From 5121f9210c989fcc909e78195133876dff3bc9b9 Mon Sep 17 00:00:00 2001
From: Devon Hudson <devon.dmytro@gmail.com>
Date: Tue, 25 Feb 2025 16:25:39 +0000
Subject: [PATCH] Add background job to clear unreferenced state groups
(#18154)
Fixes #18150
### Pull Request Checklist
<!-- Please read
https://element-hq.github.io/synapse/latest/development/contributing_guide.html
before submitting your pull request -->
* [X] Pull request is based on the develop branch
* [x] Pull request includes a [changelog
file](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#changelog).
The entry should:
- Be a short description of your change which makes sense to users.
"Fixed a bug that prevented receiving messages from other servers."
instead of "Moved X method from `EventStore` to `EventWorkerStore`.".
- Use markdown where necessary, mostly for `code blocks`.
- End with either a period (.) or an exclamation mark (!).
- Start with a capital letter.
- Feel free to credit yourself, by adding a sentence "Contributed by
@github_username." or "Contributed by [Your Name]." to the end of the
entry.
* [X] [Code
style](https://element-hq.github.io/synapse/latest/code_style.html) is
correct
(run the
[linters](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#run-the-linters))
---------
Co-authored-by: Erik Johnston <erikj@element.io>
---
changelog.d/18154.feature | 1 +
docs/development/database_schema.md | 2 +-
synapse/_scripts/synapse_port_db.py | 30 +++
synapse/storage/controllers/purge_events.py | 246 +++++++++++++-----
synapse/storage/databases/state/bg_updates.py | 10 +-
synapse/storage/databases/state/deletion.py | 42 ++-
synapse/storage/schema/__init__.py | 1 +
.../02_delete_unreferenced_state_groups.sql | 16 ++
synapse/types/storage/__init__.py | 4 +
tests/storage/test_purge.py | 97 +++++++
10 files changed, 375 insertions(+), 74 deletions(-)
create mode 100644 changelog.d/18154.feature
create mode 100644 synapse/storage/schema/state/delta/89/02_delete_unreferenced_state_groups.sql
diff --git a/changelog.d/18154.feature b/changelog.d/18154.feature
new file mode 100644
index 0000000000..62e1b79a15
--- /dev/null
+++ b/changelog.d/18154.feature
@@ -0,0 +1 @@
+Add background job to clear unreferenced state groups.
diff --git a/docs/development/database_schema.md b/docs/development/database_schema.md
index 37a06acc12..620d1c16b0 100644
--- a/docs/development/database_schema.md
+++ b/docs/development/database_schema.md
@@ -162,7 +162,7 @@ by a unique name, the current status (stored in JSON), and some dependency infor
* Whether the update requires a previous update to be complete.
* A rough ordering for which to complete updates.
-A new background updates needs to be added to the `background_updates` table:
+A new background update needs to be added to the `background_updates` table:
```sql
INSERT INTO background_updates (ordering, update_name, depends_on, progress_json) VALUES
diff --git a/synapse/_scripts/synapse_port_db.py b/synapse/_scripts/synapse_port_db.py
index 3f67a739a0..59065a0504 100755
--- a/synapse/_scripts/synapse_port_db.py
+++ b/synapse/_scripts/synapse_port_db.py
@@ -191,6 +191,11 @@ APPEND_ONLY_TABLES = [
IGNORED_TABLES = {
+ # Porting the auto generated sequence in this table is non-trivial.
+ # None of the entries in this list are mandatory for Synapse to keep working.
+ # If state group disk space is an issue after the port, the
+ # `delete_unreferenced_state_groups_bg_update` background task can be run again.
+ "state_groups_pending_deletion",
# We don't port these tables, as they're a faff and we can regenerate
# them anyway.
"user_directory",
@@ -216,6 +221,15 @@ IGNORED_TABLES = {
}
+# These background updates will not be applied upon creation of the postgres database.
