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Merge pull request #4006 from matrix-org/erikj/purge_state_groups 

Delete unreferenced state groups during purge
This commit is contained in:
Erik Johnston 2018-10-30 16:58:22 +00:00 committed by GitHub
parent 0dce9e1379 ad88460e0d
commit 0794504bce
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5 changed files with 136 additions and 46 deletions
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1
changelog.d/4006.misc Normal file
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@ -0,0 +1 @@
Delete unreferenced state groups during history purge

151
synapse/storage/events.py
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@ -38,6 +38,7 @@ from synapse.state import StateResolutionStore
from synapse.storage.background_updates import BackgroundUpdateStore
from synapse.storage.event_federation import EventFederationStore
from synapse.storage.events_worker import EventsWorkerStore
from synapse.storage.state import StateGroupWorkerStore
from synapse.types import RoomStreamToken, get_domain_from_id
from synapse.util import batch_iter
from synapse.util.async_helpers import ObservableDeferred
@ -205,7 +206,8 @@ def _retry_on_integrity_error(func):
# inherits from EventFederationStore so that we can call _update_backward_extremities
# and _handle_mult_prev_events (though arguably those could both be moved in here)
class EventsStore(EventFederationStore, EventsWorkerStore, BackgroundUpdateStore):
class EventsStore(StateGroupWorkerStore, EventFederationStore, EventsWorkerStore,
BackgroundUpdateStore):
EVENT_ORIGIN_SERVER_TS_NAME = "event_origin_server_ts"
EVENT_FIELDS_SENDER_URL_UPDATE_NAME = "event_fields_sender_url"
@ -2034,54 +2036,36 @@ class EventsStore(EventFederationStore, EventsWorkerStore, BackgroundUpdateStore
logger.info("[purge] finding redundant state groups")
# Get all state groups that are only referenced by events that are
# to be deleted.
# This works by first getting state groups that we may want to delete,
# joining against event_to_state_groups to get events that use that
# state group, then left joining against events_to_purge again. Any
# state group where the left join produce *no nulls* are referenced
# only by events that are going to be purged.
# Get all state groups that are referenced by events that are to be
# deleted. We then go and check if they are referenced by other events
# or state groups, and if not we delete them.
txn.execute("""
SELECT state_group FROM
(
SELECT DISTINCT state_group FROM events_to_purge
INNER JOIN event_to_state_groups USING (event_id)
) AS sp
INNER JOIN event_to_state_groups USING (state_group)
LEFT JOIN events_to_purge AS ep USING (event_id)
GROUP BY state_group
HAVING SUM(CASE WHEN ep.event_id IS NULL THEN 1 ELSE 0 END) = 0
""")
state_rows = txn.fetchall()
logger.info("[purge] found %i redundant state groups", len(state_rows))
# make a set of the redundant state groups, so that we can look them up
# efficiently
state_groups_to_delete = set([sg for sg, in state_rows])
# Now we get all the state groups that rely on these state groups
logger.info("[purge] finding state groups which depend on redundant"
" state groups")
remaining_state_groups = []
for i in range(0, len(state_rows), 100):
chunk = [sg for sg, in state_rows[i:i + 100]]
# look for state groups whose prev_state_group is one we are about
# to delete
rows = self._simple_select_many_txn(
txn,
table="state_group_edges",
column="prev_state_group",
iterable=chunk,
retcols=["state_group"],
keyvalues={},
referenced_state_groups = set(sg for sg, in txn)
logger.info(
"[purge] found %i referenced state groups",
len(referenced_state_groups),
)
remaining_state_groups.extend(
row["state_group"] for row in rows
# exclude state groups we are about to delete: no point in
# updating them
if row["state_group"] not in state_groups_to_delete
logger.info("[purge] finding state groups that can be deleted")
state_groups_to_delete, remaining_state_groups = (
self._find_unreferenced_groups_during_purge(
txn, referenced_state_groups,
)
)
logger.info(
"[purge] found %i state groups to delete",
len(state_groups_to_delete),
)
logger.info(
"[purge] de-delta-ing %i remaining state groups",
len(remaining_state_groups),
)
# Now we turn the state groups that reference to-be-deleted state
@ -2127,11 +2111,11 @@ class EventsStore(EventFederationStore, EventsWorkerStore, BackgroundUpdateStore
logger.info("[purge] removing redundant state groups")
txn.executemany(
"DELETE FROM state_groups_state WHERE state_group = ?",
state_rows
((sg,) for sg in state_groups_to_delete),
)
txn.executemany(
"DELETE FROM state_groups WHERE id = ?",
state_rows
((sg,) for sg in state_groups_to_delete),
)
logger.info("[purge] removing events from event_to_state_groups")
@ -2227,6 +2211,85 @@ class EventsStore(EventFederationStore, EventsWorkerStore, BackgroundUpdateStore
logger.info("[purge] done")
def _find_unreferenced_groups_during_purge(self, txn, state_groups):
"""Used when purging history to figure out which state groups can be
deleted and which need to be de-delta'ed (due to one of its prev groups
being scheduled for deletion).
Args:
txn
state_groups (set[int]): Set of state groups referenced by events
that are going to be deleted.
Returns:
tuple[set[int], set[int]]: The set of state groups that can be
deleted and the set of state groups that need to be de-delta'ed
"""
# Graph of state group -> previous group
graph = {}
# 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
# Check if state groups are referenced
sql = """
SELECT DISTINCT state_group FROM event_to_state_groups
LEFT JOIN events_to_purge AS ep USING (event_id)
WHERE state_group IN (%s) AND ep.event_id IS NULL
""" % (",".join("?" for _ in current_search),)
txn.execute(sql, list(current_search))
referenced = set(sg for sg, in txn)
referenced_groups |= referenced
# We don't continue iterating up the state group graphs for state
# groups that are referenced.
current_search -= referenced
rows = self._simple_select_many_txn(
txn,
table="state_group_edges",
column="prev_state_group",
iterable=current_search,
keyvalues={},
retcols=("prev_state_group", "state_group",),
)
prevs = set(row["state_group"] for row in rows)
# We don't bother re-handling groups we've already seen
prevs -= state_groups_seen
next_to_search |= prevs
state_groups_seen |= prevs
for row in rows:
# Note: Each state group can have at most one prev group
graph[row["state_group"]] = row["prev_state_group"]
to_delete = state_groups_seen - referenced_groups
to_dedelta = set()
for sg in referenced_groups:
prev_sg = graph.get(sg)
if prev_sg and prev_sg in to_delete:
to_dedelta.add(sg)
return to_delete, to_dedelta
@defer.inlineCallbacks
def is_event_after(self, event_id1, event_id2):
"""Returns True if event_id1 is after event_id2 in the stream

