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fix(cloudflare): avoid repeated flush lock wrapping - #21156

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awad/js-2605-makeflushlock-grows-a-waituntil-wrapper-chain-on-every-init
May 26, 2026
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fix(cloudflare): avoid repeated flush lock wrapping#21156
logaretm merged 3 commits into
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awad/js-2605-makeflushlock-grows-a-waituntil-wrapper-chain-on-every-init

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@logaretm

@logaretmlogaretm commented May 25, 2026•
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Durable Objects can reuse the same instrumented context across many requests. makeFlushLock() replaced context.waitUntil on every init, so each request wrapped the previous wrapper and built an unbounded call chain.

A later waitUntil() call then had to recurse through every wrapper, eventually causing stack overflows and retaining stale closures.

I added a mechanism to reuse a single waitUntil wrapper per Cloudflare context instead of wrapping again on every SDK init. Also added a regression coverage for long-lived contexts repeatedly creating flush locks.

Fixes#21150

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linear-codeBot commented May 25, 2026

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JS-2605

@logaretmlogaretm changed the title test(cloudflare): reproduce flush lock wrapper growthfix(cloudflare): avoid repeated flush lock wrappingMay 25, 2026
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logaretm marked this pull request as ready for review May 25, 2026 11:01
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logaretm requested a review from a team as a code ownerMay 25, 2026 11:01
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logaretm requested review from JPeer264 and andreiborza and removed request for a teamMay 25, 2026 11:01
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size-limit report 📦

PathSize% ChangeChange
@sentry/browser27.32 kB--
@sentry/browser - with treeshaking flags25.74 kB--
@sentry/browser (incl. Tracing)45.31 kB--
@sentry/browser (incl. Tracing + Span Streaming)47.55 kB--
@sentry/browser (incl. Tracing, Profiling)50.3 kB--
@sentry/browser (incl. Tracing, Replay)84.92 kB--
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags74.43 kB--
@sentry/browser (incl. Tracing, Replay with Canvas)89.64 kB--
@sentry/browser (incl. Tracing, Replay, Feedback)102.24 kB--
@sentry/browser (incl. Feedback)44.51 kB--
@sentry/browser (incl. sendFeedback)32.13 kB--
@sentry/browser (incl. FeedbackAsync)37.25 kB--
@sentry/browser (incl. Metrics)28.41 kB--
@sentry/browser (incl. Logs)28.64 kB--
@sentry/browser (incl. Metrics & Logs)29.33 kB--
@sentry/react29.05 kB--
@sentry/react (incl. Tracing)47.55 kB--
@sentry/vue32.24 kB--
@sentry/vue (incl. Tracing)47.17 kB--
@sentry/svelte27.35 kB--
CDN Bundle29.73 kB--
CDN Bundle (incl. Tracing)47.84 kB--
CDN Bundle (incl. Logs, Metrics)31.21 kB--
CDN Bundle (incl. Tracing, Logs, Metrics)49.09 kB--
CDN Bundle (incl. Replay, Logs, Metrics)70.53 kB--
CDN Bundle (incl. Tracing, Replay)85.34 kB--
CDN Bundle (incl. Tracing, Replay, Logs, Metrics)86.5 kB--
CDN Bundle (incl. Tracing, Replay, Feedback)91.2 kB--
CDN Bundle (incl. Tracing, Replay, Feedback, Logs, Metrics)92.37 kB--
CDN Bundle - uncompressed87.8 kB--
CDN Bundle (incl. Tracing) - uncompressed144.29 kB--
CDN Bundle (incl. Logs, Metrics) - uncompressed92.29 kB--
CDN Bundle (incl. Tracing, Logs, Metrics) - uncompressed148.05 kB--
CDN Bundle (incl. Replay, Logs, Metrics) - uncompressed217.02 kB--
CDN Bundle (incl. Tracing, Replay) - uncompressed263.07 kB--
CDN Bundle (incl. Tracing, Replay, Logs, Metrics) - uncompressed266.81 kB--
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed276.77 kB--
CDN Bundle (incl. Tracing, Replay, Feedback, Logs, Metrics) - uncompressed280.5 kB--
@sentry/nextjs (client)50.03 kB--
@sentry/sveltekit (client)45.8 kB--
@sentry/core/server76.48 kB--
@sentry/core/browser63.23 kB--
@sentry/node-core62.59 kB--
@sentry/node131.1 kB--
@sentry/node - without tracing75.02 kB--
@sentry/aws-serverless87.24 kB+0.01%+1 B 🔺
@sentry/cloudflare (withSentry) - minified173.52 kB+0.23%+390 B 🔺
@sentry/cloudflare (withSentry)433.52 kB+0.26%+1.09 kB 🔺

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JPeer264
JPeer264 approved these changes May 26, 2026
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Looks great. I also added a memory test to ensure we not introduce any other memory leaks in the future by accident

@logaretm
logaretm merged commit 1e0341d into developMay 26, 2026
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@logaretm
logaretm deleted the awad/js-2605-makeflushlock-grows-a-waituntil-wrapper-chain-on-every-init branch May 26, 2026 08:34
@sentry-release-botsentry-release-botBot mentioned this pull request May 26, 2026
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@JPeer264JPeer264 mentioned this pull request May 27, 2026
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JPeer264 added a commit that referenced this pull request May 28, 2026
@JPeer264
fix(cloudflare): Use original waitUntil to not create a deadlock (#21197
8a2a490
)
follow up to: #21156
This prevents a deadlock in the `waitUntil`, which happened in the
sentry-mcp:
<img width="972" height="119" alt="Screenshot 2026-05-27 at 17 04 19"
src="https://github.com/user-attachments/assets/18ec0f64-c766-4f6f-82a6-9453280668a5"
/>
@github-actionsgithub-actionsBot mentioned this pull request May 29, 2026
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@JPeer264JPeer264JPeer264 approved these changes
@andreiborzaandreiborzaAwaiting requested review from andreiborzaandreiborza is a code owner automatically assigned from getsentry/team-javascript-sdks-server

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makeFlushLock grows a waitUntil wrapper chain on every init(), causing stack overflow and memory exhaustion in Durable Objects

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@logaretm@JPeer264