Commit Graph

17 Commits

Author SHA1 Message Date
Eric Eastwood
51d732db3b
Optimize how we calculate likely_domains during backfill (#13575)
Optimize how we calculate `likely_domains` during backfill because I've seen this take 17s in production just to `get_current_state` which is used to `get_domains_from_state` (see case [*2. Loading tons of events* in the `/messages` investigation issue](https://github.com/matrix-org/synapse/issues/13356)).

There are 3 ways we currently calculate hosts that are in the room:

 1. `get_current_state` -> `get_domains_from_state`
    - Used in `backfill` to calculate `likely_domains` and `/timestamp_to_event` because it was cargo-culted from `backfill`
    - This one is being eliminated in favor of `get_current_hosts_in_room` in this PR 🕳
 1. `get_current_hosts_in_room`
    - Used for other federation things like sending read receipts and typing indicators
 1. `get_hosts_in_room_at_events`
    - Used when pushing out events over federation to other servers in the `_process_event_queue_loop`

Fix https://github.com/matrix-org/synapse/issues/13626

Part of https://github.com/matrix-org/synapse/issues/13356

Mentioned in [internal doc](https://docs.google.com/document/d/1lvUoVfYUiy6UaHB6Rb4HicjaJAU40-APue9Q4vzuW3c/edit#bookmark=id.2tvwz3yhcafh)


### Query performance

#### Before

The query from `get_current_state` sucks just because we have to get all 80k events. And we see almost the exact same performance locally trying to get all of these events (16s vs 17s):
```
synapse=# SELECT type, state_key, event_id FROM current_state_events WHERE room_id = '!OGEhHVWSdvArJzumhm:matrix.org';
Time: 16035.612 ms (00:16.036)

synapse=# SELECT type, state_key, event_id FROM current_state_events WHERE room_id = '!OGEhHVWSdvArJzumhm:matrix.org';
Time: 4243.237 ms (00:04.243)
```

But what about `get_current_hosts_in_room`: When there is 8M rows in the `current_state_events` table, the previous query in `get_current_hosts_in_room` took 13s from complete freshness (when the events were first added). But takes 930ms after a Postgres restart or 390ms if running back to back to back.

```sh
$ psql synapse
synapse=# \timing on
synapse=# SELECT COUNT(DISTINCT substring(state_key FROM '@[^:]*:(.*)$'))
FROM current_state_events
WHERE
    type = 'm.room.member'
    AND membership = 'join'
    AND room_id = '!OGEhHVWSdvArJzumhm:matrix.org';
 count
-------
  4130
(1 row)

Time: 13181.598 ms (00:13.182)

synapse=# SELECT COUNT(*) from current_state_events where room_id = '!OGEhHVWSdvArJzumhm:matrix.org';
 count
-------
 80814

synapse=# SELECT COUNT(*) from current_state_events;
  count
---------
 8162847

synapse=# SELECT pg_size_pretty( pg_total_relation_size('current_state_events') );
 pg_size_pretty
----------------
 4702 MB
```

#### After

I'm not sure how long it takes from complete freshness as I only really get that opportunity once (maybe restarting computer but that's cumbersome) and it's not really relevant to normal operating times. Maybe you get closer to the fresh times the more access variability there is so that Postgres caches aren't as exact. Update: The longest I've seen this run for is 6.4s and 4.5s after a computer restart.

After a Postgres restart, it takes 330ms and running back to back takes 260ms.

```sh
$ psql synapse
synapse=# \timing on
Timing is on.
synapse=# SELECT
    substring(c.state_key FROM '@[^:]*:(.*)$') as host
FROM current_state_events c
/* Get the depth of the event from the events table */
INNER JOIN events AS e USING (event_id)
WHERE
    c.type = 'm.room.member'
    AND c.membership = 'join'
    AND c.room_id = '!OGEhHVWSdvArJzumhm:matrix.org'
GROUP BY host
ORDER BY min(e.depth) ASC;
Time: 333.800 ms
```

#### Going further

To improve things further we could add a `limit` parameter to `get_current_hosts_in_room`. Realistically, we don't need 4k domains to choose from because there is no way we're going to query that many before we a) probably get an answer or b) we give up. 

Another thing we can do is optimize the query to use a index skip scan:

 - https://wiki.postgresql.org/wiki/Loose_indexscan
 - Index Skip Scan, https://commitfest.postgresql.org/37/1741/
 - https://www.timescale.com/blog/how-we-made-distinct-queries-up-to-8000x-faster-on-postgresql/
2022-08-30 01:38:14 -05:00
Sean Quah
84169a82dc
Avoid blocking lazy-loading /syncs during partial joins (#13477)
Use a state filter or accept partial state in a few places where we
request state, to avoid blocking.

To make lazy-loading `/sync`s work, we need to provide the memberships
of event senders, which are not guaranteed to be in the room state.
Instead we dig through auth events for memberships to present to
clients. The auth events of an event are guaranteed to contain a
passable membership event, otherwise the event would have been rejected.

Note that this only covers the common code paths encountered during
testing. There has been no exhaustive checking of all sync code paths.

Fixes #13146.

Signed-off-by: Sean Quah <seanq@matrix.org>
2022-08-18 11:53:02 +01:00
Eric Eastwood
0a4efbc1dd
Instrument the federation/backfill part of /messages (#13489)
Instrument the federation/backfill part of `/messages` so it's easier to follow what's going on in Jaeger when viewing a trace.

