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Optimise backfill calculation #12522

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Apr 26, 2022
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Optimise backfill calculation #12522

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Apr 26, 2022

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@richvdh richvdh commented Apr 22, 2022 •
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Try to avoid an OOM by checking fewer extremities.

Generally this is a big rewrite of _maybe_backfill, to try and fix some of the TODOs and other problems in it. It's best reviewed commit-by-commit.

Fixes: #12523

@richvdh richvdh force-pushed the rav/optimise_maybe_backfill branch 2 times, most recently from 46a64f4 to 97bfe26 Compare April 25, 2022 11:30
@richvdh
skip a dict construction
cd4d26f 
we may as well just chain together the two inputs
@richvdh
Move some filtering and sorting logic earlier
9a68a56 
We can potentially skip some expensive db work by moving this synchronous code
earlier. The `sorted` might be expensive, but nowhere near as expensive as the
db lookups.
@richvdh
update some comments and logs
8843069
@richvdh
Use lists of tuples instead of Dicts
8feaece 
Both of these queries `GROUP BY b.event_id`, so there's no deduplication being
done, and the dict has no value for us.
@richvdh
Use an attrs to track backfill points
b945de6 
Tuples are annoying.
@richvdh
Bail out when we find a visible extremity
a1bd48f 
Rather than checking all of the backwards extremities (which may be legion), we
check one at a time and bail out as soon as we find a visible one
@richvdh
Use get_events_as_list
cb88081 
We don't need the dict here.
@richvdh
Include insertion events in the filtered_extremities checks
1f0a63e
@richvdh richvdh force-pushed the rav/optimise_maybe_backfill branch from 97bfe26 to 7e7adb6 Compare April 25, 2022 11:49
@richvdh richvdh marked this pull request as ready for review April 25, 2022 11:53
@richvdh richvdh requested a review from a team as a code owner April 25, 2022 11:53
@richvdh richvdh force-pushed the rav/optimise_maybe_backfill branch from 7e7adb6 to a23e5a1 Compare April 25, 2022 12:00
@DMRobertson DMRobertson self-assigned this Apr 25, 2022
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DMRobertson approved these changes Apr 25, 2022
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I'm a little unsure about the a couple of comments (see discussion of "filtering" and "successor events", but I think the logical changes are sound. I'm not too fussed about the Set versus List comment.

I'll leave those minor things to your discretion; otherwise LGTM.

synapse/handlers/federation.py Outdated Show resolved Hide resolved
richvdh and others added 2 commits April 25, 2022 18:12
@richvdh
Update synapse/handlers/federation.py
881d794 
Co-authored-by: David Robertson <davidr@element.io>
@richvdh
More comment updates, per review
8487963
richvdh and others added 2 commits April 25, 2022 18:15
@richvdh
Use a list rather than a set
b75b3f5 
It's impossible for us to have duplicates here, so we may as well use a boring
list.
@richvdh
Update and rename 12522.misc to 12522.bugfix
1dfe084
DMRobertson
DMRobertson reviewed Apr 25, 2022
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changelog.d/12522.bugfix
@@ -0,0 +1 @@
Fix a bug introduced in Synapse 0.99.3 which could cause Synapse to consume large amounts of RAM when back-paginating in a large room.
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Suppose we're in the worst case, where we have many backfill points to consider and none of them/their successor events are visible to us. Wouldn't we end up doing the same amount of work as before this change? (I.e. isn't this a bugfix for the best/average case rather than the worst?)

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Wouldn't we end up doing the same amount of work as before this change?

I think we won't try to load all state maps into memory at the same time (which we used to do in the depths of filter_events_for_server, in _event_to_memberships). So yeah, we might end up churning a bunch of CPU which we didn't before, but at least we won't OOM.

