Version 0.51.0 release notes
k6 v0.51.0
is here 🎉! Some special mentions included in this release:
Breaking changes
Transition browser APIs to Async
In the last release notes we mentioned this breaking change, and we wanted to remind and update you on the plan. In the next release (v0.52.0), most of the synchronous browser APIs will be migrated to be asynchronous (promisifying them). We expect this will affect most if not all of our users.
This breaking change will require you to add await
in front of most of the browser module APIs. Without this await
you will witness undocumented and unknown behavior during the runtime. To make the migration simpler we advise that you work with the latest k6 type definitions.
You can find a list of all the APIs that we expect to convert to async in a comment in issue browser#428.
Awaiting on something that’s not a thenable just returns that value, which means you can add the await
keyword today on the APIs that will become async to future proof your test scripts.
Here are the reasons for making this large breaking change:
- Most browser APIs use some form of long-running IO operation (networking) to perform the requested action on the web browser against the website under test. We need to avoid blocking JavaScript’s runtime event loop for such operations.
- We’re going to add more asynchronous event-based APIs (such as page.on) that our current synchronous APIs would block.
- To align with how developers expect to work with JavaScript APIs.
- To have better compatibility with Playwright.
As a starting point, we have migrated a single API (the tap
method), which you can find the details below that will help visualize the upcoming breaking changes.
Browser Tap
is now an async method grafana/xk6-browser#1268
This release converts the Tap
method in the browser
module into an asynchronous method. This change is necessary to ensure that the method can be used in async contexts and to align with the rest of the browser module’s planned asynchronous API. To use the Tap
method, you must now add the await
keyword before the method call.
Affected components:
See the following example for how to use the Tap
method after this change:
Before:
import browser from 'k6/experimental/browser';
// ...
export default function () {
// ...
page.tap(selector, { modifiers: ['Alt', 'Control', 'Meta', 'Shift'] });
// ...
}
After:
import browser from 'k6/experimental/browser'
// ...
export default function () {
// ...
await page.tap(selector, { modifiers: ["Alt", "Control", "Meta", "Shift"] });
// ...
}
k6/experimental/websockets
will not default binaryType
to `“arraybuffer”'
As part of the stabilization of the API it needs to become as close to the specification.
Early in the development the idea of adding Blob
support as part was deemed feature creep and was dropped in favor of going with only "arraybuffer"
. But the specification defaults to returning binary responses as Blob
- which was another thing that was changed.
While adding Blob
is still on our radar, moving the default is always going to be a breaking change that we need to do to align with the specification.
For this release there is now a warning that will be printed if binaryType
is not set to "arraybuffer"
and a binary response is received. The warning will go away when binaryType
is set to "arraybuffer"
.
In the next release the warning will become an error.
More info and place for discussion can be found in an this issue.
k6/experimental/grpc
is no longer available #3530
As the last step of the graduation process for the experimental gRPC module, we completely removed the module. It is now fully integrated into the stable k6/net/grpc
module. So, if you haven’t done this yet, replace your imports from k6/experimental/grpc
to k6/net/grpc
.
Deprecations
The following pull requests start the process to introduce breaking changes. They are currently starting to emit warning if their condition is hit, but they will turn to return errors in the future release. It is recommended to use the suggested alternative, or to fix the script if you see the warning message.
- #3681 Use of not-compliant
require
expressions. - #3680 Modules resolution of modules not previously seen during the initialization phase.
- #3676 Working directory is set to the current location when the script is provided using stdin, instead of the root folder.
- #3530 Automagically resolve modules from cdnjs and github “URLs”.
New features
Introduction of k6/experimental/streams
module #3696
This release of k6 introduces the new k6/experimental/streams
module, which partially supports the JavaScript
Streams API, focusing initially on the ReadableStream
construct.
With the ReadableStream
, users can define and consume data streams within k6 scripts. This is particularly useful for
efficiently handling large datasets or for processing data sequentially in a controlled flow.
Expand to see an example of stream's usage
The following example demonstrates creating and consuming a simple stream that emits numbers until it reaches a predefined limit:
import { ReadableStream } from 'k6/experimental/streams';
function numbersStream() {
let currentNumber = 0;
return new ReadableStream({
start(controller) {
const fn = () => {
if (currentNumber < 5) {
controller.enqueue(++currentNumber);
setTimeout(fn, 1000);
return;
}
controller.close();
};
setTimeout(fn, 1000);
},
});
}
export default async function () {
const stream = numbersStream();
const reader = stream.getReader();
while (true) {
const { done, value } = await reader.read();
if (done) break;
console.log(`received number ${value} from stream`);
}
console.log('we are done');
}
For more advanced examples, please head to the MDN Web Docs on the Streams API.
Limitations
Currently, users can define and consume readable streams. However, this release does not include support for byte readers
and controllers, nor does it include support the tee
, pipeTo
, and
pipeThrough
methods of the ReadableStream
object.
New features and updates of WebCrypto API support #3714
This release brings support for asymmetric cryptography to the k6/experimental/webcrypto
module. We added support of the elliptic curves algorithms ECDH (xk6-webcrypto#67) and ECDSA (xk6-webcrypto#69) algorithms along with new import/export key formats like spki
and pkcs8
.
One of the newly added operations is deriveBits
, which allows parties to generate a unique shared secret by using shared public and non-shared private keys.
Expand to see an example of generating a shared secret for Alice and Bob.
The sign
and verify
operations got support for ECDSA algorithm. The sign
operation allows you to sign a message with a private key, while the verify
operation allows you to verify the signature with a public key.
Other notable updates and fixes:
- xk6-webcrypto#68 fixes a degradation for the sign/verify operations for HMAC algorithm.
- xk6-webcrypto#75, xk6-webcrypto#76 refactor webcrypto module to be thread-safe.
- xk6-webcrypto#74 adds JWK import/export support for ECDH and ECDSA. Refactors JWK import/export to use only go standard library.
See webcrypto’s module documentation for more details.
Timers globally available #3589
setTimeout
, setInterval
and related clear functions have been part of the JavaScript ecosystem, probably for as long as it has existed.
In the previous releases we stabilized and made them available through k6/timers
module. While the module isn’t going anywhere and might get more identifiers, setTimeout
is usually used without importing it. For this reason it is now globally available along clearTimeout
, setInterval
and clearInterval
.
No code needs to be changed, but you no longer need to import k6/timers
to use this functionality.
For a full list of changes, including UX improvements and bug fixes, refer to full release notes.