Preserve module source on API errors by inancgumus · Pull Request #5971 · grafana/k6

inancgumus · 2026-05-12T18:26:19Z

What?

Browser API failures now log the browser module as module=browser.

This solution makes it ready to use even after we switch to slog for logging.
Browser failures that surface as iteration errors can be filtered as browser logs.
We don't override source as it's being used by other things, like stacktrace, console, http-debug, grafana-k6-cloud, etc. Some systems are parsing those, and we should not change them like so. So, we use module.

Why?

Users should be able to filter Cloud Logs for failures separately. A browser operation that failed during a test has already reached Cloud Logs, but it arrived without a label, so the source could not classify it as a browser op.

Note

Failing CI runs are not related to this PR.

Related PR(s)/Issue(s)

Related to grafana/k6-cloud#1318
Related to Reduce logging noise produced by the browser module as a default grafana-cold-storage/xk6-browser#1553

inancgumus · 2026-05-18T20:18:07Z

@mstoykov Please take another look. I've simplified the code.

Some errors need to carry extra log fields (like module origin) through the error chain. WithFields/FieldsFromErr attaches a map[string]any to any error. Format() merges these fields alongside hint into the returned fields map.

Unhandled promise rejections were formatted with fmt.Errorf, which stringified the rejection value and destroyed the original Go error chain. rejectionError keeps the cause accessible via Unwrap so errors.As can traverse the chain.

Iteration errors now carry their attached fields to the logger. Format() extracts any fields from the error chain, exceptions still get source=stacktrace. This removes the need for per-field checks in the executor.

Async rejects (promise helper) and sync throws (Panicf) now attach module=browser via WithFields. This lets Cloud Logs filter browser-originated errors without overriding the existing source field used by other systems.

The code has been updated per the feedback.