@richvdh richvdh merged commit 17d99f7 into develop Apr 26, 2022
@richvdh richvdh deleted the rav/optimise_maybe_backfill branch April 26, 2022 09:27
@MadLittleMods MadLittleMods added the A-Performance Performance, both client-facing and admin-facing label Apr 26, 2022
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synapse/handlers/federation.py
class _BackfillPointType(Enum):
# a regular backwards extremity (ie, an event which we don't yet have, but which
# is referred to by other events in the DAG)
BACKWARDS_EXTREMITY = enum.auto()
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@MadLittleMods MadLittleMods Apr 26, 2022 •
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I think "backward extremity" (not plural) is the correct spelling using the database as the source of truth (and the docs docs/development/room-dag-concepts.md#backward-extremity but I derived those from the code).

@reivilibre reivilibre mentioned this pull request Apr 27, 2022
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babolivier added a commit to matrix-org/synapse-dinsic that referenced this pull request Apr 28, 2022
@babolivier
Merge tag 'v1.58.0rc1' into babolivier/dinsic_1.58
066e2e0 
Synapse 1.58.0rc1 (2022-04-26)
==============================

As of this release, the groups/communities feature in Synapse is now disabled by default. See [\#11584](matrix-org/synapse#11584) for details. As mentioned in [the upgrade notes](https://github.com/matrix-org/synapse/blob/develop/docs/upgrade.md#upgrading-to-v1580), this feature will be removed in Synapse 1.61.

Features
--------

- Implement [MSC3383](matrix-org/matrix-spec-proposals#3383) for including the destination in server-to-server authentication headers. Contributed by @Bubu and @jcgruenhage for Famedly. ([\#11398](matrix-org/synapse#11398))
- Docker images and Debian packages from matrix.org now contain a locked set of Python dependencies, greatly improving build reproducibility. ([Board](https://github.com/orgs/matrix-org/projects/54), [\#11537](matrix-org/synapse#11537))
- Enable processing of device list updates asynchronously. ([\#12365](matrix-org/synapse#12365), [\#12465](matrix-org/synapse#12465))
- Implement [MSC2815](matrix-org/matrix-spec-proposals#2815) to allow room moderators to view redacted event content. Contributed by @tulir. ([\#12427](matrix-org/synapse#12427))
- Build Debian packages for Ubuntu 22.04 "Jammy Jellyfish". ([\#12543](matrix-org/synapse#12543))

Bugfixes
--------

- Prevent a sync request from removing a user's busy presence status. ([\#12213](matrix-org/synapse#12213))
- Fix bug with incremental sync missing events when rejoining/backfilling. Contributed by Nick @ Beeper. ([\#12319](matrix-org/synapse#12319))
- Fix a long-standing bug which incorrectly caused `GET /_matrix/client/v3/rooms/{roomId}/event/{eventId}` to return edited events rather than the original. ([\#12476](matrix-org/synapse#12476))
- Fix a bug introduced in Synapse 1.27.0 where the admin API for [deleting forward extremities](https://github.com/matrix-org/synapse/blob/erikj/fix_delete_event_response_count/docs/admin_api/rooms.md#deleting-forward-extremities) would always return a count of 1, no matter how many extremities were deleted. ([\#12496](matrix-org/synapse#12496))
- Fix a long-standing bug where the image thumbnails embedded into email notifications were broken. ([\#12510](matrix-org/synapse#12510))
- Fix a bug in the implementation of [MSC3202](matrix-org/matrix-spec-proposals#3202) where Synapse would use the field name `device_unused_fallback_keys`, rather than `device_unused_fallback_key_types`. ([\#12520](matrix-org/synapse#12520))
- Fix a bug introduced in Synapse 0.99.3 which could cause Synapse to consume large amounts of RAM when back-paginating in a large room. ([\#12522](matrix-org/synapse#12522))

