Batch process handling state groups

This commit is contained in:
Erik Johnston 2018-10-12 20:43:18 +01:00
parent 67a1e315cc
commit 47a9da28ca
2 changed files with 86 additions and 95 deletions

View File

@ -37,6 +37,7 @@ from synapse.metrics.background_process_metrics import run_as_background_process
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.async_helpers import ObservableDeferred
from synapse.util.caches.descriptors import cached, cachedInlineCallbacks
@ -203,7 +204,8 @@ 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"
@ -1995,70 +1997,29 @@ 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 = []
unreferenced_state_groups = 0
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),
)
for row in rows:
sg = row["state_group"]
logger.info("[purge] finding state groups that can be deleted")
if sg in state_groups_to_delete:
# exclude state groups we are about to delete: no point in
# updating them
continue
if not self._is_state_group_referenced(txn, sg):
# Let's also delete unreferenced state groups while we're
# here, since otherwise we'd need to de-delta them
state_groups_to_delete.add(sg)
unreferenced_state_groups += 1
continue
remaining_state_groups.append(sg)
state_groups_to_delete, remaining_state_groups = self._find_unreferenced_groups(
txn, referenced_state_groups,
)
logger.info(
"[purge] found %i extra unreferenced state groups to delete",
unreferenced_state_groups,
"[purge] found %i state groups to delete",
len(state_groups_to_delete),
)
logger.info(
@ -2109,11 +2070,11 @@ 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")

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@ -1041,55 +1041,85 @@ class StateGroupWorkerStore(EventsWorkerStore, SQLBaseStore):
return count
def _is_state_group_referenced(self, txn, state_group):
"""Checks if a given state group is referenced, or is safe to delete.
def _find_unreferenced_groups(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).
A state group is referenced if it or any of its descendants are
pointed at by an event. (A descendant is a state_group whose chain of
prev_groups includes the given state_group.)
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 = {}
# We check this by doing a depth first search to look for any
# descendant referenced by `event_to_state_groups`.
# Set of events that we have found to be referenced by events
referenced_groups = set()
# State groups we need to check, contains state groups that are
# descendants of `state_group`
state_groups_to_search = [state_group]
# Set of state groups we've already seen
state_groups_seen = set(state_groups)
# Set of state groups we've already checked
state_groups_searched = set()
# 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:
lst = list(next_to_search)
current_search = set(lst[:100])
next_to_search = set(lst[100:])
while state_groups_to_search:
state_group = state_groups_to_search.pop() # Next state group to check
# Check if state groups are referenced
sql = """
SELECT state_group, count(*) 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
GROUP BY state_group
""" % (",".join("?" for _ in current_search),)
txn.execute(sql, list(current_search))
is_referenced = self._simple_select_one_onecol_txn(
txn,
table="event_to_state_groups",
keyvalues={"state_group": state_group},
retcol="event_id",
allow_none=True,
)
if is_referenced:
# A descendant is referenced by event_to_state_groups, so
# original state group is referenced.
return True
referenced = set(sg for sg, cnt in txn if cnt > 0)
referenced_groups |= referenced
state_groups_searched.add(state_group)
# We don't continue iterating up the state group graphs for state
# groups that are referenced.
current_search -= referenced
# Find all children of current state group and add to search
references = self._simple_select_onecol_txn(
rows = self._simple_select_many_txn(
txn,
table="state_group_edges",
keyvalues={"prev_state_group": state_group},
retcol="state_group",
column="prev_state_group",
iterable=current_search,
keyvalues={},
retcols=("prev_state_group", "state_group",),
)
state_groups_to_search.extend(references)
# Lets be paranoid and check for cycles
if state_groups_searched.intersection(references):
raise Exception("State group %s has cyclic dependency", state_group)
next_to_search.update(row["state_group"] for row in rows)
# We don't bother re-handling groups we've already seen
next_to_search -= state_groups_seen
state_groups_seen |= next_to_search
return False
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
class StateStore(StateGroupWorkerStore, BackgroundUpdateStore):