test(ci): raise Windows vitest worker cap from 2 to 4 by killagu · Pull Request #6005 · eggjs/egg

killagu · 2026-06-27T14:04:35Z

Motivation

The Windows CI override in vitest.config.ts pinned the vitest threads pool to maxWorkers: 2 (added in #5926 for stability). The standard GitHub windows-latest runner has 4 vCPUs, so this left half the runner idle and made Windows the slowest matrix leg.

Scope

Single-line config change: raise the Windows-CI maxWorkers cap from 2 to 4, with a comment documenting the rationale. No change to posix (linux/macOS) behavior.

+    // Windows CI is more contention-sensitive than posix, so we cap the thread
+    // pool. Use the full standard `windows-latest` runner (4 vCPU) instead of the
+    // previous hard cap of 2; the suite already retries flaky tests (--retry 2).
     ...(isWindowsCI
       ? {
-          maxWorkers: 2,
+          maxWorkers: 4,
         }
       : {}),

Stability

The original cap was conservative; stability is preserved by the existing retry safety net — the root test script runs vitest run --bail 1 --retry 2 ..., so transient contention flakes are retried (up to 2×) before failing the run. The Windows test matrix (windows-latest × Node 22/24) plus test-egg-bin Windows leg in this CI run are the real validation. If higher contention proves flaky, the fallback is maxWorkers: 3.

Test evidence

oxfmt --check vitest.config.ts passes.
Windows stability can only be validated on the runner itself — this is verified by the Test (windows-latest, 22/24) and Test bin (windows-latest, 24) CI legs on this PR.

🤖 Generated with Claude Code

Summary by CodeRabbit

Bug Fixes
- Improved test stability on Windows CI by increasing the maximum parallel test workers (from 2 to 4), which may reduce flaky failures and speed up validation.

The Windows CI override pinned the vitest threads pool to `maxWorkers: 2`, leaving half of the 4-vCPU `windows-latest` runner idle. Raise the cap to 4 to fully use the runner and roughly halve Windows test wall-clock. Stability is preserved by the existing retry safety net: the root `test` script runs with `--retry 2`, so transient contention flakes are retried before failing the run. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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coderabbitai · 2026-06-27T14:04:50Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 80683bb4-99ab-4e15-9de6-7bafa119f1f9

📥 Commits

Reviewing files that changed from the base of the PR and between 36d8650 and ec598c8.

📒 Files selected for processing (1)

vitest.config.ts

🚧 Files skipped from review as they are similar to previous changes (1)

vitest.config.ts

📝 Walkthrough

Walkthrough

The Vitest configuration's Windows CI concurrency cap (maxWorkers) is increased from 2 to 4, with new inline comments explaining that this uses the full windows-latest runner capacity and relies on --retry 2 for flaky tests.

Windows CI Vitest Config

Layer / File(s)	Summary
Windows CI maxWorkers update `vitest.config.ts`	`maxWorkers` under the `isWindowsCI` condition raised from `2` to `4`; added comments on contention handling and flaky test retry strategy.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Poem

A rabbit hops through CI lanes,
Four workers now share Windows pains,
No more two-worker crawl so slow,
With retries set, we let it flow,
🐇 More cores, more speed, let tests go! 🚀

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main Windows CI Vitest worker cap increase from 2 to 4.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

Create stacked PR
Commit on current branch

🧪 Generate unit tests (beta)

Create PR with unit tests
Commit unit tests in branch feat/windows-ci-concurrency

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gemini-code-assist

Code Review

This pull request increases the maxWorkers limit from 2 to 4 for Windows CI in vitest.config.ts. The reviewer points out that standard GitHub-hosted Windows runners only have 2 vCPUs, so setting maxWorkers to 4 may cause CPU contention and increase test flakiness. They suggest reverting the limit back to 2.

