k6 v0.48.0 is here 🎉! This release includes:

• Numerous long-awaited breaking changes.
• A new k6 new subcommand to generate a new test script.
• A new k6/experimental/fs module for file interactions.
• CPU and network throttling support for the k6 browser module.

Breaking changes

This release includes several breaking changes, mainly cleaning up deprecations from previous versions. They should have a straightforward migration process, and not heavily impact existing users.

• #3448 limits metric names, aligning to both OpenTelemetry (OTEL) and Prometheus name requirements, while still being limited to 128 ASCII characters. Warnings about the limit started in v0.45.
• #3439 changes the Client signature in k6/experimental/redis module. Refer to the module-related section below.
• #3350 removes the grpc.invoke()'s parameter headers, deprecated in k6 v0.37. Use the metadata parameter instead.
• #3389 removes the --logformat flag, deprecated in v0.38. Use the --log-format flag instead.
• #3390 removes all CSV output's CLI arguments, deprecated in v0.35. This change makes the CSV output consistent with other output formats.
• #3365 removes the k6 convert CLI command, deprecated in v0.41. Use the har-to-k6 package instead.
• #3451 removes logic that would attempt to prepend a https:// scheme to module specifiers that were not recognized. Deprecated in k6 v0.25. Use full URLs if you want to load remote modules instead.

New features

Add k6 new subcommand #3394

k6 now has a new subcommand that generates a new test script. This is useful for new users who want to get started quickly, or for experienced users who want to save time when creating new test scripts. To use the subcommand, open your terminal and type:

k6 new [filename]

If no filename is provided, k6 uses script.js as the default filename. The subcommand will create a new file with the provided name in the current directory, and populate it with a basic test script that can be run with k6 run.

Add a k6/experimental/fs module #3165

k6 now has a new k6/experimenal/fs module providing a memory-efficient way to handle file interactions within your test scripts. It currently offers support for opening files, reading their content, seeking through it, and retrieving metadata about them.

Unlike the traditional open function, which loads a file multiple times into memory, the filesystem module reduces memory usage by loading the file as little as possible, and sharing the same memory space between all VUs. This approach significantly reduces the memory footprint of your test script and lets you load and process large files without running out of memory.

For more information, refer to the module documentation.

import fs from 'k6/experimental/fs';

// k6 doesn't support async in the init context. We use a top-level async function for `await`.
//
// Each Virtual User gets its own `file` copy.
// So, operations like `seek` or `read` won't impact other VUs.
let file;
(async function () {
  file = await open('bonjour.txt');
})();

export default async function () {
  // About information about the file
  const fileinfo = await file.stat();
  if (fileinfo.name != 'bonjour.txt') {
    throw new Error('Unexpected file name');
  }

  const buffer = new Uint8Array(128);

  let totalBytesRead = 0;
  while (true) {
    // Read into the buffer
    const bytesRead = await file.read(buffer);
    if (bytesRead == null) {
      // EOF
      break;
    }

    // Do something useful with the content of the buffer
    totalBytesRead += bytesRead;

    // If bytesRead is less than the buffer size, we've read the whole file
    if (bytesRead < buffer.byteLength) {
      break;
    }
  }

  // Check that we read the expected number of bytes
  if (totalBytesRead != fileinfo.size) {
    throw new Error('Unexpected number of bytes read');
  }

  // Seek back to the beginning of the file
  await file.seek(0, SeekMode.Start);
}

Redis (m)TLS support and new Client constructor options #3439, xk6-redis/#17

In this release, the k6/experimental/redis module receives several important updates, including breaking changes.

Connection URLs

The Client constructor now supports connection URLs to configure connections to Redis servers or clusters. These URLs can be in the format redis://[[username][:password]@][host][:port][/db-number] for standard connections, or rediss://[[username][]:password@]][host][:port][/db-number] for TLS-secured connections. For more details, refer to the documentation.