+IGNORED_BACKGROUND_UPDATES = {
+ # Reapplying this background update to the postgres database is unnecessary after
+ # already having waited for the SQLite database to complete all running background
+ # updates.
+ "delete_unreferenced_state_groups_bg_update",
+}
+
+
# Error returned by the run function. Used at the top-level part of the script to
# handle errors and return codes.
end_error: Optional[str] = None
@@ -687,6 +701,20 @@ class Porter:
# 0 means off. 1 means full. 2 means incremental.
return autovacuum_setting != 0
+ async def remove_ignored_background_updates_from_database(self) -> None:
+ def _remove_delete_unreferenced_state_groups_bg_updates(
+ txn: LoggingTransaction,
+ ) -> None:
+ txn.execute(
+ "DELETE FROM background_updates WHERE update_name = ANY(?)",
+ (list(IGNORED_BACKGROUND_UPDATES),),
+ )
+
+ await self.postgres_store.db_pool.runInteraction(
+ "remove_delete_unreferenced_state_groups_bg_updates",
+ _remove_delete_unreferenced_state_groups_bg_updates,
+ )
+
async def run(self) -> None:
"""Ports the SQLite database to a PostgreSQL database.
@@ -732,6 +760,8 @@ class Porter:
self.hs_config.database.get_single_database()
)
+ await self.remove_ignored_background_updates_from_database()
+
await self.run_background_updates_on_postgres()
self.progress.set_state("Creating port tables")
diff --git a/synapse/storage/controllers/purge_events.py b/synapse/storage/controllers/purge_events.py
index 47cec8c469..ef30bf2895 100644
--- a/synapse/storage/controllers/purge_events.py
+++ b/synapse/storage/controllers/purge_events.py
@@ -21,11 +21,18 @@
import itertools
import logging
-from typing import TYPE_CHECKING, Collection, Mapping, Set
+from typing import (
+ TYPE_CHECKING,
+ Collection,
+ Mapping,
+ Set,
+)
from synapse.logging.context import nested_logging_context
from synapse.metrics.background_process_metrics import wrap_as_background_process
+from synapse.storage.database import LoggingTransaction
from synapse.storage.databases import Databases
+from synapse.types.storage import _BackgroundUpdates
if TYPE_CHECKING:
from synapse.server import HomeServer
@@ -44,6 +51,11 @@ class PurgeEventsStorageController:
self._delete_state_groups_loop, 60 * 1000
)
+ self.stores.state.db_pool.updates.register_background_update_handler(
+ _BackgroundUpdates.DELETE_UNREFERENCED_STATE_GROUPS_BG_UPDATE,
+ self._background_delete_unrefereneced_state_groups,
+ )
+
async def purge_room(self, room_id: str) -> None:
"""Deletes all record of a room"""
@@ -80,68 +92,6 @@ class PurgeEventsStorageController:
sg_to_delete
)
- async def _find_unreferenced_groups(
- self, state_groups: Collection[int]
- ) -> Set[int]:
- """Used when purging history to figure out which state groups can be
- deleted.
-
- Args:
- state_groups: Set of state groups referenced by events
- that are going to be deleted.
-
- Returns:
- The set of state groups that can be deleted.
- """
- # Set of events that we have found to be referenced by events
- referenced_groups = set()
-
- # Set of state groups we've already seen
- state_groups_seen = set(state_groups)
-
- # Set of state groups to handle next.
- next_to_search = set(state_groups)
- while next_to_search:
- # We bound size of groups we're looking up at once, to stop the
- # SQL query getting too big
- if len(next_to_search) < 100:
- current_search = next_to_search
- next_to_search = set()
- else:
- current_search = set(itertools.islice(next_to_search, 100))
- next_to_search -= current_search
-
- referenced = await self.stores.main.get_referenced_state_groups(
- current_search
- )
- referenced_groups |= referenced
-
- # We don't continue iterating up the state group graphs for state
- # groups that are referenced.