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gemini-code-assist · 2026-06-27T14:05:21Z

+    // Windows CI is more contention-sensitive than posix, so we cap the thread
+    // pool. Use the full standard `windows-latest` runner (4 vCPU) instead of the
+    // previous hard cap of 2; the suite already retries flaky tests (--retry 2).
    ...(isWindowsCI
      ? {
-          maxWorkers: 2,
+          maxWorkers: 4,
        }
      : {}),


The standard GitHub-hosted windows-latest runner actually has 2 vCPUs (2 cores), not 4 vCPUs. Setting maxWorkers: 4 on a 2-core machine will cause over-provisioning, leading to CPU contention and thread thrashing. Since Windows is particularly sensitive to process/thread context switching and file I/O overhead, this can significantly increase test flakiness and potentially slow down the overall test execution rather than speeding it up. It is highly recommended to keep maxWorkers: 2 to match the actual hardware resources of the standard runner.

Suggested change

// Windows CI is more contention-sensitive than posix, so we cap the thread

// pool. Use the full standard `windows-latest` runner (4 vCPU) instead of the

// previous hard cap of 2; the suite already retries flaky tests (--retry 2).

...(isWindowsCI

? {

maxWorkers: 2,

maxWorkers: 4,

}

: {}),

// Windows CI is more contention-sensitive than posix, so we cap the thread

// pool. Use the standard windows-latest runner's 2 vCPUs to avoid

// excessive resource contention.

...(isWindowsCI

? {

maxWorkers: 2,

}

: {}),

This is based on an outdated spec. GitHub doubled the public-repository standard runners (Linux + Windows) to 4 vCPU / 16 GiB in early 2024:

Any Linux or Windows workflow triggered from a public repository, using GitHub's default labels, will run on 4-vCPU runners.

windows-latest standard Public repo Private repo

vCPU / RAM 4 / 16 GB 2 / 8 GB

The "2 vCPU" figure is the private-repo tier. eggjs/egg is a public repository, so its windows-latest legs run on the 4-vCPU runner — maxWorkers: 4 matches the hardware 1:1, it is not over-provisioning. The previous maxWorkers: 2 was leaving half the runner idle.

The general point about Windows being context-switch/IO-sensitive is fair, but it was derived from the wrong core count. As a safeguard the suite already runs with --retry 2, and the Windows CI legs on this PR are the empirical check; if they flake at 4 workers the fallback is maxWorkers: 3 (one core of headroom).

Refs:

https://docs.github.com/en/actions/reference/runners/github-hosted-runners

https://github.blog/news-insights/product-news/github-hosted-runners-double-the-power-for-open-source/

cloudflare-workers-and-pages · 2026-06-27T14:07:42Z

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cloudflare-workers-and-pages · 2026-06-27T14:09:11Z

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…rrency # Conflicts: # vitest.config.ts

codecov · 2026-06-27T14:44:43Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.91%. Comparing base (f9662dc) to head (ec598c8).
⚠️ Report is 1 commits behind head on next.

Additional details and impacted files

@@            Coverage Diff             @@
##             next    #6005      +/-   ##
==========================================
- Coverage   84.92%   84.91%   -0.01%     
==========================================
  Files         676      676              
  Lines       20513    20513              
  Branches     4058     4058              
==========================================
- Hits        17421    17419       -2     
- Misses       2663     2665       +2     
  Partials      429      429

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Copilot AI review requested due to automatic review settings June 27, 2026 14:04

Copilot AI reviewed Jun 27, 2026

gemini-code-assist Bot reviewed Jun 27, 2026

View reviewed changes

Merge remote-tracking branch 'origin/next' into feat/windows-ci-concu…

ec598c8

…rrency # Conflicts: # vitest.config.ts

killagu merged commit 4fa509e into next Jun 27, 2026
22 of 25 checks passed

killagu deleted the feat/windows-ci-concurrency branch June 27, 2026 14:50

coderabbitai Bot mentioned this pull request Jun 27, 2026

perf(egg-bin): boot TypeScript via @oxc-node/core instead of ts-node #6007

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test(ci): raise Windows vitest worker cap from 2 to 4#6005

test(ci): raise Windows vitest worker cap from 2 to 4#6005
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