502 lines
18 KiB
Python
502 lines
18 KiB
Python
# Copyright 2020 The Matrix.org Foundation C.I.C.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import logging
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from typing import Any, List, Set, Tuple, cast
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from synapse.api.errors import SynapseError
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from synapse.storage.database import LoggingTransaction
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from synapse.storage.databases.main import CacheInvalidationWorkerStore
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from synapse.storage.databases.main.state import StateGroupWorkerStore
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from synapse.storage.engines import PostgresEngine
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from synapse.storage.engines._base import IsolationLevel
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from synapse.types import RoomStreamToken
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logger = logging.getLogger(__name__)
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class PurgeEventsStore(StateGroupWorkerStore, CacheInvalidationWorkerStore):
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async def purge_history(
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self, room_id: str, token: str, delete_local_events: bool
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) -> Set[int]:
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"""Deletes room history before a certain point.
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Note that only a single purge can occur at once, this is guaranteed via
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a higher level (in the PaginationHandler).
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Args:
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room_id:
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token: A topological token to delete events before
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delete_local_events:
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if True, we will delete local events as well as remote ones
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(instead of just marking them as outliers and deleting their
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state groups).
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Returns:
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The set of state groups that are referenced by deleted events.
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"""
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parsed_token = await RoomStreamToken.parse(self, token)
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return await self.db_pool.runInteraction(
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"purge_history",
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self._purge_history_txn,
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room_id,
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parsed_token,
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delete_local_events,
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)
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def _purge_history_txn(
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self,
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txn: LoggingTransaction,
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room_id: str,
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token: RoomStreamToken,
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delete_local_events: bool,
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) -> Set[int]:
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# Tables that should be pruned:
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# event_auth
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# event_backward_extremities
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# event_edges
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# event_forward_extremities
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# event_json
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# event_push_actions
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# event_relations
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# event_search
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# event_to_state_groups
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# events
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# rejections
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# room_depth
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# state_groups
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# state_groups_state
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# destination_rooms
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# we will build a temporary table listing the events so that we don't
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# have to keep shovelling the list back and forth across the
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# connection. Annoyingly the python sqlite driver commits the
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# transaction on CREATE, so let's do this first.
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#
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# furthermore, we might already have the table from a previous (failed)
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# purge attempt, so let's drop the table first.
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if isinstance(self.database_engine, PostgresEngine):
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# Disable statement timeouts for this transaction; purging rooms can
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# take a while!
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txn.execute("SET LOCAL statement_timeout = 0")
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txn.execute("DROP TABLE IF EXISTS events_to_purge")
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txn.execute(
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"CREATE TEMPORARY TABLE events_to_purge ("
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" event_id TEXT NOT NULL,"
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" should_delete BOOLEAN NOT NULL"
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")"
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)
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# First ensure that we're not about to delete all the forward extremeties
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txn.execute(
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"SELECT e.event_id, e.depth FROM events as e "
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"INNER JOIN event_forward_extremities as f "
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"ON e.event_id = f.event_id "
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"AND e.room_id = f.room_id "
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"WHERE f.room_id = ?",
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(room_id,),
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)
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rows = txn.fetchall()
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# if we already have no forwards extremities (for example because they were
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# cleared out by the `delete_old_current_state_events` background database
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# update), then we may as well carry on.
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if rows:
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max_depth = max(row[1] for row in rows)
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if max_depth < token.topological:
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# We need to ensure we don't delete all the events from the database
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# otherwise we wouldn't be able to send any events (due to not
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# having any backwards extremities)
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raise SynapseError(
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400, "topological_ordering is greater than forward extremities"
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)
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logger.info("[purge] looking for events to delete")
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should_delete_expr = "state_events.state_key IS NULL"
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should_delete_params: Tuple[Any, ...] = ()
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if not delete_local_events:
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should_delete_expr += " AND event_id NOT LIKE ?"
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# We include the parameter twice since we use the expression twice
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should_delete_params += ("%:" + self.hs.hostname, "%:" + self.hs.hostname)
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should_delete_params += (room_id, token.topological)
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# Note that we insert events that are outliers and aren't going to be
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# deleted, as nothing will happen to them.
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txn.execute(
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"INSERT INTO events_to_purge"
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" SELECT event_id, %s"
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" FROM events AS e LEFT JOIN state_events USING (event_id)"
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" WHERE (NOT outlier OR (%s)) AND e.room_id = ? AND topological_ordering < ?"
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% (should_delete_expr, should_delete_expr),
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should_delete_params,
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)
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# We create the indices *after* insertion as that's a lot faster.
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# create an index on should_delete because later we'll be looking for
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# the should_delete / shouldn't_delete subsets
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txn.execute(
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"CREATE INDEX events_to_purge_should_delete"
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" ON events_to_purge(should_delete)"
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)
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# We do joins against events_to_purge for e.g. calculating state
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# groups to purge, etc., so lets make an index.