- current_search -= referenced
-
- edges = await self.stores.state.get_previous_state_groups(current_search)
-
- prevs = set(edges.values())
- # We don't bother re-handling groups we've already seen
- prevs -= state_groups_seen
- next_to_search |= prevs
- state_groups_seen |= prevs
-
- # We also check to see if anything referencing the state groups are
- # also unreferenced. This helps ensure that we delete unreferenced
- # state groups, if we don't then we will de-delta them when we
- # delete the other state groups leading to increased DB usage.
- next_edges = await self.stores.state.get_next_state_groups(current_search)
- nexts = set(next_edges.keys())
- nexts -= state_groups_seen
- next_to_search |= nexts
- state_groups_seen |= nexts
-
- to_delete = state_groups_seen - referenced_groups
-
- return to_delete
-
@wrap_as_background_process("_delete_state_groups_loop")
async def _delete_state_groups_loop(self) -> None:
"""Background task that deletes any state groups that may be pending
@@ -203,3 +153,173 @@ class PurgeEventsStorageController:
room_id,
groups_to_sequences,
)
+
+ async def _background_delete_unrefereneced_state_groups(
+ self, progress: dict, batch_size: int
+ ) -> int:
+ """This background update will slowly delete any unreferenced state groups"""
+
+ last_checked_state_group = progress.get("last_checked_state_group")
+ max_state_group = progress.get("max_state_group")
+
+ if last_checked_state_group is None or max_state_group is None:
+ # This is the first run.
+ last_checked_state_group = 0
+
+ max_state_group = await self.stores.state.db_pool.simple_select_one_onecol(
+ table="state_groups",
+ keyvalues={},
+ retcol="MAX(id)",
+ allow_none=True,
+ desc="get_max_state_group",
+ )
+ if max_state_group is None:
+ # There are no state groups so the background process is finished.
+ await self.stores.state.db_pool.updates._end_background_update(
+ _BackgroundUpdates.DELETE_UNREFERENCED_STATE_GROUPS_BG_UPDATE
+ )
+ return batch_size
+
+ (
+ last_checked_state_group,
+ final_batch,
+ ) = await self._delete_unreferenced_state_groups_batch(
+ last_checked_state_group, batch_size, max_state_group
+ )
+
+ if not final_batch:
+ # There are more state groups to check.
+ progress = {
+ "last_checked_state_group": last_checked_state_group,
+ "max_state_group": max_state_group,
+ }
+ await self.stores.state.db_pool.updates._background_update_progress(
+ _BackgroundUpdates.DELETE_UNREFERENCED_STATE_GROUPS_BG_UPDATE,
+ progress,
+ )
+ else:
+ # This background process is finished.
+ await self.stores.state.db_pool.updates._end_background_update(
+ _BackgroundUpdates.DELETE_UNREFERENCED_STATE_GROUPS_BG_UPDATE
+ )
+
+ return batch_size
+
+ async def _delete_unreferenced_state_groups_batch(
+ self,
+ last_checked_state_group: int,
+ batch_size: int,
+ max_state_group: int,
+ ) -> tuple[int, bool]:
+ """Looks for unreferenced state groups starting from the last state group
+ checked, and any state groups which would become unreferenced if a state group
+ was deleted, and marks them for deletion.
+
+ Args:
+ last_checked_state_group: The last state group that was checked.
+ batch_size: How many state groups to process in this iteration.
+
+ Returns:
+ (last_checked_state_group, final_batch)
+ """
+
+ # Look for state groups that can be cleaned up.
+ def get_next_state_groups_txn(txn: LoggingTransaction) -> Set[int]:
+ state_group_sql = "SELECT id FROM state_groups WHERE ? < id AND id <= ? ORDER BY id LIMIT ?"
