Remove limit on max parallel file ops by lukastaegert · Pull Request #5986 · rollup/rollup

lukastaegert · 2025-06-15T05:08:01Z

This PR contains:

Are tests included?

yes (bugfixes and features will not be merged without tests)
no

Breaking Changes?

yes (breaking changes will not be merged unless absolutely necessary)
no

List any relevant issue numbers:

resolves The build does not fail and stalls if the load hook is called concurrently more than maxParallelFileOps in watch mode #5848

Description

If we hit this limit for this.load calls, it leads to a very unpleasant "hanging" situation for users.

vercel · 2025-06-15T05:08:05Z

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github-actions · 2025-06-15T05:14:37Z

Thank you for your contribution! ❤️

You can try out this pull request locally by installing Rollup via

npm install rollup/rollup#gh-5848_remove_file_ops_limit

Notice: Ensure you have installed the latest stable Rust toolchain. If you haven't installed it yet, please see https://www.rust-lang.org/tools/install to learn how to download Rustup and install Rust.

or load it into the REPL:
https://rollup-dc32alhjk-rollup-js.vercel.app/repl/?pr=5986

github-actions · 2025-06-15T05:16:23Z

Performance report

BUILD: 6915ms (-275ms, -3.8%), 830 MB (+9%)
- initialize: 0ms, 24.6 MB
- generate module graph: 2548ms (-174ms, -6.4%), 629 MB (+10%)
  - generate ast: 1390ms (+181ms, +15.0%), 623 MB (+11%)
- sort and bind modules: 393ms (-30ms, -7.2%), 680 MB (+11%)
- mark included statements: 3981ms, 830 MB (+9%)
  - treeshaking pass 1: 2319ms, 813 MB (+6%)
  - treeshaking pass 2: 469ms, 837 MB (+7%)
  - treeshaking pass 3: 404ms, 823 MB (+8%)
  - treeshaking pass 4: 393ms, 842 MB (+7%)
  - treeshaking pass 5: 391ms, 830 MB (+9%)
GENERATE: 892ms (+193ms, +27.7%), 927 MB (-8%)
- initialize render: 0ms, 842 MB (-5%)
- generate chunks: 145ms (+91ms, +169.6%), 838 MB (-7%)
  - optimize chunks: 0ms, 855 MB (-4%)
- render chunks: 649ms (+26ms, +4.2%), 901 MB (-7%)
- transform chunks: 19ms, 927 MB (-8%)
- generate bundle: 0ms, 927 MB (-8%)

codecov · 2025-06-15T05:20:48Z

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.78%. Comparing base (5dcce11) to head (1556285).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5986      +/-   ##
==========================================
- Coverage   98.78%   98.78%   -0.01%     
==========================================
  Files         270      270              
  Lines        8735     8734       -1     
  Branches     1510     1510              
==========================================
- Hits         8629     8628       -1     
  Misses         73       73              
  Partials       33       33

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github-actions · 2025-06-19T06:23:55Z

This PR has been released as part of rollup@4.44.0. You can test it via npm install rollup.

rwv · 2025-06-23T13:03:46Z

Hi @lukastaegert,

I’m currently encountering an EMFILE: too many open files error during builds both on Windows and on macOS, which seems related to the file resolver. I noticed this PR removes the limit on max parallel file operations, so I suspect it might be connected.

Here’s an example error log (paths simplified):

error during build:
[commonjs--resolver] Could not load some.js: EMFILE: too many open files
    at async open (node:internal/fs/promises:639:25)
    at async Object.readFile (node:internal/fs/promises:1246:14)
    at async Object.handler (.../node_modules/vite/dist/node/chunks/dep-DBxKXgDP.js:45843:27)
    at async PluginDriver.hookFirstAndGetPlugin (.../node_modules/rollup/dist/es/shared/node-entry.js:22166:28)
    at async .../node_modules/rollup/dist/es/shared/node-entry.js:21170:33
    at async Queue.work (.../node_modules/rollup/dist/es/shared/node-entry.js:22394:32)

I’m still investigating on my side but wanted to share this in case it helps track related issues.

Thanks so much for your work on Rollup! 🙏

Package:
vite: 6.3.5
rollup: 4.44.0

rwv · 2025-06-23T13:31:46Z

I downgraded Rollup to 4.43.0 and the EMFILE issue is gone. I’ll open a new issue with more details shortly.

