[turbopack] Don't schedule idle snapshots when we are in a short session by lukesandberg · Pull Request #90804 · vercel/next.js

lukesandberg · 2026-03-03T06:57:31Z

In a few next build commands i saw multiple snapshots due to this. Idle callbacks were firing near the end of the build.

  Creating an optimized production build ...
WARNING: The git repository is dirty, but File System Cache is still enabled. Manual removal of the filesystem cache database might be required.
✓ Finished writing to filesystem cache because: idle timeout in 6.1s
✓ Compiled successfully in 69s
✓ Collecting page data using 13 workers in 85ms
  Build ran with "compile" mode, to finalize the build run either "generate" or "generate-env" mode as well
✓ Finalizing page optimization in 32ms
Route (app)
...ommitted route table...
✓ Finished writing to filesystem cache because: stop in 3.5s

This is a bit wasteful since it is more efficient to write everything in a single batch at the end.

The solution is just to not schedule snapshotting operations in 'short sessions' (aka next build)

lukesandberg · 2026-03-03T06:57:48Z

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nextjs-bot · 2026-03-03T07:12:25Z

Tests Passed

codspeed-hq · 2026-03-03T07:18:48Z

Merging this PR will not alter performance

✅ 17 untouched benchmarks
⏩ 3 skipped benchmarks¹

_{Comparing lukesandberg/idle_callbacks_in_build_are_suspicious (fec6d53) with canary (5102fd0)}

3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

nextjs-bot · 2026-03-03T07:20:53Z

Stats from current PR

✅ No significant changes detected

📊 All Metrics

📖 Metrics Glossary

Dev Server Metrics:

Listen = TCP port starts accepting connections
First Request = HTTP server returns successful response
Cold = Fresh build (no cache)
Warm = With cached build artifacts

Build Metrics:

Fresh = Clean build (no .next directory)
Cached = With existing .next directory

Change Thresholds:

Time: Changes < 50ms AND < 10%, OR < 2% are insignificant
Size: Changes < 1KB AND < 1% are insignificant
All other changes are flagged to catch regressions

⚡ Dev Server

Metric	Canary	PR	Change	Trend
Cold (Listen)	455ms	455ms	✓	▁▁▁▁▁
Cold (Ready in log)	438ms	439ms	✓	▁▁▁▁▁
Cold (First Request)	1.243s	1.261s	✓	▁▂▁▁▂
Warm (Listen)	457ms	456ms	✓	▁▁▁▁▁
Warm (Ready in log)	443ms	443ms	✓	▁▁▁▁▁
Warm (First Request)	351ms	348ms	✓	▁▁▁▁▁

📦 Dev Server (Webpack) (Legacy)

📦 Dev Server (Webpack)

Metric	Canary	PR	Change	Trend
Cold (Listen)	506ms	507ms	✓	▁▁▁█▁
Cold (Ready in log)	473ms	474ms	✓	▄▄▁▆▃
Cold (First Request)	2.156s	2.155s	✓	▂▃▁▇▂
Warm (Listen)	508ms	508ms	✓	▁▁▁█▁
Warm (Ready in log)	471ms	470ms	✓	▅▄▁▇▄
Warm (First Request)	2.148s	2.147s	✓	▃▃▁▆▂

⚡ Production Builds

Metric	Canary	PR	Change	Trend
Fresh Build	3.942s	3.934s	✓	▁▁▁▁▁
Cached Build	3.915s	3.891s	✓	▁▁▁▁▁

📦 Production Builds (Webpack) (Legacy)

📦 Production Builds (Webpack)

Metric	Canary	PR	Change	Trend
Fresh Build	15.771s	15.800s	✓	▁▃▁▆▁
Cached Build	15.869s	15.834s	✓	▁▃▁▆▁
node_modules Size	476 MB	476 MB	✓	▁▁▁▁▁

📦 Bundle Sizes

Bundle Sizes

⚡ Turbopack

Client

Main Bundles: **401 kB** → **401 kB** ✅ -23 B

80 files with content-based hashes (individual files not comparable between builds)

Server

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	768 B	765 B	✓
Total	768 B	765 B	✅ -3 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	450 B	450 B	✓
Total	450 B	450 B	✓

📦 Webpack

Client

Main Bundles

	Canary	PR	Change
5528-HASH.js gzip	5.54 kB	N/A	-
6280-HASH.js gzip	58.7 kB	N/A	-
6335.HASH.js gzip	169 B	N/A	-
912-HASH.js gzip	4.59 kB	N/A	-
e8aec2e4-HASH.js gzip	62.6 kB	N/A	-
framework-HASH.js gzip	59.7 kB	59.7 kB	✓
main-app-HASH.js gzip	256 B	254 B	✓
main-HASH.js gzip	39.1 kB	39.1 kB	✓
webpack-HASH.js gzip	1.68 kB	1.68 kB	✓
262-HASH.js gzip	N/A	4.59 kB	-
2889.HASH.js gzip	N/A	169 B	-
5602-HASH.js gzip	N/A	5.55 kB	-
6948ada0-HASH.js gzip	N/A	62.6 kB	-
9544-HASH.js gzip	N/A	59.4 kB	-
Total	232 kB	233 kB	⚠️ +731 B

Polyfills

	Canary	PR	Change
polyfills-HASH.js gzip	39.4 kB	39.4 kB	✓
Total	39.4 kB	39.4 kB	✓