@nightt5879

k6 2.1.0 Created-by: HarmonybrewBot Commit-by: HarmonybrewBot Merged-by: HarmonybrewBot Description: Created by `brew bump` --- Created with `brew bump-formula-pr`.<details> <summary>release notes</summary> <pre>k6 `v2.1.0` is here 🎉 This release includes: - An opt-in feature-flag system — `--features`, the `K6_FEATURES` environment variable, and a `k6 features` discovery command — shipping with experimental native histograms for trend metrics as its first flag. - A context-level `proxy` option for browser contexts. - Subcommand discovery in `k6 x`, so binaries can report which extension commands they expose. ## Breaking changes There are no breaking changes in this release. ## New features ### `k6 cloud test list` command [#6007](grafana/k6#6007) A new `k6 cloud test` command group has been added, with a `k6 cloud test list` subcommand that lists the load tests of a Grafana Cloud k6 project. It complements the `k6 cloud project list` command introduced in v2.0.0. The project to list tests for is resolved in the following order: 1. The `--project-id` flag. 2. The `K6_CLOUD_PROJECT_ID` environment variable (cloud config `projectID`). 3. The default project of the configured stack, populated by `k6 cloud login`. Output defaults to a human-readable table. Pass `--json` to emit a JSON array instead, mirroring the format established by `k6 cloud project list`. ```shell k6 cloud test list k6 cloud test list --project-id 12345 k6 cloud test list --json ``` ### Feature flags and experimental native histograms [#6055](grafana/k6#6055), [#6056](grafana/k6#6056) k6 now has an opt-in feature-flag mechanism for trialing new, not-yet-stable behavior without affecting existing runs. Flags can be enabled on `k6 run` and `k6 cloud run` through the `--features` flag (comma-separated or repeated), the `K6_FEATURES` environment variable, or the `features` key in `config.json`. Enabled flags are surfaced as metric tags and propagated into archives and cloud workers so a run behaves consistently wherever it executes. Use `k6 features` (or `k6 features --json`) to discover the available flags and their lifecycle: ```console $ k6 features FEATURE LIFECYCLE DESCRIPTION native-histograms Experimental Use native histograms for trend metrics ``` The first flag shipped is `native-histograms`, an experimental flag that makes k6 use native histograms for trend metrics: ```shell k6 run --features native-histograms script.js # or K6_FEATURES=native-histograms k6 run script.js ``` ### Subcommand discovery in `k6 x` [#5972](grafana/k6#5972) Running `k6 x` now lists the available subcommands — both the ones baked into the binary and those advertised by the extension registry (official and community). Tab-completion surfaces the same set once the catalog has been cached locally by a prior `k6 x` run, so completion never blocks on the network. ```text $ k6 x ... Available Commands: agent Bootstrap an AI-assisted k6 testing workflow in any editor docs CLI k6 docs for AI agents and users explore Explore k6 extensions for Automatic Resolution mcp An MCP server for k6 for AI agents ``` This makes a k6 binary self-describing — particularly useful for AI agents driving k6, which previously had no way to introspect which extension subcommands were available. ### Browser context proxy option [#5924](grafana/k6#5924) Browser contexts can now be configured with a context-level `proxy` option, letting you route a context's traffic through a proxy without launching a custom-built binary or relying on environment proxy variables (which only affected k6's DevTools WebSocket connection). The option is wired to Chromium through `Target.createBrowserContext`, and invalid proxy configuration now fails early when `proxy.server` is missing. Thanks, @nightt5879! ```js const context = await browser.newContext({ proxy: { server: 'http://proxy.test:8080', bypass: 'localhost,127.0.0.1', }, }); ``` ### Browser `locator.isInViewport()` [#6023](grafana/k6#6023) A new `locator.isInViewport()` method reports whether an element intersects the browser viewport. It accepts an optional `ratio` (0 to 1) that sets how much of the element must be visible, defaulting to `0` so any visible pixel counts, matching Playwright's `toBeInViewport` semantics. The call waits for the element to attach, honoring the `timeout` option, then measures the intersection once. Thanks, @Anuragp22! ```js const button = page.locator('button#submit'); if (await button.isInViewport()) { await button.click(); } ``` ### Basic auth for the OpenTelemetry HTTP exporter [#5997](grafana/k6#5997) The OpenTelemetry output's HTTP exporter can now send HTTP Basic Auth credentials. Set them through the `K6_OTEL_HTTP_EXPORTER_USERNAME` and `K6_OTEL_HTTP_EXPORTER_PASSWORD` environment variables, or the `username` and `password` keys in the output config. ```shell K6_OTEL_HTTP_EXPORTER_USERNAME=user \ K6_OTEL_HTTP_EXPORTER_PASSWORD=secret \ k6 run --out opentelemetry script.js ``` ### `single()` selection helper in `k6/html` [#6002](grafana/k6#6002) `Selection.single(selector)` returns at most one matching element, backed by goquery's `Single` matcher for a faster lookup than `find()` when you only need the first match. Thanks, @rohan-patnaik! ```js import { parseHTML } from 'k6/html'; const doc = parseHTML(content); const title = doc.single('h1').text(); ``` ## UX improvements and enhancements - [#5971](grafana/k6#5971) Tags browser API failures with `module=browser` so that browser errors surfaced in Grafana Cloud Logs can be filtered separately from other log sources. ## Bug fixes - [#5794](grafana/k6#5794) Makes the `--vus` flag work as a standalone execution shortcut instead of being silently ignored when a script defines scenarios. Running `k6 run script.js --vus N` now creates a `shared-iterations` scenario with `N` VUs and `N` iterations, overriding any script-defined scenarios with a warning — consistent with how `--iterations`, `--duration`, and `--stages` already behave. Thanks, @Reranko05! - [#6013](grafana/k6#6013) Rejects invalid threshold percentiles. A percentile aggregation value outside the 0 to 100 range (or `NaN`) now fails parsing with a clear message instead of being silently accepted. Thanks, @immanuwell! - [#6011](grafana/k6#6011) Writes the on-disk k6 config file with owner-only permissions (`0o600`, inside a `0o700` directory). The file can hold the Grafana Cloud API token (`collectors.cloud.token`), so tightening it keeps other local users on shared hosts (CI runners, multi-user boxes, sidecar containers) from reading the token. Existing configs are upgraded on the next write, for example the next `k6 cloud login`. ## Maintenance and internal improvements - [#6033](grafana/k6#6033) Moves Docker Hub image publishing to a Google Artifact Registry mirror. - [#5953](grafana/k6#5953) Installs `s3cmd` via `apt` instead of `pip` to fix the `k6packager` image build. - [#6052](grafana/k6#6052) Fixes the browser end-to-end test workflow. - [#5984](grafana/k6#5984) Routes per-test logger output to the test instance instead of the global `logrus`, improving test isolation. - [#5985](grafana/k6#5985) Fixes the flaky `TestPageScreenshotFullpage` browser test. - [#5981](grafana/k6#5981) Lets Renovate track the Go minor version in the `setup-go` workflows. - [#5968](grafana/k6#5968) Honors the caller-pinned ref in the shared lint action. - [#6041](grafana/k6#6041), [#6054](grafana/k6#6054) Aligns the Go module directive and toolchain (1.25.0 / 1.25.11). - [#5967](grafana/k6#5967) Updates the release notes template after v2.0.0. - [#6015](grafana/k6#6015) Updates `golang.org/x/net` to `v0.55.0` [security]. - [#6026](grafana/k6#6026) Updates `golang.org/x/crypto` to `v0.52.0` [security]. - [#5962](grafana/k6#5962), [#6028](grafana/k6#6028) Updates `google.golang.org/grpc` to `v1.81.1`. - [#5960](grafana/k6#5960) Updates `grafana/shared-workflows/get-vault-secrets` to `v1.3.2`. - [#5958](grafana/k6#5958) Updates `grafana/shared-workflows/azure-trusted-signing` to `v1.0.2`. - [#5957](grafana/k6#5957) Updates `github/codeql-action` to `v4.35.4`. - [#5959](grafana/k6#5959) Updates `grafana/shared-workflows/dockerhub-login` to `v1.0.4`. - [#6009](grafana/k6#6009) Moves the browser `PageScreenshotOptions` parsing into the mapping layer. - [#5964](grafana/k6#5964) Adds the k6 feature-flags specification under `openspec/`. - [#6067](grafana/k6#6067) Forces the legacy `x/net/http2` implementation on the `gotip` CI test job. - [#6065](grafana/k6#6065) Lets Renovate update the `Dockerfile` on the v1.x branch. - [#6031](grafana/k6#6031) Updates `go.opentelemetry.io/otel` to `v1.44.0`. - [#6086](grafana/k6#6086) Updates `golang.org/x` dependencies (`crypto` to `v0.53.0`, `net` to `v0.56.0`, `term` to `v0.44.0`). - [#6061](grafana/k6#6061) Updates `golang.org/x/sync` to `v0.21.0`. - [#6030](grafana/k6#6030) Updates `github.com/tidwall/gjson` to `v1.19.0`. - [#6029](https: See merge request: Harmonybrew/homebrew-core!13169

