Yield to reactor in large loops#19507
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erikjohnston merged 4 commits intodevelopfrom Mar 2, 2026
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When a worker gets very busy some of these loops can get large and end up taking hundreds of ms to complete. To help keep the reactor tick times reasonable we add a periodic yield into these loops.
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This PR contains the following updates: | Package | Update | Change | |---|---|---| | [element-hq/synapse](https://github.com/element-hq/synapse) | minor | `v1.148.0` → `v1.149.0` | --- ### Release Notes <details> <summary>element-hq/synapse (element-hq/synapse)</summary> ### [`v1.149.0`](https://github.com/element-hq/synapse/releases/tag/v1.149.0) [Compare Source](element-hq/synapse@v1.148.0...v1.149.0) ### Synapse 1.149.0 (2026-03-10) No significant changes since 1.149.0rc1. ### Synapse 1.149.0rc1 (2026-03-03) #### Features - Add experimental support for [MSC4388: Secure out-of-band channel for sign in with QR](matrix-org/matrix-spec-proposals#4388). ([#​19127](element-hq/synapse#19127)) - Add stable support for [MSC4380](matrix-org/matrix-spec-proposals#4380) invite blocking. ([#​19431](element-hq/synapse#19431)) #### Bugfixes - Fix the 'Login as a user' Admin API not checking if the user exists before issuing an access token. ([#​18518](element-hq/synapse#18518)) - Fix `/sync` missing membership event in `state_after` (experimental [MSC4222](matrix-org/matrix-spec-proposals#4222) implementation) in some scenarios. ([#​19460](element-hq/synapse#19460)) #### Internal Changes - Add log to explain when and why we freeze objects in the garbage collector. ([#​19440](element-hq/synapse#19440)) - Better instrument `JoinRoomAliasServlet` with tracing. ([#​19461](element-hq/synapse#19461)) - Fix Complement CI not running against the code from our PRs. ([#​19475](element-hq/synapse#19475)) - Log `docker system info` in CI so we have a plain record of how GitHub runners evolve over time. ([#​19480](element-hq/synapse#19480)) - Rename the `test_disconnect` test helper so that pytest doesn't see it as a test. ([#​19486](element-hq/synapse#19486)) - Add a log line when we delete devices. Contributed by [@​bradtgmurray](https://github.com/bradtgmurray) @​ Beeper. ([#​19496](element-hq/synapse#19496)) - Pre-allocate the buffer based on the expected `Content-Length` with the Rust HTTP client. ([#​19498](element-hq/synapse#19498)) - Cancel long-running sync requests if the client has gone away. ([#​19499](element-hq/synapse#19499)) - Try and reduce reactor tick times when under heavy load. ([#​19507](element-hq/synapse#19507)) - Simplify Rust HTTP client response streaming and limiting. ([#​19510](element-hq/synapse#19510)) - Replace deprecated collection import locations with current locations. ([#​19515](element-hq/synapse#19515)) - Bump most locked Python dependencies to their latest versions. ([#​19519](element-hq/synapse#19519)) </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR is behind base branch, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate). <!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0My41OS4yIiwidXBkYXRlZEluVmVyIjoiNDMuNTkuMiIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOlsiaW1hZ2UiXX0=--> Reviewed-on: https://gitea.alexlebens.dev/alexlebens/infrastructure/pulls/4580 Co-authored-by: Renovate Bot <renovate-bot@alexlebens.net> Co-committed-by: Renovate Bot <renovate-bot@alexlebens.net>
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When a worker gets very busy some of these loops can get large and end up taking hundreds of ms to complete. To help keep the reactor tick times reasonable we add a periodic yield into these loops.
These were found by doing a
py-spyand speedscope.net (in time order) to see where we were spending blocks of time