Pages

	Canary	PR	Change
_app-HASH.js gzip	194 B	194 B	✓
_error-HASH.js gzip	183 B	180 B	🟢 3 B (-2%)
css-HASH.js gzip	331 B	330 B	✓
dynamic-HASH.js gzip	1.81 kB	1.81 kB	✓
edge-ssr-HASH.js gzip	256 B	256 B	✓
head-HASH.js gzip	351 B	352 B	✓
hooks-HASH.js gzip	384 B	383 B	✓
image-HASH.js gzip	580 B	581 B	✓
index-HASH.js gzip	260 B	260 B	✓
link-HASH.js gzip	2.5 kB	2.5 kB	✓
routerDirect..HASH.js gzip	320 B	319 B	✓
script-HASH.js gzip	386 B	386 B	✓
withRouter-HASH.js gzip	315 B	315 B	✓
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Total	7.97 kB	7.97 kB	✅ -2 B

Server

Edge SSR

	Canary	PR	Change
edge-ssr.js gzip	125 kB	125 kB	✓
page.js gzip	255 kB	255 kB	✓
Total	380 kB	380 kB	⚠️ +268 B

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	618 B	613 B	✓
middleware-r..fest.js gzip	156 B	155 B	✓
middleware.js gzip	43.6 kB	43.7 kB	✓
edge-runtime..pack.js gzip	842 B	842 B	✓
Total	45.2 kB	45.3 kB	⚠️ +105 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	715 B	718 B	✓
Total	715 B	718 B	⚠️ +3 B

Build Cache

	Canary	PR	Change
0.pack gzip	4.05 MB	4.06 MB	🔴 +12 kB (+0%)
index.pack gzip	104 kB	103 kB	✓
index.pack.old gzip	103 kB	103 kB	✓
Total	4.26 MB	4.27 MB	⚠️ +10.7 kB

🔄 Shared (bundler-independent)

Runtimes

	Canary	PR	Change
app-page-exp...dev.js gzip	321 kB	321 kB	✓
app-page-exp..prod.js gzip	170 kB	170 kB	✓
app-page-tur...dev.js gzip	320 kB	320 kB	✓
app-page-tur..prod.js gzip	170 kB	170 kB	✓
app-page-tur...dev.js gzip	317 kB	317 kB	✓
app-page-tur..prod.js gzip	168 kB	168 kB	✓
app-page.run...dev.js gzip	317 kB	317 kB	✓
app-page.run..prod.js gzip	168 kB	168 kB	✓
app-route-ex...dev.js gzip	70.8 kB	70.8 kB	✓
app-route-ex..prod.js gzip	49.3 kB	49.3 kB	✓
app-route-tu...dev.js gzip	70.9 kB	70.9 kB	✓
app-route-tu..prod.js gzip	49.3 kB	49.3 kB	✓
app-route-tu...dev.js gzip	70.5 kB	70.5 kB	✓
app-route-tu..prod.js gzip	49 kB	49 kB	✓
app-route.ru...dev.js gzip	70.4 kB	70.4 kB	✓
app-route.ru..prod.js gzip	49 kB	49 kB	✓
dist_client_...dev.js gzip	324 B	324 B	✓
dist_client_...dev.js gzip	326 B	326 B	✓
dist_client_...dev.js gzip	318 B	318 B	✓
dist_client_...dev.js gzip	317 B	317 B	✓
pages-api-tu...dev.js gzip	43.2 kB	43.2 kB	✓
pages-api-tu..prod.js gzip	32.9 kB	32.9 kB	✓
pages-api.ru...dev.js gzip	43.2 kB	43.2 kB	✓
pages-api.ru..prod.js gzip	32.9 kB	32.9 kB	✓
pages-turbo....dev.js gzip	52.6 kB	52.6 kB	✓
pages-turbo...prod.js gzip	38.5 kB	38.5 kB	✓
pages.runtim...dev.js gzip	52.6 kB	52.6 kB	✓
pages.runtim..prod.js gzip	38.5 kB	38.5 kB	✓
server.runti..prod.js gzip	62 kB	62 kB	✓
Total	2.83 MB	2.83 MB	✅ -4 B

📎 Tarball URL

https://vercel-packages.vercel.app/next/commits/bb1c8f29b9e5b68f60446e833088083cccfc3d8d/next

lukesandberg · 2026-03-03T07:58:54Z

Merge activity

Mar 3, 7:58 AM UTC: @lukesandberg merged this pull request with Graphite.

don't schedule idle snapshots when we are in a short session

fec6d53

nextjs-bot added created-by: Turbopack team PRs by the Turbopack team. Turbopack Related to Turbopack with Next.js. labels Mar 3, 2026

This was referenced Mar 3, 2026

[turbopack] Encode task storage directly during persistence (skip clone) #89412

Open

[turbopack] Move empty snapshot filtering into take_snapshot #90166

Open

lukesandberg mentioned this pull request Mar 3, 2026

[turbopack] Share scratch buffer across shards using thread local #90167

Draft

lukesandberg changed the title ~~don't schedule idle snapshots when we are in a short session~~ [turbopack] Don't schedule idle snapshots when we are in a short session Mar 3, 2026

lukesandberg marked this pull request as ready for review March 3, 2026 07:21

lukesandberg requested a review from sokra March 3, 2026 07:21

sokra approved these changes Mar 3, 2026

View reviewed changes

lukesandberg merged commit 8b70c61 into canary Mar 3, 2026
292 of 298 checks passed

lukesandberg deleted the lukesandberg/idle_callbacks_in_build_are_suspicious branch March 3, 2026 07:58

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[turbopack] Don't schedule idle snapshots when we are in a short session#90804

[turbopack] Don't schedule idle snapshots when we are in a short session#90804
lukesandberg merged 1 commit intocanaryfrom
lukesandberg/idle_callbacks_in_build_are_suspicious

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Merging this PR will not alter performance

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Stats from current PR

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