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txn.execute("CREATE INDEX events_to_purge_id ON events_to_purge(event_id)")
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txn.execute("SELECT event_id, should_delete FROM events_to_purge")
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event_rows = txn.fetchall()
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logger.info(
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"[purge] found %i events before cutoff, of which %i can be deleted",
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len(event_rows),
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sum(1 for e in event_rows if e[1]),
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)
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logger.info("[purge] Finding new backward extremities")
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# We calculate the new entries for the backward extremities by finding
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# events to be purged that are pointed to by events we're not going to
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# purge.
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txn.execute(
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"SELECT DISTINCT e.event_id FROM events_to_purge AS e"
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" INNER JOIN event_edges AS ed ON e.event_id = ed.prev_event_id"
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" LEFT JOIN events_to_purge AS ep2 ON ed.event_id = ep2.event_id"
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" WHERE ep2.event_id IS NULL"
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)
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new_backwards_extrems = txn.fetchall()
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logger.info("[purge] replacing backward extremities: %r", new_backwards_extrems)
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txn.execute(
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"DELETE FROM event_backward_extremities WHERE room_id = ?", (room_id,)
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)
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# Update backward extremeties
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txn.execute_batch(
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"INSERT INTO event_backward_extremities (room_id, event_id)"
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" VALUES (?, ?)",
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[(room_id, event_id) for event_id, in new_backwards_extrems],
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)
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logger.info("[purge] finding state groups referenced by deleted events")
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# Get all state groups that are referenced by events that are to be
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# deleted.
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txn.execute(
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"""
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SELECT DISTINCT state_group FROM events_to_purge
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INNER JOIN event_to_state_groups USING (event_id)
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"""
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)
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referenced_state_groups = {sg for sg, in txn}
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logger.info(
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"[purge] found %i referenced state groups", len(referenced_state_groups)
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)
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logger.info("[purge] removing events from event_to_state_groups")
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txn.execute(
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"DELETE FROM event_to_state_groups "
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"WHERE event_id IN (SELECT event_id from events_to_purge)"
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)
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# Delete all remote non-state events
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for table in (
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"event_edges",
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"events",
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"event_json",
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"event_auth",
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"event_forward_extremities",
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"event_relations",
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"event_search",
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"rejections",
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"redactions",
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):
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logger.info("[purge] removing events from %s", table)
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txn.execute(
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"DELETE FROM %s WHERE event_id IN ("
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" SELECT event_id FROM events_to_purge WHERE should_delete"
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")" % (table,)
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)
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# event_push_actions lacks an index on event_id, and has one on
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# (room_id, event_id) instead.
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for table in ("event_push_actions",):
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logger.info("[purge] removing events from %s", table)
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txn.execute(
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"DELETE FROM %s WHERE room_id = ? AND event_id IN ("
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" SELECT event_id FROM events_to_purge WHERE should_delete"
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")" % (table,),
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(room_id,),
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)
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# Mark all state and own events as outliers
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logger.info("[purge] marking remaining events as outliers")
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txn.execute(
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"UPDATE events SET outlier = TRUE"
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" WHERE event_id IN ("
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" SELECT event_id FROM events_to_purge "
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" WHERE NOT should_delete"
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")"
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)
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# synapse tries to take out an exclusive lock on room_depth whenever it
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# persists events (because upsert), and once we run this update, we
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# will block that for the rest of our transaction.
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#
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# So, let's stick it at the end so that we don't block event
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# persistence.
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#
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# We do this by calculating the minimum depth of the backwards
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# extremities. However, the events in event_backward_extremities
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# are ones we don't have yet so we need to look at the events that
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# point to it via event_edges table.
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txn.execute(
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"""
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SELECT COALESCE(MIN(depth), 0)
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FROM event_backward_extremities AS eb
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INNER JOIN event_edges AS eg ON eg.prev_event_id = eb.event_id
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INNER JOIN events AS e ON e.event_id = eg.event_id
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WHERE eb.room_id = ?
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""",
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(room_id,),
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)
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(min_depth,) = cast(Tuple[int], txn.fetchone())
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logger.info("[purge] updating room_depth to %d", min_depth)
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txn.execute(
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"UPDATE room_depth SET min_depth = ? WHERE room_id = ?",
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(min_depth, room_id),
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)
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# finally, drop the temp table. this will commit the txn in sqlite,
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# so make sure to keep this actually last.
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txn.execute("DROP TABLE events_to_purge")
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self._invalidate_cache_and_stream_bulk(
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txn,
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self._get_state_group_for_event,
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[(event_id,) for event_id, _ in event_rows],
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)
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# XXX: This is racy, since have_seen_events could be called between the
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# transaction completing and the invalidation running. On the other hand,
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# that's no different to calling `have_seen_events` just before the
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# event is deleted from the database.
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self._invalidate_cache_and_stream_bulk(
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txn,
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self.have_seen_event,
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[
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(room_id, event_id)
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for event_id, should_delete in event_rows
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if should_delete
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],
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)
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for event_id, should_delete in event_rows:
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if should_delete:
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self.invalidate_get_event_cache_after_txn(txn, event_id)
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logger.info("[purge] done")
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self._invalidate_caches_for_room_events_and_stream(txn, room_id)
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return referenced_state_groups
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async def purge_room(self, room_id: str) -> List[int]:
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"""Deletes all record of a room
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Args:
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room_id
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Returns:
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The list of state groups to delete.