2
synapse/storage/prepare_database.py
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@ -25,7 +25,7 @@ logger = logging.getLogger(__name__)
# Remember to update this number every time a change is made to database
# schema files, so the users will be informed on server restarts.
SCHEMA_VERSION = 51
SCHEMA_VERSION = 52
dir_path = os.path.abspath(os.path.dirname(__file__))

19
synapse/storage/schema/delta/52/add_event_to_state_group_index.sql Normal file
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@ -0,0 +1,19 @@
/* Copyright 2018 New Vector Ltd
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
-- This is needed to efficiently check for unreferenced state groups during
-- purge. Added events_to_state_group(state_group) index
INSERT into background_updates (update_name, progress_json)
VALUES ('event_to_state_groups_sg_index', '{}');

7
synapse/storage/state.py
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@ -1257,6 +1257,7 @@ class StateStore(StateGroupWorkerStore, BackgroundUpdateStore):
STATE_GROUP_DEDUPLICATION_UPDATE_NAME = "state_group_state_deduplication"
STATE_GROUP_INDEX_UPDATE_NAME = "state_group_state_type_index"
CURRENT_STATE_INDEX_UPDATE_NAME = "current_state_members_idx"
EVENT_STATE_GROUP_INDEX_UPDATE_NAME = "event_to_state_groups_sg_index"
def __init__(self, db_conn, hs):
super(StateStore, self).__init__(db_conn, hs)
@ -1275,6 +1276,12 @@ class StateStore(StateGroupWorkerStore, BackgroundUpdateStore):
columns=["state_key"],
where_clause="type='m.room.member'",
)
self.register_background_index_update(
self.EVENT_STATE_GROUP_INDEX_UPDATE_NAME,
index_name="event_to_state_groups_sg_index",
table="event_to_state_groups",
columns=["state_group"],
)
def _store_event_state_mappings_txn(self, txn, events_and_contexts):
state_groups = {}