Skip to content

Serialize Dash._setup_server under a lock and publish its flag last #3980

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
mokashang wants to merge 3 commits into
base: dev
Choose a base branch
from
+472 −197
Open

Serialize Dash._setup_server under a lock and publish its flag last #3980

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
a90bfef
Serialize `Dash._setup_server` under a lock and publish its flag last
mokashang Sep 12, 2026
6ad48ed
Serialize router_sync and router_async under a lock, mirror _setup_se…
mokashang Sep 20, 2026
b980c87
Merge branch 'dev' into fix/setup-server-race-3971
T4rk1n Sep 21, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
1 change: 1 addition & 0 deletions CHANGELOG.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
- [#3986](https://github.com/plotly/dash/pull/3986) Adjust `_run_before_hooks` in the `fastapi` backend to honor a response returned by a `before_request` function, matching the `flask` backend's behavior.

### Fixed
- [#3980](https://github.com/plotly/dash/pull/3980) Fix the three `before_request` hooks (`Dash._setup_server` and the pages `router_sync` / `router_async`) publishing their "already done" guard flag before the setup work behind it had run. Under a multi-threaded WSGI worker such as `gunicorn -k gthread` (or under an ASGI worker for the async router), a second request arriving mid-setup could observe the flag already set, skip setup, then read `registered_paths` / `callback_map` / the pages router callback while they were still being registered - causing the first burst of component bundle requests after a restart to 500 with `Error loading dependency. "<lib>" is not a registered library`, or the pages router to hit `DuplicateCallback` when two workers raced past the guard. Each hook body now runs under a lock (`threading.Lock` for the two sync hooks, an `asyncio.Lock` bound to the running loop for the async router) and only publishes the flag after all work completes. Fixes [#3971](https://github.com/plotly/dash/issues/3971).
- [#3944](https://github.com/plotly/dash/pull/3944) Fix `dash.testing` runner backend detection for wrapped FastAPI/Quart servers so threaded Flask-only options are not passed to ASGI runners.
- [#3955](https://github.com/plotly/dash/pull/3955) Unpin `selenium` in the testing requirements (was capped at `<=4.2.0` from 2022) and require `>=4.11.0`, so it can drive current stable Chrome via Selenium Manager and stop the widespread CI flakiness.
- Speed up the renderer layout crawl (`crawlLayout` and its callers) by replacing curried-ramda `path`/`pathOr` lookups with direct property access on the hot path: ~16% faster `Patch().append()` into a large container, with no behavior change.
Expand Down
Loading
Loading