Stencil bundles Rollup 4.34.9, which contains a known deadlock bug (rollup/rollup#5848) that causes watch mode rebuilds to hang indefinitely at 'generate lazy + source maps'. The issue occurs because the `@rollup/plugin-commonjs` `load` hook calls `this.load()` internally. With Rollup's `maxParallelFileOps` defaulting to 20, the outer `load` calls saturate the file operation queue, and the nested `this.load()` calls queue behind them — creating a deadlock where no task can complete. This is triggered on rebuild because Rollup passes all cached modules (3000+ in a large project) through the load pipeline simultaneously. Rollup 4.44.0 fixes this by changing the default `maxParallelFileOps` to Infinity (rollup/rollup#5986). Closes stenciljs#6253

Stencil bundles Rollup 4.34.9, which contains a known deadlock bug (rollup/rollup#5848) that causes watch mode rebuilds to hang indefinitely at 'generate lazy + source maps'. The issue occurs because the `@rollup/plugin-commonjs` `load` hook calls `this.load()` internally. With Rollup's `maxParallelFileOps` defaulting to 20, the outer `load` calls saturate the file operation queue, and the nested `this.load()` calls queue behind them — creating a deadlock where no task can complete. This is triggered on rebuild because Rollup passes all cached modules (3000+ in a large project) through the load pipeline simultaneously. Rollup 4.44.0 fixes this by changing the default `maxParallelFileOps` to Infinity (rollup/rollup#5986). Closes stenciljs#6602

Stencil bundles Rollup 4.34.9, which contains a known deadlock bug (rollup/rollup#5848) that causes watch mode rebuilds to hang indefinitely at 'generate lazy + source maps'. The `@rollup/plugin-commonjs` `load` hook calls `this.load()` internally. With Rollup's `maxParallelFileOps` defaulting to 20, the outer load calls saturate the file operation queue, and the nested `this.load()` calls queue behind them — creating a deadlock. This is triggered on rebuild because Rollup passes all cached modules (3000+ in a large project) through the load pipeline simultaneously. Rollup 4.44.0 fixes this by changing the default `maxParallelFileOps` to Infinity (rollup/rollup#5986). fixes: stenciljs#6602

Stencil bundles Rollup 4.34.9, which contains a known deadlock bug (rollup/rollup#5848) that causes watch mode rebuilds to hang indefinitely at 'generate lazy + source maps'. The `@rollup/plugin-commonjs` `load` hook calls `this.load()` internally. With Rollup's `maxParallelFileOps` defaulting to 20, the outer load calls saturate the file operation queue, and the nested `this.load()` calls queue behind them — creating a deadlock. This is triggered on rebuild because Rollup passes all cached modules (3000+ in a large project) through the load pipeline simultaneously. Rollup 4.44.0 fixes this by changing the default `maxParallelFileOps` to Infinity (rollup/rollup#5986). fixes: #6602

Remove limit on max parallel file ops

0a296b9

lukastaegert force-pushed the gh-5848_remove_file_ops_limit branch from 5f807ea to 0a296b9 Compare June 15, 2025 05:09

vercel bot deployed to Preview June 15, 2025 05:11 View deployment

Merge branch 'master' into gh-5848_remove_file_ops_limit

1556285

lukastaegert enabled auto-merge June 19, 2025 04:59

vercel bot deployed to Preview June 19, 2025 05:01 View deployment

rollup-bot approved these changes Jun 19, 2025

View reviewed changes

lukastaegert added this pull request to the merge queue Jun 19, 2025

github-merge-queue bot removed this pull request from the merge queue due to failed status checks Jun 19, 2025

lukastaegert added this pull request to the merge queue Jun 19, 2025

Merged via the queue into master with commit 0b3e6bf Jun 19, 2025
42 checks passed

lukastaegert deleted the gh-5848_remove_file_ops_limit branch June 19, 2025 05:43

github-actions bot mentioned this pull request Jun 19, 2025

The build does not fail and stalls if the load hook is called concurrently more than maxParallelFileOps in watch mode #5848

Closed

rwv mentioned this pull request Jun 23, 2025

EMFILE: too many open files when upgrading to 4.44.0 #5989

Closed

silverwind mentioned this pull request Jun 24, 2025

--watch mode gets stuck on rebuild in v6 vitejs/vite#19410

Closed

7 tasks

adrianschmidt mentioned this pull request Feb 18, 2026

bug: watch rebuild hangs due to Rollup fileOperationQueue deadlock (bundled Rollup 4.34.9) stenciljs/core#6602

Closed

3 tasks

adrianschmidt mentioned this pull request Feb 18, 2026

fix(compiler): update rollup to fix watch hang stenciljs/core#6603

Merged

2 tasks

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Remove limit on max parallel file ops#5986

Remove limit on max parallel file ops#5986
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gh-5848_remove_file_ops_limit

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