diff --git a/synapse/storage/controllers/purge_events.py b/synapse/storage/controllers/purge_events.py
index 47cec8c469..c2d4bf8290 100644
--- a/synapse/storage/controllers/purge_events.py
+++ b/synapse/storage/controllers/purge_events.py
@@ -21,11 +21,19 @@
import itertools
import logging
-from typing import TYPE_CHECKING, Collection, Mapping, Set
+from typing import (
+ TYPE_CHECKING,
+ Collection,
+ Mapping,
+ Optional,
+ 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 +52,11 @@ class PurgeEventsStorageController:
self._delete_state_groups_loop, 60 * 1000
)
+ self.stores.state.db_pool.updates.register_background_update_handler(
+ _BackgroundUpdates.MARK_UNREFERENCED_STATE_GROUPS_FOR_DELETION_BG_UPDATE,
+ self._background_delete_unrefereneced_state_groups,
+ )
+
async def purge_room(self, room_id: str) -> None:
"""Deletes all record of a room"""
@@ -81,7 +94,8 @@ class PurgeEventsStorageController:
)
async def _find_unreferenced_groups(
- self, state_groups: Collection[int]
+ self,
+ state_groups: Collection[int],
) -> Set[int]:
"""Used when purging history to figure out which state groups can be
deleted.
@@ -203,3 +217,232 @@ 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")
+
+ if last_checked_state_group is None:
+ # This is the first run.
+ last_checked_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 last_checked_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.MARK_UNREFERENCED_STATE_GROUPS_FOR_DELETION_BG_UPDATE
+ )
+ return batch_size
+ last_checked_state_group += 1
+
+ (
+ last_checked_state_group,
+ final_batch,
+ ) = await self._delete_unreferenced_state_groups_batch(
+ last_checked_state_group,
+ batch_size,
+ )
+
+ if not final_batch:
+ # There are more state groups to check.
+ progress = {
+ "last_checked_state_group": last_checked_state_group,
+ }
+ await self.stores.state.db_pool.updates._background_update_progress(
+ _BackgroundUpdates.MARK_UNREFERENCED_STATE_GROUPS_FOR_DELETION_BG_UPDATE,
+ progress,
+ )
+ else:
+ # This background process is finished.
+ await self.stores.state.db_pool.updates._end_background_update(
+ _BackgroundUpdates.MARK_UNREFERENCED_STATE_GROUPS_FOR_DELETION_BG_UPDATE
+ )
+
+ return batch_size
+
+ async def _delete_unreferenced_state_groups_batch(
+ self,
+ last_checked_state_group: int,
+ batch_size: int,
+ ) -> tuple[int, bool]:
+ """Looks for unreferenced state groups starting from the last state group
+ checked 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)
+ """
+
+ # Find all state groups that can be deleted if any of the original set are deleted.
+ (
+ to_delete,
+ last_checked_state_group,
+ final_batch,
+ ) = await self._find_unreferenced_groups_for_background_deletion(
+ last_checked_state_group, batch_size
+ )
+
+ 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_for_background_deletion(
+ self,
+ last_checked_state_group: int,
+ batch_size: int,
+ ) -> tuple[Set[int], int, bool]:
+ """Used when deleting unreferenced state groups in the background to figure out
+ which state groups can be deleted.
+ To avoid increased DB usage due to de-deltaing state groups, this returns only
+ state groups which are free standing (ie. no shared edges with referenced groups) or
+ state groups which do not share edges which result in a future referenced group.
+
+ The following scenarios outline the possibilities based on state group data in
+ the DB.
+
+ ie. Free standing -> state groups 1-N would be returned:
+ SG_1
+ |
+ ...
+ |
+ SG_N
+
+ ie. Previous reference -> state groups 2-N would be returned:
+ SG_1 <- referenced by event
+ |
+ SG_2
+ |
+ ...
+ |
+ SG_N
+
+ ie. Future reference -> none of the following state groups would be returned:
+ SG_1
+ |
+ SG_2
+ |
+ ...
