dendrite/roomserver
Till f93d1c4790
Use AckExplicitPolicy instead of AckAllPolicy (#3288)
Fixes https://github.com/matrix-org/dendrite/issues/3240 and potentially
a root cause for state resets.

While testing, I've had added some more debug logging:
```
time="2023-12-16T18:13:11.319458084Z" level=warning msg="already processed event" event_id="$qFYMl_F2vb1N0yxmvlFAMhqhGhLKq4kA-o_YCQKH7tQ" kind=KindNew times=2
time="2023-12-16T18:13:14.537389126Z" level=warning msg="already processed event" event_id="$EU-LTsKErT6Mt1k12-p_3xOHfiLaK6gtwVDlZ35lSuo" kind=KindNew times=5
time="2023-12-16T18:13:16.789551206Z" level=warning msg="already processed event" event_id="$dIPuAfTL5x0VyG873LKPslQeljCSxFT1WKxUtjIMUGE" kind=KindNew times=5
time="2023-12-16T18:13:17.383838767Z" level=warning msg="already processed event" event_id="$7noSZiCkzerpkz_UBO3iatpRnaOiPx-3IXc0GPDQVGE" kind=KindNew times=2
time="2023-12-16T18:13:22.091946597Z" level=warning msg="already processed event" event_id="$3Lvo3Wbi2ol9-nNbQ93N-E2MuGQCJZo5397KkFH-W6E" kind=KindNew times=1
time="2023-12-16T18:13:23.026417446Z" level=warning msg="already processed event" event_id="$lj1xS46zsLBCChhKOLJEG-bu7z-_pq9i_Y2DUIjzGy4" kind=KindNew times=4
```

So we did receive the same event over and over again. Given they are
`KindNew`, we don't short circuit if we already processed them, which
potentially caused the state to be calculated with a now wrong state
snapshot.

Also fixes the back pressure metric. We now correctly increment the
counter once we sent the message to NATS and decrement it once we
actually processed an event.
2023-12-19 08:25:47 +01:00
..
acls Update ACLs when received as outliers (#3008) 2023-11-22 15:38:04 +01:00
api Update gmsl to use new validated RoomID on PDUs (#3200) 2023-09-15 14:39:06 +00:00
auth Update gmsl to use new validated RoomID on PDUs (#3200) 2023-09-15 14:39:06 +00:00
internal Use AckExplicitPolicy instead of AckAllPolicy (#3288) 2023-12-19 08:25:47 +01:00
producers Update ACLs when received as outliers (#3008) 2023-11-22 15:38:04 +01:00
state Check event is not rejected (#3243) 2023-10-25 09:47:21 +02:00
storage Update ACLs when received as outliers (#3008) 2023-11-22 15:38:04 +01:00
types de-MSC-ifying space summaries (MSC2946) (#3134) 2023-07-20 15:06:05 +01:00
version Add config key for default room version (#3171) 2023-08-08 14:20:05 +01:00
README.md use go module for dependencies (#594) 2019-05-21 21:56:55 +01:00
roomserver_test.go Use AckExplicitPolicy instead of AckAllPolicy (#3288) 2023-12-19 08:25:47 +01:00
roomserver.go de-MSC-ifying space summaries (MSC2946) (#3134) 2023-07-20 15:06:05 +01:00

RoomServer

RoomServer Internals

Numeric IDs

To save space matrix string identifiers are mapped to local numeric IDs. The numeric IDs are more efficient to manipulate and use less space to store. The numeric IDs are never exposed in the API the room server exposes. The numeric IDs are converted to string IDs before they leave the room server. The numeric ID for a string ID is never 0 to avoid being confused with go's default zero value. Zero is used to indicate that there was no corresponding string ID. Well-known event types and event state keys are preassigned numeric IDs.

State Snapshot Storage

The room server stores the state of the matrix room at each event. For efficiency the state is stored as blocks of 3-tuples of numeric IDs for the event type, event state key and event ID. For further efficiency the state snapshots are stored as the combination of up to 64 these blocks. This allows blocks of the room state to be reused in multiple snapshots.

The resulting database tables look something like this:

+-------------------------------------------------------------------+
| Events                                                            |
+---------+-------------------+------------------+------------------+
| EventNID| EventTypeNID      | EventStateKeyNID | StateSnapshotNID |
+---------+-------------------+------------------+------------------+
|       1 | m.room.create   1 | ""             1 | <nil>          0 |
|       2 | m.room.member   2 | "@user:foo"    2 | <nil>          0 |
|       3 | m.room.member   2 | "@user:bar"    3 | {1,2}          1 |
|       4 | m.room.message  3 | <nil>          0 | {1,2,3}        2 |
|       5 | m.room.member   2 | "@user:foo"    2 | {1,2,3}        2 |
|       6 | m.room.message  3 | <nil>          0 | {1,3,6}        3 |
+---------+-------------------+------------------+------------------+

+----------------------------------------+
| State Snapshots                        |
+-----------------------+----------------+
| EventStateSnapshotNID | StateBlockNIDs |
+-----------------------+----------------|
|                     1 |           {1}  |
|                     2 |         {1,2}  |
|                     3 |       {1,2,3}  |
+-----------------------+----------------+

+-----------------------------------------------------------------+
| State Blocks                                                    |
+---------------+-------------------+------------------+----------+
| StateBlockNID | EventTypeNID      | EventStateKeyNID | EventNID |
+---------------+-------------------+------------------+----------+
|             1 | m.room.create   1 | ""             1 |        1 |
|             1 | m.room.member   2 | "@user:foo"    2 |        2 |
|             2 | m.room.member   2 | "@user:bar"    3 |        3 |
|             3 | m.room.member   2 | "@user:foo"    2 |        6 |
+---------------+-------------------+------------------+----------+