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dendrite/roomserver
Neil Alexander a466e9e9cc
LRU cache for room versions in RS query API (#976)
* Experimental LRU cache for room versions

* Don't accidentally try to type-assert nil

* Also reduce hits on query API

* Use hashicorp implementation which mutexes for us

* Define const for max cache entries

* Rename to be specifically immutable, panic if we try to mutate a cache entry

* Review comments

* Remove nil guards, give roomserver integration test a cache

* go mod tidy
2020-04-22 13:00:05 +01:00
..
alias Move /room/{roomID}/state endpoints into client API (#606) (#962) 2020-04-14 18:36:08 +01:00
api LRU cache for room versions in RS query API (#976) 2020-04-22 13:00:05 +01:00
auth Implement backfill over federation (#938) 2020-03-24 12:20:10 +00:00
input Invites v2 endpoint (#952) 2020-04-03 14:29:06 +01:00
query LRU cache for room versions in RS query API (#976) 2020-04-22 13:00:05 +01:00
state Federation for v3/v4 rooms (#954) 2020-04-09 15:46:06 +01:00
storage Set default room version to 4 (#957) 2020-04-16 12:53:27 +01:00
types Invites v2 endpoint (#952) 2020-04-03 14:29:06 +01:00
version Set default room version to 4 (#957) 2020-04-16 12:53:27 +01:00
README.md use go module for dependencies (#594) 2019-05-21 21:56:55 +01:00
roomserver.go LRU cache for room versions in RS query API (#976) 2020-04-22 13:00:05 +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 |
+---------------+-------------------+------------------+----------+