+ |
+ SG_N <- referenced by event
+
+ Args:
+ last_checked_state_group: The last state group that was checked.
+ batch_size: How many state groups to process in this iteration.
+
+ Returns:
+ (to_delete, last_checked_state_group, final_batch)
+ """
+
+ # If a state group's next edge is not pending deletion then we don't delete the state group.
+ # If there is no next edge or the next edges are all marked for deletion, then delete
+ # the state group.
+ # This holds since we walk backwards from the latest state groups, ensuring that
+ # we've already checked newer state groups for event references along the way.
+ def get_next_state_groups_marked_for_deletion_txn(
+ txn: LoggingTransaction,
+ ) -> tuple[dict[int, bool], dict[int, int]]:
+ state_group_sql = """
+ SELECT s.id, e.state_group, d.state_group
+ FROM (
+ SELECT id FROM state_groups
+ WHERE id < ? ORDER BY id DESC LIMIT ?
+ ) as s
+ LEFT JOIN state_group_edges AS e ON (s.id = e.prev_state_group)
+ LEFT JOIN state_groups_pending_deletion AS d ON (e.state_group = d.state_group)
+ """
+ txn.execute(state_group_sql, (last_checked_state_group, batch_size))
+
+ # Mapping from state group to whether we should delete it.
+ state_groups_to_deletion: dict[int, bool] = {}
+
+ # Mapping from state group to prev state group.
+ state_groups_to_prev: dict[int, int] = {}
+
+ for row in txn:
+ state_group = row[0]
+ next_edge = row[1]
+ pending_deletion = row[2]
+
+ if next_edge is not None:
+ state_groups_to_prev[next_edge] = state_group
+
+ if next_edge is not None and not pending_deletion:
+ # We have found an edge not marked for deletion.
+ # Check previous results to see if this group is part of a chain
+ # within this batch that qualifies for deletion.
+ # ie. batch contains:
+ # SG_1 -> SG_2 -> SG_3
+ # If SG_3 is a candidate for deletion, then SG_2 & SG_1 should also
+ # be, even though they have edges which may not be marked for
+ # deletion.
+ # This relies on SQL results being sorted in DESC order to work.
+ next_is_deletion_candidate = state_groups_to_deletion.get(next_edge)
+ if (
+ next_is_deletion_candidate is None
+ or not next_is_deletion_candidate
+ ):
+ state_groups_to_deletion[state_group] = False
+ else:
+ state_groups_to_deletion.setdefault(state_group, True)
+ else:
+ # This state group may be a candidate for deletion
+ state_groups_to_deletion.setdefault(state_group, True)
+
+ return state_groups_to_deletion, state_groups_to_prev
+
+ (
+ state_groups_to_deletion,
+ state_group_edges,
+ ) = await self.stores.state.db_pool.runInteraction(
+ "get_next_state_groups_marked_for_deletion",
+ get_next_state_groups_marked_for_deletion_txn,
+ )
+ deletion_candidates = {
+ state_group
+ for state_group, deletion in state_groups_to_deletion.items()
+ if deletion
+ }
+
+ final_batch = False
+ state_groups = state_groups_to_deletion.keys()
+ if len(state_groups) < batch_size:
+ final_batch = True
+ else:
+ last_checked_state_group = min(state_groups)
+
+ if len(state_groups) == 0:
+ return set(), last_checked_state_group, final_batch
+
+ # Determine if any of the remaining state groups are directly referenced.
+ referenced = await self.stores.main.get_referenced_state_groups(
+ deletion_candidates
+ )
+
+ # Remove state groups from deletion_candidates which are directly referenced or share a
+ # future edge with a referenced state group within this batch.
+ def filter_reference_chains(group: Optional[int]) -> None:
+ while group is not None:
+ deletion_candidates.discard(group)
+ group = state_group_edges.get(group)
+
+ for referenced_group in referenced:
+ filter_reference_chains(referenced_group)
+
+ return deletion_candidates, last_checked_state_group, final_batch
|