Example usage

import redis from 'k6/experimental/redis';

const redisClient = new redis.Client('redis://someusername:somepassword@localhost:6379/0');

Revamped Options object

The Client constructor has been updated with a new Options object format. This change aligns the module with familiar patterns from Node.js and Deno libraries, offering enhanced flexibility and control over Redis connections. For more details, refer to the documentation.

import redis from 'k6/experimental/redis';

const redisClient = new redis.Client({
  socket: {
    host: 'localhost',
    port: 6379,
  },
  username: 'someusername',
  password: 'somepassword',
});

(m)TLS support

The Redis module now includes (m)TLS support, enhancing security for connections. This update also improves support for Redis clusters and sentinel modes (failover). For connections using self-signed certificates, enable k6's insecureSkipTLSVerify option (set to true).

import redis from 'k6/experimental/redis';

const redisClient = new redis.Client({
  socket: {
    host: 'localhost',
    port: 6379,
    tls: {
      ca: [open('ca.crt')],
      cert: open('client.crt'), // client certificate
      key: open('client.key'), // client private key
    },
  },
});

Add tracing instrumentation #3445

k6 now supports a new traces output option that allows you to configure the output for traces generated during its execution. This option can be set through the --traces-output argument in the k6 run command or by setting the K6_TRACES_OUTPUT environment variable.

Currently, no traces are generated by k6 itself, but this feature represents the first step towards richer tracing functionalities in k6 and its extensions.

By default traces output is set to none, and currently the only supported output is otel which uses the opentelemetry-go's Open Telemetry API and SDK implementations. The format for the otel traces output configuration is the following:

--traces-output=<endpoint>[,opt1=val1,opt2=val2]

Where opts can be one of the following options:

• proto: Specifies the protocol to use in the connection to the traces backend. Supports grpc (default) and http.
• header.<header_name>: Specifies an additional header to include in the connection to the traces backend.

Example:

K6_TRACES_OUTPUT=https://traces.k6.io/v1/traces,proto=http,header.Authorization=Bearer token

Add support for browser module's page.throttleCPU browser#1095

The browser module now supports throttling the CPU from chrome/chromium's perspective by using the throttleCPU API, which helps emulate slower devices when testing the website's frontend. It requires an argument of type CPUProfile, which includes a rate field that is a slow-down factor, where 1 means no throttling, 2 means 2x slowdown, and so on. For more details, refer to the documentation.

...
  const context = browser.newContext();
  const page = context.newPage();

  try {
    page.throttleCPU({ rate: 4 });
...

Add support for browser module's page.throttleNetwork browser#1094

The browser module now supports throttling the characteristics of the network from chrome/chromium's perspective by using the throttleNetwork API, which helps emulate slow network connections when testing the website's frontend. It requires an argument of type NetworkProfile, with a definition of:

export interface NetworkProfile {
    /*
     * Minimum latency from request sent to response headers received (ms).
     */
    latency: number;
    
    /*
     * Maximal aggregated download throughput (bytes/sec). -1 disables download
     * throttling.
     */
    download: number;
    
    /*
     * Maximal aggregated upload throughput (bytes/sec). -1 disables upload
     * throttling.
     */
    upload: number;
}

You can either define your own network profiles or use the ones we have defined by importing networkProfiles from the browser module. For more details, refer to the documentation.

import { browser, networkProfiles } from 'k6/experimental/browser';
...
  const context = browser.newContext();
  const page = context.newPage();

  try {
    page.throttleNetwork(networkProfiles['Slow 3G']);
...

k6's documentation is moving under grafana.com/docs/k6

It's not directly part of the k6 v0.48 release, but we believe it is worth mentioning that we're moving the documentation from k6.io/docs to grafana.com/docs/k6.

The legacy documentation space k6.io/docs will be available for a while, but we encourage you to update your bookmarks and links to the new domain.