Split out from https://github.com/matrix-org/synapse/pull/13440

Follow-up from https://github.com/matrix-org/synapse/pull/13368

Part of https://github.com/matrix-org/synapse/issues/13356
2022-08-16 12:39:40 -05:00
reivilibre
c3516e9dec
Faster room joins: make /joined_members block whilst the room is partial stated. (#13514) 2022-08-16 13:16:56 +01:00
Eric Eastwood
92d21faf12
Instrument /messages for understandable traces in Jaeger (#13368)
In Jaeger:

 - Before: huge list of uncategorized database calls
 - After: nice and collapsible into units of work
2022-08-03 10:57:38 -05:00
Sean Quah
224d792dd7
Refactor _resolve_state_at_missing_prevs to return an EventContext (#13404)
Previously, `_resolve_state_at_missing_prevs` returned the resolved
state before an event and a partial state flag. These were unwieldy to
carry around would only ever be used to build an event context. Build
the event context directly instead.

Signed-off-by: Sean Quah <seanq@matrix.org>
2022-08-01 13:53:56 +01:00
Sean Quah
335ebb21cc
Faster room joins: avoid blocking when pulling events with missing prevs (#13355)
Avoid blocking on full state in `_resolve_state_at_missing_prevs` and
return a new flag indicating whether the resolved state is partial.
Thread that flag around so that it makes it into the event context.

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
2022-07-26 12:39:23 +01:00
Erik Johnston
0731e0829c
Don't pull out the full state when storing state (#13274) 2022-07-15 12:59:45 +00:00
Erik Johnston
7be954f59b
Fix a bug which could lead to incorrect state (#13278)
There are two fixes here:
1. A long-standing bug where we incorrectly calculated `delta_ids`; and
2. A bug introduced in #13267 where we got current state incorrect.
2022-07-15 11:06:41 +00:00
Erik Johnston
0ca4172b5d
Don't pull out state in compute_event_context for unconflicted state (#13267) 2022-07-14 13:57:02 +00:00
Sean Quah
1391a76cd2
Faster room joins: fix race in recalculation of current room state (#13151)
Bounce recalculation of current state to the correct event persister and
move recalculation of current state into the event persistence queue, to
avoid concurrent updates to a room's current state.

Also give recalculation of a room's current state a real stream
ordering.

Signed-off-by: Sean Quah <seanq@matrix.org>
2022-07-07 12:19:31 +00:00
Sean Quah
68db233f0c
Handle race between persisting an event and un-partial stating a room (#13100)
Whenever we want to persist an event, we first compute an event context,
which includes the state at the event and a flag indicating whether the
state is partial. After a lot of processing, we finally try to store the
event in the database, which can fail for partial state events when the
containing room has been un-partial stated in the meantime.

We detect the race as a foreign key constraint failure in the data store
layer and turn it into a special `PartialStateConflictError` exception,
which makes its way up to the method in which we computed the event
context.

To make things difficult, the exception needs to cross a replication
request: `/fed_send_events` for events coming over federation and
`/send_event` for events from clients. We transport the
`PartialStateConflictError` as a `409 Conflict` over replication and
turn `409`s back into `PartialStateConflictError`s on the worker making
the request.

All client events go through
`EventCreationHandler.handle_new_client_event`, which is called in
*a lot* of places. Instead of trying to update all the code which
creates client events, we turn the `PartialStateConflictError` into a
`429 Too Many Requests` in
`EventCreationHandler.handle_new_client_event` and hope that clients
take it as a hint to retry their request.

On the federation event side, there are 7 places which compute event
contexts. 4 of them use outlier event contexts:
`FederationEventHandler._auth_and_persist_outliers_inner`,
`FederationHandler.do_knock`, `FederationHandler.on_invite_request` and
`FederationHandler.do_remotely_reject_invite`. These events won't have
the partial state flag, so we do not need to do anything for then.

The remaining 3 paths which create events are
`FederationEventHandler.process_remote_join`,
`FederationEventHandler.on_send_membership_event` and
`FederationEventHandler._process_received_pdu`.

We can't experience the race in `process_remote_join`, unless we're
handling an additional join into a partial state room, which currently
blocks, so we make no attempt to handle it correctly.

`on_send_membership_event` is only called by
`FederationServer._on_send_membership_event`, so we catch the
`PartialStateConflictError` there and retry just once.

`_process_received_pdu` is called by `on_receive_pdu` for incoming
events and `_process_pulled_event` for backfill. The latter should never
try to persist partial state events, so we ignore it. We catch the
`PartialStateConflictError` in `on_receive_pdu` and retry just once.

Refering to the graph of code paths in
https://github.com/matrix-org/synapse/issues/12988#issuecomment-1156857648
may make the above make more sense.

Signed-off-by: Sean Quah <seanq@matrix.org>
2022-07-05 16:12:52 +01:00
Richard van der Hoff
7c6b2204d1
Faster joins: add issue links to the TODOs (#13004)
... to help us keep track of these things
2022-06-09 10:13:03 +00:00
Erik Johnston
44de53bb79
Reduce state pulled from DB due to sending typing and receipts over federation (#12964)
Reducing the amount of state we pull from the DB is useful as fetching state is expensive in terms of DB, CPU and memory.
2022-06-06 16:46:11 +01:00
Erik Johnston
e3163e2e11
Reduce the amount of state we pull from the DB (#12811) 2022-06-06 09:24:12 +01:00
Erik Johnston
888a29f412
Wait for lazy join to complete when getting current state (#12872) 2022-06-01 16:02:53 +01:00
Erik Johnston
1e453053cb
Rename storage classes (#12913) 2022-05-31 12:17:50 +00:00