Improved Documentation
----------------------

- Fix rendering of the documentation site when using the 'print' feature. ([\#12340](matrix-org/synapse#12340))
- Add a manual documenting config file options. ([\#12368](matrix-org/synapse#12368), [\#12527](matrix-org/synapse#12527))
- Update documentation to reflect that both the `run_background_tasks_on` option and the options for moving stream writers off of the main process are no longer experimental. ([\#12451](matrix-org/synapse#12451))
- Update worker documentation and replace old `federation_reader` with `generic_worker`. ([\#12457](matrix-org/synapse#12457))
- Strongly recommend [Poetry](https://python-poetry.org/) for development. ([\#12475](matrix-org/synapse#12475))
- Add some example configurations for workers and update architectural diagram. ([\#12492](matrix-org/synapse#12492))
- Fix a broken link in `README.rst`. ([\#12495](matrix-org/synapse#12495))
- Add HAProxy delegation example with CORS headers to docs. ([\#12501](matrix-org/synapse#12501))
- Remove extraneous comma in User Admin API's device deletion section so that the example JSON is actually valid and works. Contributed by @olmari. ([\#12533](matrix-org/synapse#12533))

Deprecations and Removals
-------------------------

- The groups/communities feature in Synapse is now disabled by default. ([\#12344](matrix-org/synapse#12344))
- Remove unstable identifiers from [MSC3440](matrix-org/matrix-spec-proposals#3440). ([\#12382](matrix-org/synapse#12382))

Internal Changes
----------------

- Preparation for faster-room-join work: start a background process to resynchronise the room state after a room join. ([\#12394](matrix-org/synapse#12394))
- Preparation for faster-room-join work: Implement a tracking mechanism to allow functions to wait for full room state to arrive. ([\#12399](matrix-org/synapse#12399))
- Remove an unstable identifier from [MSC3083](matrix-org/matrix-spec-proposals#3083). ([\#12395](matrix-org/synapse#12395))
- Run CI in the locked [Poetry](https://python-poetry.org/) environment, and remove corresponding `tox` jobs. ([\#12425](matrix-org/synapse#12425), [\#12434](matrix-org/synapse#12434), [\#12438](matrix-org/synapse#12438), [\#12441](matrix-org/synapse#12441), [\#12449](matrix-org/synapse#12449), [\#12478](matrix-org/synapse#12478), [\#12514](matrix-org/synapse#12514), [\#12472](matrix-org/synapse#12472))
- Change Mutual Rooms' `unstable_features` flag to `uk.half-shot.msc2666.mutual_rooms` which matches the current iteration of [MSC2666](matrix-org/matrix-spec-proposals#2666). ([\#12445](matrix-org/synapse#12445))
- Fix typo in the release script help string. ([\#12450](matrix-org/synapse#12450))
- Fix a minor typo in the Debian changelogs generated by the release script. ([\#12497](matrix-org/synapse#12497))
- Reintroduce the list of targets to the linter script, to avoid linting unwanted local-only directories during development. ([\#12455](matrix-org/synapse#12455))
- Limit length of `device_id` to less than 512 characters. ([\#12454](matrix-org/synapse#12454))
- Dockerfile-workers: reduce the amount we install in the image. ([\#12464](matrix-org/synapse#12464))
- Dockerfile-workers: give the master its own log config. ([\#12466](matrix-org/synapse#12466))
- complement-synapse-workers: factor out separate entry point script. ([\#12467](matrix-org/synapse#12467))
- Back out experimental implementation of [MSC2314](matrix-org/matrix-spec-proposals#2314). ([\#12474](matrix-org/synapse#12474))
- Fix grammatical error in federation error response when the room version of a room is unknown. ([\#12483](matrix-org/synapse#12483))
- Remove unnecessary configuration overrides in tests. ([\#12511](matrix-org/synapse#12511))
- Refactor the relations code for clarity. ([\#12519](matrix-org/synapse#12519))
- Add type hints so `docker` and `stubs` directories pass `mypy --disallow-untyped-defs`. ([\#12528](matrix-org/synapse#12528))
- Update `delay_cancellation` to accept any awaitable, rather than just `Deferred`s. ([\#12468](matrix-org/synapse#12468))
- Handle cancellation in `EventsWorkerStore._get_events_from_cache_or_db`. ([\#12529](matrix-org/synapse#12529))
babolivier added a commit to matrix-org/synapse-dinsic that referenced this pull request May 3, 2022
@babolivier
Merge tag 'v1.58.0' into babolivier/dinsic_1.58
21daaa7 
Synapse 1.58.0 (2022-05-03)
===========================

As of this release, the groups/communities feature in Synapse is now disabled by default. See [\#11584](matrix-org/synapse#11584) for details. As mentioned in [the upgrade notes](https://github.com/matrix-org/synapse/blob/develop/docs/upgrade.md#upgrading-to-v1580), this feature will be removed in Synapse 1.61.

