dendrite/roomserver
Till 5267cc0f54
Optimise getting local members and membership counts (#3150)
The previous version was getting **ALL** membership events (as
`ClientEvents`, so going through `NewEventFromTrustedJSONWithID`) for a
given room.
Now we are querying only locally joined users as `ClientEvents`, which
should **significantly** reduce allocations.

Take for example a large room with 2k membership events, but only 1
local user - avoiding 1999 `NewEventFromTrustedJSONWithID` calls just to
calculate the `roomSize` which we can also query by other means.

This is also getting called for every `OutputRoomEvent` in the userAPI.

Benchmark with 1 local user and 100 remote users.
```
pkg: github.com/matrix-org/dendrite/userapi/consumers
cpu: 12th Gen Intel(R) Core(TM) i5-12500H
                    │   old.txt   │               new.txt               │
                    │   sec/op    │   sec/op     vs base                │
LocalRoomMembers-16   375.9µ ± 7%   327.6µ ± 6%  -12.85% (p=0.000 n=10)

                    │    old.txt    │               new.txt                │
                    │     B/op      │     B/op      vs base                │
LocalRoomMembers-16   79.426Ki ± 0%   8.507Ki ± 0%  -89.29% (p=0.000 n=10)

                    │   old.txt   │              new.txt               │
                    │  allocs/op  │ allocs/op   vs base                │
LocalRoomMembers-16   1015.0 ± 0%   277.0 ± 0%  -72.71% (p=0.000 n=10)
```
2023-07-13 14:19:08 +02:00
..
acls Use PDU not *Event in HeaderedEvent (#3073) 2023-05-02 15:03:16 +01:00
api Optimise getting local members and membership counts (#3150) 2023-07-13 14:19:08 +02:00
auth Fix backfilling (#3117) 2023-06-20 16:52:29 +02:00
internal Optimise getting local members and membership counts (#3150) 2023-07-13 14:19:08 +02:00
producers PDU Sender split (#3100) 2023-06-06 20:55:18 +00:00
state Merge SenderID & Per Room User Key work (#3109) 2023-06-14 14:23:46 +00:00
storage Fix adding state events to the database (#3133) 2023-07-04 17:15:44 +02:00
types Add MXIDMapping for pseudoID rooms (#3112) 2023-06-28 20:29:49 +02:00
version Use IRoomVersion (#3064) 2023-04-24 11:50:37 +01:00
README.md use go module for dependencies (#594) 2019-05-21 21:56:55 +01:00
roomserver_test.go Add MXIDMapping for pseudoID rooms (#3112) 2023-06-28 20:29:49 +02:00
roomserver.go Remove BaseDendrite (#3023) 2023-03-22 09:21:32 +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 |
+---------------+-------------------+------------------+----------+