+ txn.execute(
+ state_group_sql, (last_checked_state_group, max_state_group, batch_size)
+ )
+
+ next_set = {row[0] for row in txn}
+
+ return next_set
+
+ next_set = await self.stores.state.db_pool.runInteraction(
+ "get_next_state_groups", get_next_state_groups_txn
+ )
+
+ final_batch = False
+ if len(next_set) < batch_size:
+ final_batch = True
+ else:
+ last_checked_state_group = max(next_set)
+
+ if len(next_set) == 0:
+ return last_checked_state_group, final_batch
+
+ # Find all state groups that can be deleted if the original set is deleted.
+ # This set includes the original set, as well as any state groups that would
+ # become unreferenced upon deleting the original set.
+ to_delete = await self._find_unreferenced_groups(next_set)
+
+ if len(to_delete) == 0:
+ return last_checked_state_group, final_batch
+
+ await self.stores.state_deletion.mark_state_groups_as_pending_deletion(
+ to_delete
+ )
+
+ return last_checked_state_group, final_batch
+
+ async def _find_unreferenced_groups(
+ self,
+ state_groups: Collection[int],
+ ) -> Set[int]:
+ """Used when purging history to figure out which state groups can be
+ deleted.
+
+ Args:
+ state_groups: Set of state groups referenced by events
+ that are going to be deleted.
+
+ Returns:
+ The set of state groups that can be deleted.
+ """
+ # Set of events that we have found to be referenced by events
+ referenced_groups = set()
+
+ # Set of state groups we've already seen
+ state_groups_seen = set(state_groups)
+
+ # Set of state groups to handle next.
+ next_to_search = set(state_groups)
+ while next_to_search:
+ # We bound size of groups we're looking up at once, to stop the
+ # SQL query getting too big
+ if len(next_to_search) < 100:
+ current_search = next_to_search
+ next_to_search = set()
+ else:
+ current_search = set(itertools.islice(next_to_search, 100))
+ next_to_search -= current_search
+
+ referenced = await self.stores.main.get_referenced_state_groups(
+ current_search
+ )
+ referenced_groups |= referenced
+
+ # We don't continue iterating up the state group graphs for state
+ # groups that are referenced.
+ current_search -= referenced
+
+ edges = await self.stores.state.get_previous_state_groups(current_search)
+
+ prevs = set(edges.values())
+ # We don't bother re-handling groups we've already seen
+ prevs -= state_groups_seen
+ next_to_search |= prevs
+ state_groups_seen |= prevs
+
+ # We also check to see if anything referencing the state groups are
+ # also unreferenced. This helps ensure that we delete unreferenced
+ # state groups, if we don't then we will de-delta them when we
+ # delete the other state groups leading to increased DB usage.
+ next_edges = await self.stores.state.get_next_state_groups(current_search)
+ nexts = set(next_edges.keys())
+ nexts -= state_groups_seen
+ next_to_search |= nexts
+ state_groups_seen |= nexts
+
+ to_delete = state_groups_seen - referenced_groups
+
+ return to_delete
diff --git a/synapse/storage/databases/state/bg_updates.py b/synapse/storage/databases/state/bg_updates.py
index f7824cba0f..95fd0ae73a 100644
--- a/synapse/storage/databases/state/bg_updates.py
+++ b/synapse/storage/databases/state/bg_updates.py
@@ -20,7 +20,15 @@
#
import logging
-from typing import TYPE_CHECKING, Dict, List, Mapping, Optional, Tuple, Union
+from typing import (
+ TYPE_CHECKING,
+ Dict,
+ List,
+ Mapping,
+ Optional,
+ Tuple,
+ Union,
+)
from synapse.logging.opentracing import tag_args, trace
from synapse.storage._base import SQLBaseStore
diff --git a/synapse/storage/databases/state/deletion.py b/synapse/storage/databases/state/deletion.py
index d4b1c20a45..f77c46f6ae 100644
--- a/synapse/storage/databases/state/deletion.py
+++ b/synapse/storage/databases/state/deletion.py
@@ -321,19 +321,43 @@ class StateDeletionDataStore:
async def mark_state_groups_as_pending_deletion(
self, state_groups: Collection[int]
) -> None:
- """Mark the given state groups as pending deletion"""
+ """Mark the given state groups as pending deletion.
