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

mstoykov

I am not happy wiht making eventloop and errext depend on internal/log and given the naming errWithFieldsError likely should just be under errext but it might also be better to be moved somewhere else.

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.

inancgumus temporarily deployed to azure-trusted-signing May 12, 2026 18:32 — with GitHub Actions Inactive

inancgumus temporarily deployed to azure-trusted-signing May 12, 2026 18:35 — with GitHub Actions Inactive

inancgumus force-pushed the browser-loki-source-prototype branch from 6f3c7e6 to f776b45 Compare May 12, 2026 18:38

inancgumus temporarily deployed to azure-trusted-signing May 12, 2026 18:44 — with GitHub Actions Inactive

inancgumus temporarily deployed to azure-trusted-signing May 12, 2026 18:46 — with GitHub Actions Inactive

inancgumus force-pushed the browser-loki-source-prototype branch from f776b45 to 3a49f1d Compare May 12, 2026 18:51

inancgumus temporarily deployed to azure-trusted-signing May 12, 2026 18:57 — with GitHub Actions Inactive

inancgumus temporarily deployed to azure-trusted-signing May 12, 2026 18:59 — with GitHub Actions Inactive

inancgumus force-pushed the browser-loki-source-prototype branch from 3a49f1d to 2add0fb Compare May 12, 2026 19:23

inancgumus temporarily deployed to azure-trusted-signing May 12, 2026 19:29 — with GitHub Actions Inactive

inancgumus temporarily deployed to azure-trusted-signing May 12, 2026 19:36 — with GitHub Actions Inactive

inancgumus force-pushed the browser-loki-source-prototype branch from 2add0fb to c803029 Compare May 12, 2026 20:18

inancgumus temporarily deployed to azure-trusted-signing May 12, 2026 20:24 — with GitHub Actions Inactive

inancgumus temporarily deployed to azure-trusted-signing May 12, 2026 20:26 — with GitHub Actions Inactive

inancgumus force-pushed the browser-loki-source-prototype branch from c803029 to c527534 Compare May 12, 2026 20:26

inancgumus temporarily deployed to azure-trusted-signing May 12, 2026 20:32 — with GitHub Actions Inactive

inancgumus temporarily deployed to azure-trusted-signing May 12, 2026 20:34 — with GitHub Actions Inactive

inancgumus force-pushed the browser-loki-source-prototype branch from c527534 to f7fbade Compare May 12, 2026 21:10

inancgumus temporarily deployed to azure-trusted-signing May 12, 2026 21:16 — with GitHub Actions Inactive

inancgumus temporarily deployed to azure-trusted-signing May 12, 2026 21:18 — with GitHub Actions Inactive

inancgumus temporarily deployed to azure-trusted-signing May 12, 2026 22:01 — with GitHub Actions Inactive

inancgumus temporarily deployed to azure-trusted-signing May 12, 2026 22:03 — with GitHub Actions Inactive

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

inancgumus requested a review from a team as a code owner May 13, 2026 13:18

inancgumus requested review from mstoykov and szkiba and removed request for a team May 13, 2026 13:18

inancgumus self-assigned this May 13, 2026

inancgumus added the area: browser label May 13, 2026

szkiba previously approved these changes May 13, 2026

View reviewed changes

mstoykov previously requested changes May 15, 2026

View reviewed changes

Comment thread errext/format.go Outdated

Comment thread internal/js/eventloop/eventloop.go Outdated

Comment thread internal/log/error_fields.go Outdated

Comment thread internal/log/error_fields.go Outdated

mstoykov added this to the v2.1.0 milestone May 15, 2026

inancgumus dismissed szkiba’s stale review via 598be1a May 18, 2026 20:15

inancgumus force-pushed the browser-loki-source-prototype branch 2 times, most recently from 598be1a to 9657bd7 Compare May 18, 2026 20:16

inancgumus requested a review from mstoykov May 18, 2026 20:17

inancgumus temporarily deployed to azure-trusted-signing May 18, 2026 20:22 — with GitHub Actions Inactive

inancgumus temporarily deployed to azure-trusted-signing May 18, 2026 20:25 — with GitHub Actions Inactive

inancgumus force-pushed the browser-loki-source-prototype branch from 9657bd7 to 0c054cd Compare May 18, 2026 21:08

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

inancgumus temporarily deployed to azure-trusted-signing May 18, 2026 21:14 — with GitHub Actions Inactive

inancgumus temporarily deployed to azure-trusted-signing May 18, 2026 21:16 — with GitHub Actions Inactive

inancgumus force-pushed the browser-loki-source-prototype branch from 0c054cd to a327e4f Compare May 18, 2026 21:22

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.

inancgumus force-pushed the browser-loki-source-prototype branch from a327e4f to 6319394 Compare May 18, 2026 21:24

inancgumus temporarily deployed to azure-trusted-signing May 18, 2026 21:30 — with GitHub Actions Inactive

inancgumus temporarily deployed to azure-trusted-signing May 18, 2026 21:32 — with GitHub Actions Inactive

szkiba self-requested a review May 19, 2026 07:04

andrewslotin requested review from andrewslotin and removed request for mstoykov June 3, 2026 17:02

andrewslotin approved these changes Jun 3, 2026

View reviewed changes

szkiba approved these changes Jun 3, 2026

View reviewed changes

inancgumus merged commit 575e726 into master Jun 3, 2026
49 of 52 checks passed

inancgumus deleted the browser-loki-source-prototype branch June 3, 2026 18:08

BrewTestBot mentioned this pull request Jun 30, 2026

k6 2.1.0 Homebrew/homebrew-core#290548

Merged

Navigation Menu

Uh oh!

Preserve module source on API errors - #5971

Preserve module source on API errors#5971
inancgumus merged 4 commits into
masterfrom
browser-loki-source-prototype

inancgumus commented May 12, 2026 •

edited

Loading

Uh oh!

mstoykov left a comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

inancgumus commented May 18, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

Uh oh!

Conversation

inancgumus commented May 12, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

What?

Why?

Note

Related PR(s)/Issue(s)

Uh oh!

mstoykov left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

inancgumus commented May 18, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

inancgumus commented May 12, 2026 •

edited

Loading