feat: add sliding sync (MSC4186) implementation #3673
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This commit adds native sliding sync support to Dendrite, implementing MSC4186 (Simplified Sliding Sync). Key features include: - New v4 sync endpoint at /_matrix/client/unstable/org.matrix.simplified_msc3575/sync - Sliding window room list with sorting and filtering - Room subscriptions for detailed room data - Extensions: to_device, e2ee, account_data, receipts, typing - Persistent connection state tracking - Support for lazy-loading room members - MSC3266 room summary endpoint - MSC4115 membership on events Also includes various fixes and improvements to existing sync functionality.
This commit includes several fixes for sliding sync receipt handling: - Clear receipt delivery state for specific rooms when timeline expansion is detected, ensuring receipts are re-delivered when the client resets its view of the room (initial:true with expanded_timeline:true) - Clear all connection receipts on fresh sliding sync connections - Copy-forward room configs to prevent perpetual limited:true state - Serialize m.read.private receipts under the correct type key - Extract invite_room_state from federated invite events properly - Populate timeline/state for NEVER rooms in incremental sync - Copy forward stream states for unchanged rooms in sliding sync These fixes address stuck unread badges in clients when rooms are entered/exited and timeline expansion occurs. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This should fix element-hq#3669 We'd potentially send an empty string to `GenerateCreateContent`, even if we set the correct `roomVersion` before. ### Pull Request Checklist <!-- Please read https://matrix-org.github.io/dendrite/development/contributing before submitting your pull request --> * [x] I have added Go unit tests or [Complement integration tests](https://github.com/matrix-org/complement) for this PR _or_ I have justified why this PR doesn't need tests * [x] Pull request includes a [sign off below](https://element-hq.github.io/dendrite/development/contributing#sign-off) _or_ I have already signed off privately --------- Signed-off-by: Till Faelligen <2353100+S7evinK@users.noreply.github.com>
This is to complement the existing [Purge Room Admin API](https://element-hq.github.io/dendrite/administration/adminapi#post-_dendriteadminpurgeroomroomid) ### Pull Request Checklist <!-- Please read https://matrix-org.github.io/dendrite/development/contributing before submitting your pull request --> * [x] I have added Go unit tests or [Complement integration tests](https://github.com/matrix-org/complement) for this PR _or_ I have justified why this PR doesn't need tests * [x] Pull request includes a [sign off below](https://element-hq.github.io/dendrite/development/contributing#sign-off) _or_ I have already signed off privately --------- Signed-off-by: Till Faelligen <2353100+S7evinK@users.noreply.github.com>
Add GetLatestRoomConfigsBatch method to query multiple room configs in a single database query instead of N+1 queries. PostgreSQL uses DISTINCT ON for efficient single-query operation. SQLite falls back to iterating through rooms (acceptable for smaller deployments).
Refactor timeline expansion detection to use single batch query instead of N+1 pattern when processing room subscriptions.
Create single database snapshot for all filter operations in ApplyRoomFilters instead of creating N snapshots per room. Add WithSnapshot variants of getRoomName, isRoomEncrypted, and getRoomType to reuse the shared snapshot.
Add processListsAndCollectRooms and populateRoomDataForLists helper functions to eliminate ~120 lines of duplicated code between timeout and disconnect handlers. The helpers handle: - Processing room lists and collecting rooms that need data - Building room data for rooms in list operations
Add efficient delta operations for sliding sync room lists per MSC4186: - INSERT: Add room at specific index - DELETE: Remove room at specific index Implementation: - Add GenerateListOperations() to compute minimal operations - Detect insertions/deletions and order changes - Fall back to SYNC when changes exceed threshold (5 ops) - Update room tracking to handle INSERT operations This reduces bandwidth for incremental syncs when only a few rooms have changed position in the list.
Add spaces filtering support per MSC4186: - Query m.space.child state events from specified space rooms - Filter room list to include only direct children of those spaces - Child rooms are identified by state_key of m.space.child events - Only include children with valid "via" content (not removed) This allows clients to request rooms belonging to specific spaces using the "spaces" filter parameter.
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This PR adds MSC4186, following the initial work by @jackmaninov from the discussion in #3236 (comment).
A image for testing is available at pats22/dendrite:sliding-sync.
I've used this image in an Dendrite instance of mine and got sliding sync to work, incl. Element X compatibility.
fix #3236
In addition to the work by @jackmaninov, several improvements to performance and maintainability were made:
Performance Improvements
Maintainability Improvements
Protocol Completeness
INSERT/DELETElist operations for efficient incremental updates (previously only SYNC was implemented)m.space.childstate events (previously returned an error)Technical Details
INSERT/DELETE Operations:
Spaces Filtering:
Pull Request Checklist
Signed-off-by:
Patrick Schratz <pat-s@mailbox.org>