- now = self._clock.time_msec()
+ If any of the state groups are already pending deletion, then those records are
+ left as is.
+ """
- await self.db_pool.simple_upsert_many(
- table="state_groups_pending_deletion",
- key_names=("state_group",),
- key_values=[(state_group,) for state_group in state_groups],
- value_names=("insertion_ts",),
- value_values=[(now,) for _ in state_groups],
- desc="mark_state_groups_as_pending_deletion",
+ await self.db_pool.runInteraction(
+ "mark_state_groups_as_pending_deletion",
+ self._mark_state_groups_as_pending_deletion_txn,
+ state_groups,
)
+ def _mark_state_groups_as_pending_deletion_txn(
+ self,
+ txn: LoggingTransaction,
+ state_groups: Collection[int],
+ ) -> None:
+ sql = """
+ INSERT INTO state_groups_pending_deletion (state_group, insertion_ts)
+ VALUES %s
+ ON CONFLICT (state_group)
+ DO NOTHING
+ """
+
+ now = self._clock.time_msec()
+ rows = [
+ (
+ state_group,
+ now,
+ )
+ for state_group in state_groups
+ ]
+ if isinstance(txn.database_engine, PostgresEngine):
+ txn.execute_values(sql % ("?",), rows, fetch=False)
+ else:
+ txn.execute_batch(sql % ("(?, ?)",), rows)
+
async def mark_state_groups_as_used(self, state_groups: Collection[int]) -> None:
"""Mark the given state groups as now being referenced"""
diff --git a/synapse/storage/schema/__init__.py b/synapse/storage/schema/__init__.py
index 49e648a92f..c90c2c6051 100644
--- a/synapse/storage/schema/__init__.py
+++ b/synapse/storage/schema/__init__.py
@@ -158,6 +158,7 @@ Changes in SCHEMA_VERSION = 88
Changes in SCHEMA_VERSION = 89
- Add `state_groups_pending_deletion` and `state_groups_persisting` tables.
+ - Add background update to delete unreferenced state groups.
"""
diff --git a/synapse/storage/schema/state/delta/89/02_delete_unreferenced_state_groups.sql b/synapse/storage/schema/state/delta/89/02_delete_unreferenced_state_groups.sql
new file mode 100644
index 0000000000..184dc8564c
--- /dev/null
+++ b/synapse/storage/schema/state/delta/89/02_delete_unreferenced_state_groups.sql
@@ -0,0 +1,16 @@
+--
+-- This file is licensed under the Affero General Public License (AGPL) version 3.
+--
+-- Copyright (C) 2025 New Vector, Ltd
+--
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero General Public License as
+-- published by the Free Software Foundation, either version 3 of the
+-- License, or (at your option) any later version.
+--
+-- See the GNU Affero General Public License for more details:
+-- <https://www.gnu.org/licenses/agpl-3.0.html>.
+
+-- Add a background update to delete any unreferenced state groups
+INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
+ (8902, 'delete_unreferenced_state_groups_bg_update', '{}');
diff --git a/synapse/types/storage/__init__.py b/synapse/types/storage/__init__.py
index b5fa20a41a..d0a85ef208 100644
--- a/synapse/types/storage/__init__.py
+++ b/synapse/types/storage/__init__.py
@@ -48,3 +48,7 @@ class _BackgroundUpdates:
SLIDING_SYNC_MEMBERSHIP_SNAPSHOTS_FIX_FORGOTTEN_COLUMN_BG_UPDATE = (
"sliding_sync_membership_snapshots_fix_forgotten_column_bg_update"
)
+
+ DELETE_UNREFERENCED_STATE_GROUPS_BG_UPDATE = (
+ "delete_unreferenced_state_groups_bg_update"
+ )
diff --git a/tests/storage/test_purge.py b/tests/storage/test_purge.py
index 916e42e731..ecdc893405 100644
--- a/tests/storage/test_purge.py
+++ b/tests/storage/test_purge.py
@@ -24,6 +24,7 @@ from synapse.api.errors import NotFoundError, SynapseError
from synapse.rest.client import room
from synapse.server import HomeServer
from synapse.types.state import StateFilter
+from synapse.types.storage import _BackgroundUpdates
from synapse.util import Clock
from tests.unittest import HomeserverTestCase
@@ -303,3 +304,99 @@ class PurgeTests(HomeserverTestCase):
)
)
self.assertEqual(len(state_groups), 1)
+
+ def test_clear_unreferenced_state_groups(self) -> None:
+ """Test that any unreferenced state groups are automatically cleaned up."""