No significant changes since 1.58.0rc2.

Synapse 1.58.0rc2 (2022-04-26)
==============================

This release candidate fixes bugs related to Synapse 1.58.0rc1's logic for handling device list updates.

Bugfixes
--------

- Fix a bug introduced in Synapse 1.58.0rc1 where the main process could consume excessive amounts of CPU and memory while handling sentry logging failures. ([\#12554](matrix-org/synapse#12554))
- Fix a bug introduced in Synapse 1.58.0rc1 where opentracing contexts were not correctly sent to whitelisted remote servers with device lists updates. ([\#12555](matrix-org/synapse#12555))

Internal Changes
----------------

- Reduce unnecessary work when handling remote device list updates. ([\#12557](matrix-org/synapse#12557))

Synapse 1.58.0rc1 (2022-04-26)
==============================

Features
--------

- Implement [MSC3383](matrix-org/matrix-spec-proposals#3383) for including the destination in server-to-server authentication headers. Contributed by @Bubu and @jcgruenhage for Famedly. ([\#11398](matrix-org/synapse#11398))
- Docker images and Debian packages from matrix.org now contain a locked set of Python dependencies, greatly improving build reproducibility. ([Board](https://github.com/orgs/matrix-org/projects/54), [\#11537](matrix-org/synapse#11537))
- Enable processing of device list updates asynchronously. ([\#12365](matrix-org/synapse#12365), [\#12465](matrix-org/synapse#12465))
- Implement [MSC2815](matrix-org/matrix-spec-proposals#2815) to allow room moderators to view redacted event content. Contributed by @tulir @ Beeper. ([\#12427](matrix-org/synapse#12427))
- Build Debian packages for Ubuntu 22.04 "Jammy Jellyfish". ([\#12543](matrix-org/synapse#12543))

Bugfixes
--------

- Prevent a sync request from removing a user's busy presence status. ([\#12213](matrix-org/synapse#12213))
- Fix bug with incremental sync missing events when rejoining/backfilling. Contributed by Nick @ Beeper. ([\#12319](matrix-org/synapse#12319))
- Fix a long-standing bug which incorrectly caused `GET /_matrix/client/v3/rooms/{roomId}/event/{eventId}` to return edited events rather than the original. ([\#12476](matrix-org/synapse#12476))
- Fix a bug introduced in Synapse 1.27.0 where the admin API for [deleting forward extremities](https://github.com/matrix-org/synapse/blob/erikj/fix_delete_event_response_count/docs/admin_api/rooms.md#deleting-forward-extremities) would always return a count of 1, no matter how many extremities were deleted. ([\#12496](matrix-org/synapse#12496))
- Fix a long-standing bug where the image thumbnails embedded into email notifications were broken. ([\#12510](matrix-org/synapse#12510))
- Fix a bug in the implementation of [MSC3202](matrix-org/matrix-spec-proposals#3202) where Synapse would use the field name `device_unused_fallback_keys`, rather than `device_unused_fallback_key_types`. ([\#12520](matrix-org/synapse#12520))
- Fix a bug introduced in Synapse 0.99.3 which could cause Synapse to consume large amounts of RAM when back-paginating in a large room. ([\#12522](matrix-org/synapse#12522))

