drop the experimental label and make browser support a stable part of the k6 feature set, eventually enabling it in k6 Cloud as well.

Native support for JavaScript's `async`/`await` #2830

In v0.35.0 we added support for asynchronous functionality in k6 scripts with the addition of Promise.

While useful, the experience wasn't very friendly. Scripts had to use the .then() API to chain Promises, instead of the await syntax available in most other JavaScript runtimes, and the async keyword wasn't supported. Some workarounds were possible, but it required a separate build pipeline to transpile the syntax into the older ES5.1+ standard supported by k6.

That is, until now! :tada: With invaluable help from @dop251, who maintains goja, the JS VM k6 uses, v0.43.0 brings native async/await to your k6 scripts. This functionality works just as you'd expect in other JS runtimes, and makes working with async APIs much more convenient. For details, review the following http.asyncRequest() example.

One caveat to note: async functions can't be passed to group() or check(). These functions are incompatible with asynchronous behavior, so you will get an error if trying to do so.

Experimental JavaScript module for distributed tracing #2853 #2854 #2855

This release brings a new experimental JavaScript module that adds distributed tracing support to k6. With one call in init context, you can instrument your test script's HTTP requests. If the system you're testing is instrumented in the same way, this module brings visibility to SUT behavior for the lifetime of each request.

An example:

javascript

import tracing from 'k6/experimental/tracing';
import http from 'k6/http';

tracing.instrumentHTTP({
  propagator: 'w3c',
});

export default () => {
  http.get('https://httpbin.test.k6.io/get', {
    headers: {
      'X-Example-Header': 'instrumented/get',
    },
  });
};

For details and examples, refer to the tracing module documentation.

`http.asyncRequest` #2877

The k6/http module has a new asyncRequest function that takes the same arguments as http.request(), but returns a Promise that, when used with await, will be resolved with a Response object. This gives you more control over script execution, as potentially the most time-consuming calls—making HTTP requests—will no longer block the thread of execution.

An example issuing a POST request:

javascript

import http from 'k6/http';

export default async function () {
  const resPromise = http.asyncRequest(
    'POST', 'https://httpbin.test.k6.io/post', { name: 'Bert' });
  // Do something else here, make other requests, etc.
  // Then when you're ready to use the response:
  const resp = await resPromise;
  console.log(resp.json().form.name); // Bert
}

This is one of the first steps towards migrating our APIs to be asynchronous, and similar changes can be expected in the future.

You can read more about asyncRequest in the documentation.

Enhancements and UX improvements

#2754, #2805 The output of the k6 version command has been enhanced to also show the version of all extensions built into the k6 binary produced by xk6. Thanks, @HarrisChu!
#2800 Improved handling of the Ctrl+C signal to gracefully abort the test during VU initialization.
#2803 Ensure the REST API server is shut down after the test ends.
#2867 Added the ability to display test run details and logs from k6 Cloud.
#2890 Added a method for JavaScript modules to lookup environment variables without directly accessing the os package.
#2910 Added a bit more context when parsing the script options, so that it is more obvious what fails.

Bug fixes

#2829 The csv output now correctly shows vu and iter system tags. This fixes a regression introduced in v0.40.0. Thanks, @leonyork!
#2851 Calling k6/execution.test.abort() within a group() now correctly exits the k6 process with code 108. Thanks for reporting this, @pomeh!
#2896 Fixed a panic in k6/ws when using Socket.setInterval() with values between 0 and 1.
#2903 Fixed a regression introduced in v0.42.0 where k6 will load the wrong module if the same import specifier has already been loaded, but they are pointing to different absolute paths, based on the files they are imported from.
#2907 Fixed the exit code and run_status value when the cloud output aborts a test.

Maintenance and internal improvements

#2809, #2810, #2812, #2813, #2815, #2885, #2893 A core component of test execution, the Engine, was removed, and the behavior heavily refactored. This change simplifies the code base and unblocks further improvements.
#2821, #2864 Our high-level integration test suite was refactored and expanded, increasing the coverage of behavior that closely replicates real-world usage.
#2803 Enabled checking for goroutine leaks.
#2883 The goja runtime has been updated.
#2845 Lint fixes in the k6/http module.
#2831 Compatibility with TC39 error messages was improved.
#2846 The initialization of js.Bundle was simplified.
#2861, #2870 Some deprecated features and dependencies in our CI pipeline were removed.
#2882 Our Dockerfile was improved with some linter suggestions. Thanks, @kempsterc!

Full Changelog: https://github.com/grafana/k6/compare/v0.42.0...v0.43.0