+
+ self.helper.send(self.room_id, body="test1")
+ state1 = self.helper.send_state(
+ self.room_id, "org.matrix.test", body={"number": 2}
+ )
+ # Create enough state events to require multiple batches of
+ # delete_unreferenced_state_groups_bg_update to be run.
+ for i in range(200):
+ self.helper.send_state(self.room_id, "org.matrix.test", body={"number": i})
+ state2 = self.helper.send_state(
+ self.room_id, "org.matrix.test", body={"number": 3}
+ )
+ self.helper.send(self.room_id, body="test4")
+ last = self.helper.send(self.room_id, body="test5")
+
+ # Create an unreferenced state group that has a prev group of one of the
+ # to-be-purged events.
+ prev_group = self.get_success(
+ self.store._get_state_group_for_event(state1["event_id"])
+ )
+ unreferenced_state_group = self.get_success(
+ self.state_store.store_state_group(
+ event_id=last["event_id"],
+ room_id=self.room_id,
+ prev_group=prev_group,
+ delta_ids={("org.matrix.test", ""): state2["event_id"]},
+ current_state_ids=None,
+ )
+ )
+
+ another_unreferenced_state_group = self.get_success(
+ self.state_store.store_state_group(
+ event_id=last["event_id"],
+ room_id=self.room_id,
+ prev_group=unreferenced_state_group,
+ delta_ids={("org.matrix.test", ""): state2["event_id"]},
+ current_state_ids=None,
+ )
+ )
+
+ # Insert and run the background update.
+ self.get_success(
+ self.store.db_pool.simple_insert(
+ "background_updates",
+ {
+ "update_name": _BackgroundUpdates.DELETE_UNREFERENCED_STATE_GROUPS_BG_UPDATE,
+ "progress_json": "{}",
+ },
+ )
+ )
+ self.store.db_pool.updates._all_done = False
+ self.wait_for_background_updates()
+
+ # Advance so that the background job to delete the state groups runs
+ self.reactor.advance(
+ 1 + self.state_deletion_store.DELAY_BEFORE_DELETION_MS / 1000
+ )
+
+ # We expect that the unreferenced state group has been deleted.
+ row = self.get_success(
+ self.state_store.db_pool.simple_select_one_onecol(
+ table="state_groups",
+ keyvalues={"id": unreferenced_state_group},
+ retcol="id",
+ allow_none=True,
+ desc="test_purge_unreferenced_state_group",
+ )
+ )
+ self.assertIsNone(row)
+
+ # We expect that the other unreferenced state group has also been deleted.
+ row = self.get_success(
+ self.state_store.db_pool.simple_select_one_onecol(
+ table="state_groups",
+ keyvalues={"id": another_unreferenced_state_group},
+ retcol="id",
+ allow_none=True,
+ desc="test_purge_unreferenced_state_group",
+ )
+ )
+ self.assertIsNone(row)
+
+ # We expect there to now only be one state group for the room, which is
+ # the state group of the last event (as the only outlier).
+ state_groups = self.get_success(
+ self.state_store.db_pool.simple_select_onecol(
+ table="state_groups",
+ keyvalues={"room_id": self.room_id},
+ retcol="id",
+ desc="test_purge_unreferenced_state_group",
+ )
+ )
+ self.assertEqual(len(state_groups), 207)
--
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