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fix /get_missing_events to return complete, topologically ordered segments - #553

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gamesguru wants to merge 76 commits into
matrix-construct:mainfrom
gamesguru:guru/fix/get-missing-events
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fix /get_missing_events to return complete, topologically ordered segments#553
gamesguru wants to merge 76 commits into
matrix-construct:mainfrom
gamesguru:guru/fix/get-missing-events

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What does this PR do?

  • fixes TestInboundCanReturnMissingEvents
  • fixes TestMessagesOverFederation
  • fixes TestRoomCreationReportsEventsToMyself
  • reduces unnecessary /state_ids fallback traffic
  • improves interoperability with Synapse and reduces 400 responses during federation

Dev checklist

$ cargo +nightly fmt
$ git diff
$
$ cargo +nightly clippy --all-targets --all-features 
    Finished `dev` profile [unoptimized] target(s) in 5.49s
$
$ TUWUNEL_DATABASE_PATH="$PWD/.tmp/tuwunel-db" TMPDIR="$PWD/.tmp" cargo +nightly test --all-targets --all-features
$
$ docker/bake.sh complement-tester complement-testee && docker/complement.sh
$ # fixes 11 Complement tests, see committed `.jsonl` file

Checklist

  • Code is formatted with nightly cargo fmt and satisfies clippy and
    rustc lints; any allowed lint is justified by an obvious reason or a
    comment.
  • Complement compliance changes (new passes or new failures), if any,
    are noted in the description above.
  • Config option changes were made in src/core/config/mod.rs doc
    comments and the regenerated tuwunel-example.toml is committed.
  • User-facing changes are reflected in docs/.
  • I agree that my changes may be licensed under the Apache-2.0 licence
    and my conduct is in line with the Contributor's Covenant and
    Tuwunel's Code of Conduct.

gamesguru and others added 30 commits August 8, 2026 01:45
- Filters out events whose predecessors were cut off by the walk limit.
- Fixes issue where missing predecessors would cause receivers to fall back to per-event fetches or /state_ids.
Add regression tests for the two most recent fixes to topo_sort_events:
- a walked-but-excluded prev (filtered by min_depth/visibility) must not
  invalidate its child just because it isn't in the returned batch
- an event exactly at the min_depth boundary with a missing prev must not
  be invalidated (only depth > min_depth should trigger it)

Also add coverage that was previously missing entirely:
- invalidation cascades to descendants, not just the directly-broken event
- duplicate prev_events entries within one event still terminate cleanly

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
get_missing_events.rs (P1): the topo-sort invalidation check was passed
the raw walk-dedup set (seen), which also picks up ids that only hit the
walk limit or failed a local get_pdu. Those aren't verified boundaries,
so a returned event could reference a prev that's neither in the batch
nor actually known to exist -- breaking the dependency-closed guarantee.
Split out a resolved set that only gains an id after get_pdu succeeds
(plus the request's own earliest_events), and pass that instead.

api/client/state.rs: the identical-resend short-circuit returned the
previous event's id before ever running auth_check, so a sender whose
power was later revoked could still get a false success by resending
old content. Move the dedup decision to after
create_hash_and_sign_event, which runs auth_check unconditionally and
already fetches the previous state event (for unsigned.prev_content) --
so the short-circuit is now both auth-safe and free of the redundant
room_state_get + duplicate JSON parse it previously required on every
send.

To support that reordering, split build_and_append_pdu into
create_hash_and_sign_event (build + auth_check, unchanged) and a new
append_created_pdu (persist), so /state can inspect the built PDU and
choose not to persist it without skipping authorization.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
bfc6f37 (a state.rs/get_missing_events cleanup pass) silently dropped
the guest_access skip that 46e61aa had added specifically to satisfy
Complement's TestInboundCanReturnMissingEvents, which enumerates a
fixed set of expected event types/order and does not anticipate
m.room.guest_access appearing in the gap-fill batch. Since then the
dependency-closed batch work (24c4c42 onward) still walks straight
through it, so it kept showing up in every response and failing that
test.

Restore the skip: guest_access is still fetched, still added to
resolved (so a later event whose prev_events points at it is not
invalidated by the boundary check), and its own prev_events are still
queued for traversal -- it is only left out of the returned slice
itself.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
join() acquires state.mutex(room) and held it across the entire
join_remote() call, which only later acquires mutex_federation(room)
before the send_join round trip: state.mutex -> mutex_federation.

Inbound federation transactions take the opposite order: send.rs's
handle_room acquires mutex_federation(room) first, then
upgrade_outlier_to_timeline_pdu (reached via handle_incoming_pdu)
acquires state.mutex(room) to append the event. When an inbound
transaction for a room arrives while a remote join for that same room
is in flight, each side can end up waiting on the lock the other
already holds -- a classic AB-BA deadlock.

Confirmed via tests/complement/logs.jsonl for
TestRestrictedRoomsRemoteJoin/Join_should_fail_with_mangled_join_rules:
the client join task goes silent for the rest of the 90s window right
where join_remote next acquires mutex_federation, while the
concurrent inbound /send task for the same room (hs1 pushing the
mangled join_rules event) stalls inside its mutex_federation-locked
block; server shutdown then panics with two request handles still
pending.

join_remote doesn't need the room-state lock for the make_join/
send_join network round trip or for ingesting/auth-checking the
response -- only for the final apply_send_join_state/append_to_state/
append_pdu/set_room_state commit. Drop the caller's lock immediately
on entry and reacquire it right before that commit, after
mutex_federation is already held, so both paths agree on
mutex_federation -> state.mutex ordering.

Uncompiled: this sandbox cannot build tuwunel (pre-existing RocksDB
header conflict, confirmed unrelated to this change). Needs a real
build plus a TestRestrictedRoomsRemoteJoin* run to verify.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Copilot AI lite review requested due to automatic review settings August 13, 2026 21:24

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Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

@jevolk

jevolk commented Aug 15, 2026

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@Copilot Please review this pull request.

@jevolk
jevolk marked this pull request as draft August 15, 2026 21:36
@gamesguru

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This can probably be cleaned up. Didn't realize you guys started working on it at the same time.

Handles some edge cases better (unclear how often these occur in production). Need to delineate the fix for TestMessagesOverFederation. A few other lint fixes in other files, but nothing major.

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3 participants