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Log if we ever gc.freeze()#19440

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Feb 25, 2026
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Log if we ever gc.freeze()#19440
MadLittleMods merged 2 commits intodevelopfrom
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@MadLittleMods MadLittleMods commented Feb 6, 2026 •
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Log if we ever gc.freeze()

Spawning from https://github.com/element-hq/synapse-small-hosts/issues/348 where some test appears to be flaky because some homeserver objects are frozen in the garbage collector.

We set freeze=False in the Synapse Pro for small hosts code but I just want to use this log to make extra sure this isn't being run somehow. The follow-up here would be to see what else would cause something to be frozen in the garbage collector.

Dev notes

Original issue that proposes the gc.freeze() API, https://bugs.python.org/issue31558

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MadLittleMods
MadLittleMods commented Feb 6, 2026
View reviewed changes
synapse/app/_base.py
Comment on lines +779 to +783
logger.info(
"garbage collector: Freezing all allocated objects in the hopes that (almost) "
"everything currently allocated are things that will be used by the homeserver "
"for the rest of time. Doing so means less work each GC (hopefully)."
)
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This is the same language used in the comment above. I think it's worth having some explanation here.

@MadLittleMods MadLittleMods marked this pull request as ready for review February 9, 2026 14:45
@MadLittleMods MadLittleMods requested a review from a team as a code owner February 9, 2026 14:45
@MadLittleMods MadLittleMods merged commit ac3a115 into develop Feb 25, 2026
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@MadLittleMods MadLittleMods deleted the madlittlemods/log-freeze branch February 25, 2026 15:47
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MadLittleMods commented Feb 25, 2026

Thanks for the review @sandhose 🦔

alexlebens pushed a commit to alexlebens/infrastructure that referenced this pull request Mar 10, 2026
@alexlebens
chore(deps): update dependency element-hq/synapse to v1.149.0 (#4580)
159eef8 
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). ([#&#8203;19127](element-hq/synapse#19127))
- Add stable support for [MSC4380](matrix-org/matrix-spec-proposals#4380) invite blocking. ([#&#8203;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. ([#&#8203;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. ([#&#8203;19460](element-hq/synapse#19460))

#### Internal Changes

- Add log to explain when and why we freeze objects in the garbage collector. ([#&#8203;19440](element-hq/synapse#19440))
- Better instrument `JoinRoomAliasServlet` with tracing. ([#&#8203;19461](element-hq/synapse#19461))
- Fix Complement CI not running against the code from our PRs. ([#&#8203;19475](element-hq/synapse#19475))
- Log `docker system info` in CI so we have a plain record of how GitHub runners evolve over time. ([#&#8203;19480](element-hq/synapse#19480))
- Rename the `test_disconnect` test helper so that pytest doesn't see it as a test. ([#&#8203;19486](element-hq/synapse#19486))
- Add a log line when we delete devices. Contributed by [@&#8203;bradtgmurray](https://github.com/bradtgmurray) @&#8203; Beeper. ([#&#8203;19496](element-hq/synapse#19496))
- Pre-allocate the buffer based on the expected `Content-Length` with the Rust HTTP client. ([#&#8203;19498](element-hq/synapse#19498))
- Cancel long-running sync requests if the client has gone away. ([#&#8203;19499](element-hq/synapse#19499))
- Try and reduce reactor tick times when under heavy load. ([#&#8203;19507](element-hq/synapse#19507))
- Simplify Rust HTTP client response streaming and limiting. ([#&#8203;19510](element-hq/synapse#19510))
- Replace deprecated collection import locations with current locations. ([#&#8203;19515](element-hq/synapse#19515))
- Bump most locked Python dependencies to their latest versions. ([#&#8203;19519](element-hq/synapse#19519))

</details>

---

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This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0My41OS4yIiwidXBkYXRlZEluVmVyIjoiNDMuNTkuMiIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOlsiaW1hZ2UiXX0=-->

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