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"""
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# This first runs the purge transaction with READ_COMMITTED isolation level,
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# meaning any new rows in the tables will not trigger a serialization error.
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# We then run the same purge a second time without this isolation level to
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# purge any of those rows which were added during the first.
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logger.info("[purge] Starting initial main purge of [1/2]")
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state_groups_to_delete = await self.db_pool.runInteraction(
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"purge_room",
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self._purge_room_txn,
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room_id=room_id,
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isolation_level=IsolationLevel.READ_COMMITTED,
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)
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logger.info("[purge] Starting secondary main purge of [2/2]")
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state_groups_to_delete.extend(
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await self.db_pool.runInteraction(
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"purge_room",
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self._purge_room_txn,
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room_id=room_id,
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),
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)
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logger.info("[purge] Done with main purge")
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return state_groups_to_delete
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def _purge_room_txn(self, txn: LoggingTransaction, room_id: str) -> List[int]:
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# This collides with event persistence so we cannot write new events and metadata into
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# a room while deleting it or this transaction will fail.
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if isinstance(self.database_engine, PostgresEngine):
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txn.execute(
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"SELECT room_version FROM rooms WHERE room_id = ? FOR UPDATE",
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(room_id,),
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)
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# First, fetch all the state groups that should be deleted, before
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# we delete that information.
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txn.execute(
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"""
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SELECT DISTINCT state_group FROM events
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INNER JOIN event_to_state_groups USING(event_id)
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WHERE events.room_id = ?
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""",
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(room_id,),
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)
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state_groups = [row[0] for row in txn]
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# Get all the auth chains that are referenced by events that are to be
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# deleted.
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txn.execute(
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"""
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SELECT chain_id, sequence_number FROM events
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LEFT JOIN event_auth_chains USING (event_id)
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WHERE room_id = ?
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""",
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(room_id,),
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)
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referenced_chain_id_tuples = list(txn)
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logger.info("[purge] removing from event_auth_chain_links")
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txn.executemany(
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"""
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DELETE FROM event_auth_chain_links WHERE
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origin_chain_id = ? AND origin_sequence_number = ?
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""",
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referenced_chain_id_tuples,
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)
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# Now we delete tables which lack an index on room_id but have one on event_id
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for table in (
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"event_auth",
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"event_edges",
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"event_json",
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"event_push_actions_staging",
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"event_relations",
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"event_to_state_groups",
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"event_auth_chains",
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"event_auth_chain_to_calculate",
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"redactions",
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"rejections",
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"state_events",
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):
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logger.info("[purge] removing from %s", table)
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txn.execute(
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"""
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DELETE FROM %s WHERE event_id IN (
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SELECT event_id FROM events WHERE room_id=?
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)
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"""
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% (table,),
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(room_id,),
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)
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# next, the tables with an index on room_id (or no useful index)
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for table in (
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"current_state_events",
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"destination_rooms",
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"event_backward_extremities",
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"event_forward_extremities",
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"event_push_actions",
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"event_search",
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"event_failed_pull_attempts",
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# Note: the partial state tables have foreign keys between each other, and to
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# `events` and `rooms`. We need to delete from them in the right order.
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"partial_state_events",
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"partial_state_rooms_servers",
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"partial_state_rooms",
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# Note: the _membership(s) tables have foreign keys to the `events` table
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# so must be deleted first.
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"local_current_membership",
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"room_memberships",
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"events",
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"federation_inbound_events_staging",
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"receipts_graph",
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"receipts_linearized",
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"room_aliases",
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"room_depth",
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"room_stats_state",
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"room_stats_current",
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"room_stats_earliest_token",
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"stream_ordering_to_exterm",
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"users_in_public_rooms",
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"users_who_share_private_rooms",
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# no useful index, but let's clear them anyway
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"appservice_room_list",
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"e2e_room_keys",
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"event_push_summary",
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"pusher_throttle",
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"room_account_data",
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"room_tags",
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# "rooms" happens last, to keep the foreign keys in the other tables
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# happy
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"rooms",
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):
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logger.info("[purge] removing from %s", table)
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txn.execute("DELETE FROM %s WHERE room_id=?" % (table,), (room_id,))
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# Other tables we do NOT need to clear out:
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#
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# - blocked_rooms
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# This is important, to make sure that we don't accidentally rejoin a blocked
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# room after it was purged
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#
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# - user_directory
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# This has a room_id column, but it is unused
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#
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# Other tables that we might want to consider clearing out include:
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#
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# - event_reports
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# Given that these are intended for abuse management my initial
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# inclination is to leave them in place.
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#
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# - current_state_delta_stream
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# - ex_outlier_stream
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# - room_tags_revisions
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# The problem with these is that they are largeish and there is no room_id
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# index on them. In any case we should be clearing out 'stream' tables
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# periodically anyway (https://github.com/matrix-org/synapse/issues/5888)
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self._invalidate_caches_for_room_and_stream(txn, room_id)
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return state_groups
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