Request partial joins by default (#14905)

* Request partial joins by default

This is a little sloppy, but we are trying to gain confidence in faster
joins in the upcoming RC.

Admins can still opt out by adding the following to their Synapse
config:

```yaml
experimental:
    faster_joins: false
```

We may revert this change before the release proper, depending on how
testing in the wild goes.

* Changelog

* Try to fix the backfill test failures

* Upgrade notes

* Postgres compat?
This commit is contained in:
David Robertson 2023-01-24 15:28:20 +00:00 committed by GitHub
parent 80d44060c9
commit 4607be0b7b
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4 changed files with 49 additions and 7 deletions

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@ -0,0 +1 @@
Faster joins: request partial joins by default. Admins can opt-out of this for the time being---see the upgrade notes.

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@ -90,6 +90,19 @@ process, for example:
# Upgrading to v1.76.0
## Faster joins are enabled by default
When joining a room for the first time, Synapse 1.76.0rc1 will request a partial join from the other server by default. Previously, server admins had to opt-in to this using an experimental config flag.
Server admins can opt out of this feature for the time being by setting
```yaml
experimental:
faster_joins: false
```
in their server config.
## Changes to the account data replication streams
Synapse has changed the format of the account data and devices replication

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@ -84,7 +84,7 @@ class ExperimentalConfig(Config):
# experimental support for faster joins over federation
# (MSC2775, MSC3706, MSC3895)
# requires a target server that can provide a partial join response (MSC3706)
self.faster_joins_enabled: bool = experimental.get("faster_joins", False)
self.faster_joins_enabled: bool = experimental.get("faster_joins", True)
# MSC3720 (Account status endpoint)
self.msc3720_enabled: bool = experimental.get("msc3720_enabled", False)

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@ -67,7 +67,7 @@ from synapse.storage.database import (
make_in_list_sql_clause,
)
from synapse.storage.databases.main.events_worker import EventsWorkerStore
from synapse.storage.engines import BaseDatabaseEngine, PostgresEngine
from synapse.storage.engines import BaseDatabaseEngine, PostgresEngine, Sqlite3Engine
from synapse.storage.util.id_generators import MultiWriterIdGenerator
from synapse.types import PersistedEventPosition, RoomStreamToken
from synapse.util.caches.descriptors import cached
@ -944,12 +944,40 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
room_id
stream_key
"""
sql = (
"SELECT coalesce(MIN(topological_ordering), 0) FROM events"
" WHERE room_id = ? AND stream_ordering >= ?"
)
if isinstance(self.database_engine, PostgresEngine):
min_function = "LEAST"
elif isinstance(self.database_engine, Sqlite3Engine):
min_function = "MIN"
else:
raise RuntimeError(f"Unknown database engine {self.database_engine}")
# This query used to be
# SELECT COALESCE(MIN(topological_ordering), 0) FROM events
# WHERE room_id = ? and events.stream_ordering >= {stream_key}
# which returns 0 if the stream_key is newer than any event in
# the room. That's not wrong, but it seems to interact oddly with backfill,
# requiring a second call to /messages to actually backfill from a remote
# homeserver.
#
# Instead, rollback the stream ordering to that after the most recent event in
# this room.
sql = f"""
WITH fallback(max_stream_ordering) AS (
SELECT MAX(stream_ordering)
FROM events
WHERE room_id = ?
)
SELECT COALESCE(MIN(topological_ordering), 0) FROM events
WHERE
room_id = ?
AND events.stream_ordering >= {min_function}(
?,
(SELECT max_stream_ordering FROM fallback)
)
"""
row = await self.db_pool.execute(
"get_current_topological_token", None, sql, room_id, stream_key
"get_current_topological_token", None, sql, room_id, room_id, stream_key
)
return row[0][0] if row else 0