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inancgumus marked this pull request as ready for review May 13, 2026 13:18

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inancgumus changed the title ~~browser: preserve source on API errors~~ Preserve module source on API errors May 18, 2026

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inancgumus added 4 commits May 18, 2026 17:24

errext: add WithFields for structured error metadata

c2ac15c

Some errors need to carry extra log fields (like module origin) through the error chain. WithFields/FieldsFromErr attaches a map[string]any to any error. Format() merges these fields alongside hint into the returned fields map.

eventloop: preserve Go error chain on rejections

cce7f5a

Unhandled promise rejections were formatted with fmt.Errorf, which stringified the rejection value and destroyed the original Go error chain. rejectionError keeps the cause accessible via Unwrap so errors.As can traverse the chain.

executor: log fields from error metadata

0475c96

Iteration errors now carry their attached fields to the logger. Format() extracts any fields from the error chain, exceptions still get source=stacktrace. This removes the need for per-field checks in the executor.

browser: tag API errors with module "browser"

6319394

Async rejects (promise helper) and sync throws (Panicf) now attach module=browser via WithFields. This lets Cloud Logs filter browser-originated errors without overriding the existing source field used by other systems.

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inancgumus merged commit 575e726 into master Jun 3, 2026
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k6 2.1.0 Homebrew/homebrew-core#290548

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Preserve module source on API errors - #5971

Preserve module source on API errors#5971
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