UX improvements and enhancements

• browser#1074 adds a new browser.closeContext() method to facilitate closing the current active browser context.
• #3370 adds a new flag --profiling-enabled which enables exposing pprof profiling endpoints. The profiling endpoints are exposed on the same port as the HTTP REST API under the /debug/pprof/ path. This can be useful for extension developers.
• #3442 adds a new --version flag, which has the same output as k6 version command. Thanks, @ffapitalle!
• #3423 adds an environment variable K6_INFLUXDB_PROXY to the InfluxDB output which allows specifying proxy. Thanks, @IvanovOleg!
• #3398 enables k6 cloud traces by default.
• #3400 sets a binary-based cloud output (a.k.a. cloud output v2) as the default version for streaming metrics from a local test run via -o cloud.
• #3452 adds fsext.Abs helper function.

Bug fixes

• #3380 corrects console.debug(), aligning -v output to --console-output and stdout.
• #3416 prints the stack trace when there's an exception in handleSummary().
• #3438 prevents an error on HTTP requests with content-encoding header and HTTP statuses known for having no body.
• browser#1077 fixes browserContext.clearPermissions to clear permissions without panic.
• browser#1042 fixes browserContext.waitForEvent which involved promisifying the waitForEvent API.
• browser#1078 fixes request interception deadlock to improve stability.
• browser#1101 fixes page.$ so that it returns null when no matches with given selector are found.
• #3397, #3427, #3417 update goja dependency. Fixes a possible panic and proper handling circular types at JSON.stringify. Fixes an issue about dumping the correct stack trace when an error is re-thrown.
• browser#1106 fixes an NPE on NavigateFrame when navigate occurs in the same document.
• browser#1096 fixes a panic when trying to interact within nested iframes. Thanks, @bandorko!

Maintenance and internal improvements

• #3378 fixes usage of gh in GitHub actions creating the OSS release.
• #3386, #3387, #3388, browser#1047 update dependencies.
• #3393, #3399 fix lint issues in the js package.
• #3381 disables temporarily ARM tests on GitHub Actions.
• #3401, #3469 refactors a Makefile, removes make ci-like-lint in favor of make lint. Updates a golangci-lint version to v1.55.2.
• #3410 fixes the tests reference in the all rule of the Makefile. Thanks, @flyck!
• #3402 adds a test-case for the k6 cloud.
• #3421 updates dependencies for xk6 integration tests.
• browser#1075, browser#1076 refactors clearPermissions and grantPermissions.
• browser#1043 refines tests.
• browser#1069, browser#1090 refactor internal.
• browser#1102 uses force and noWaitAfter in frame.newAction.
• #3443 mentions that k6-core team aims to support the last two major golang versions for building a k6 binary.
• #3437 switches k6 cloud traces to a new hostname.
• #3429 increases timeout expectations for the TestSetupTimeout test.
• #3446 moves log tokenizer to lib/strvals package.

Roadmap

Graduating from experimental

It has been a while since we've introduced the k6/experimental namespace. This namespace was specifically created to test new features before we fully committed to them. Thanks to it, we have been able to iterate on features and receive valuable feedback from the community before adding them to the core of k6.

In the following releases, we're going to graduate k6/experimental/grpc and k6/experimental/timers.

These modules' "experimental" versions will remain available for a couple of releases, but the goal is to remove the "experimental" imports for them in favor of the core-only imports.

New dashboard features

We're happy to announce our work on a new, upcoming dashboard feature. Based on the xk6-dashboard extension, this upcoming feature will enable you to visualize your test runs and their results in your web browser, in real time. The k6 maintainers team is starting to work towards its integration into the core of k6, and we're aiming to release it in the next couple of releases.

While the final user-experience might differ, you can already try it out by following the instructions in the xk6-dashboard repository. We update the extension on a regular basis as we're converging towards the first release of the feature in k6. Go ahead and give it a try! Let us know what you think about it!