Improved Documentation
----------------------

- Fix rendering of the documentation site when using the 'print' feature. ([\#12340](matrix-org/synapse#12340))
- Add a manual documenting config file options. ([\#12368](matrix-org/synapse#12368), [\#12527](matrix-org/synapse#12527))
- Update documentation to reflect that both the `run_background_tasks_on` option and the options for moving stream writers off of the main process are no longer experimental. ([\#12451](matrix-org/synapse#12451))
- Update worker documentation and replace old `federation_reader` with `generic_worker`. ([\#12457](matrix-org/synapse#12457))
- Strongly recommend [Poetry](https://python-poetry.org/) for development. ([\#12475](matrix-org/synapse#12475))
- Add some example configurations for workers and update architectural diagram. ([\#12492](matrix-org/synapse#12492))
- Fix a broken link in `README.rst`. ([\#12495](matrix-org/synapse#12495))
- Add HAProxy delegation example with CORS headers to docs. ([\#12501](matrix-org/synapse#12501))
- Remove extraneous comma in User Admin API's device deletion section so that the example JSON is actually valid and works. Contributed by @olmari. ([\#12533](matrix-org/synapse#12533))

Deprecations and Removals
-------------------------

- The groups/communities feature in Synapse is now disabled by default. ([\#12344](matrix-org/synapse#12344))
- Remove unstable identifiers from [MSC3440](matrix-org/matrix-spec-proposals#3440). ([\#12382](matrix-org/synapse#12382))

Internal Changes
----------------

- Preparation for faster-room-join work: start a background process to resynchronise the room state after a room join. ([\#12394](matrix-org/synapse#12394))
- Preparation for faster-room-join work: Implement a tracking mechanism to allow functions to wait for full room state to arrive. ([\#12399](matrix-org/synapse#12399))
- Remove an unstable identifier from [MSC3083](matrix-org/matrix-spec-proposals#3083). ([\#12395](matrix-org/synapse#12395))
- Run CI in the locked [Poetry](https://python-poetry.org/) environment, and remove corresponding `tox` jobs. ([\#12425](matrix-org/synapse#12425), [\#12434](matrix-org/synapse#12434), [\#12438](matrix-org/synapse#12438), [\#12441](matrix-org/synapse#12441), [\#12449](matrix-org/synapse#12449), [\#12478](matrix-org/synapse#12478), [\#12514](matrix-org/synapse#12514), [\#12472](matrix-org/synapse#12472))
- Change Mutual Rooms' `unstable_features` flag to `uk.half-shot.msc2666.mutual_rooms` which matches the current iteration of [MSC2666](matrix-org/matrix-spec-proposals#2666). ([\#12445](matrix-org/synapse#12445))
- Fix typo in the release script help string. ([\#12450](matrix-org/synapse#12450))
- Fix a minor typo in the Debian changelogs generated by the release script. ([\#12497](matrix-org/synapse#12497))
- Reintroduce the list of targets to the linter script, to avoid linting unwanted local-only directories during development. ([\#12455](matrix-org/synapse#12455))
- Limit length of `device_id` to less than 512 characters. ([\#12454](matrix-org/synapse#12454))
- Dockerfile-workers: reduce the amount we install in the image. ([\#12464](matrix-org/synapse#12464))
- Dockerfile-workers: give the master its own log config. ([\#12466](matrix-org/synapse#12466))
- complement-synapse-workers: factor out separate entry point script. ([\#12467](matrix-org/synapse#12467))
- Back out experimental implementation of [MSC2314](matrix-org/matrix-spec-proposals#2314). ([\#12474](matrix-org/synapse#12474))
- Fix grammatical error in federation error response when the room version of a room is unknown. ([\#12483](matrix-org/synapse#12483))
- Remove unnecessary configuration overrides in tests. ([\#12511](matrix-org/synapse#12511))
- Refactor the relations code for clarity. ([\#12519](matrix-org/synapse#12519))
- Add type hints so `docker` and `stubs` directories pass `mypy --disallow-untyped-defs`. ([\#12528](matrix-org/synapse#12528))
- Update `delay_cancellation` to accept any awaitable, rather than just `Deferred`s. ([\#12468](matrix-org/synapse#12468))
- Handle cancellation in `EventsWorkerStore._get_events_from_cache_or_db`. ([\#12529](matrix-org/synapse#12529))
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Pagination in a large room with restricted visibility can cause an OOM
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