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Merge pull request #7337 from matrix-org/rav/fix_update_limit_assertion

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Fix assertions being thrown by the EventsStream update function
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Richard van der Hoff 2020-04-24 14:00:29 +01:00 committed by GitHub
commit 69a1ac00b2
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5 changed files with 146 additions and 43 deletions
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1
changelog.d/7337.bugfix Normal file
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@ -0,0 +1 @@
Fix a bug where event updates might not be sent over replication to worker processes after the stream falls behind.

12
synapse/replication/http/streams.py
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@ -28,7 +28,7 @@ class ReplicationGetStreamUpdates(ReplicationEndpoint):
The API looks like:
GET /_synapse/replication/get_repl_stream_updates/events?from_token=0&to_token=10&limit=100
GET /_synapse/replication/get_repl_stream_updates/<stream name>?from_token=0&to_token=10
200 OK
@ -38,6 +38,9 @@ class ReplicationGetStreamUpdates(ReplicationEndpoint):
limited: False,
}
If there are more rows than can sensibly be returned in one lump, `limited` will be
set to true, and the caller should call again with a new `from_token`.
"""
NAME = "get_repl_stream_updates"
@ -52,8 +55,8 @@ class ReplicationGetStreamUpdates(ReplicationEndpoint):
self.streams = hs.get_replication_streamer().get_streams()
@staticmethod
def _serialize_payload(stream_name, from_token, upto_token, limit):
return {"from_token": from_token, "upto_token": upto_token, "limit": limit}
def _serialize_payload(stream_name, from_token, upto_token):
return {"from_token": from_token, "upto_token": upto_token}
async def _handle_request(self, request, stream_name):
stream = self.streams.get(stream_name)
@ -62,10 +65,9 @@ class ReplicationGetStreamUpdates(ReplicationEndpoint):
from_token = parse_integer(request, "from_token", required=True)
upto_token = parse_integer(request, "upto_token", required=True)
limit = parse_integer(request, "limit", required=True)
updates, upto_token, limited = await stream.get_updates_since(
from_token, upto_token, limit
from_token, upto_token
)
return (

19
synapse/replication/tcp/streams/_base.py
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@ -24,8 +24,8 @@ from synapse.replication.http.streams import ReplicationGetStreamUpdates
logger = logging.getLogger(__name__)
MAX_EVENTS_BEHIND = 500000
# the number of rows to request from an update_function.
_STREAM_UPDATE_TARGET_ROW_COUNT = 100
# Some type aliases to make things a bit easier.
@ -56,7 +56,11 @@ StreamUpdateResult = Tuple[List[Tuple[Token, StreamRow]], Token, bool]
# * from_token: the previous stream token: the starting point for fetching the
# updates
# * to_token: the new stream token: the point to get updates up to
# * limit: the maximum number of rows to return
# * target_row_count: a target for the number of rows to be returned.
#
# The update_function is expected to return up to _approximately_ target_row_count rows.
# If there are more updates available, it should set `limited` in the result, and
# it will be called again to get the next batch.
#
UpdateFunction = Callable[[Token, Token, int], Awaitable[StreamUpdateResult]]
@ -138,7 +142,7 @@ class Stream(object):
return updates, current_token, limited
async def get_updates_since(
self, from_token: Token, upto_token: Token, limit: int = 100
self, from_token: Token, upto_token: Token
) -> StreamUpdateResult:
"""Like get_updates except allows specifying from when we should
stream updates
@ -156,7 +160,7 @@ class Stream(object):
return [], upto_token, False
updates, upto_token, limited = await self.update_function(
from_token, upto_token, limit,
from_token, upto_token, _STREAM_UPDATE_TARGET_ROW_COUNT,
)
return updates, upto_token, limited
@ -193,10 +197,7 @@ def make_http_update_function(hs, stream_name: str) -> UpdateFunction:
from_token: int, upto_token: int, limit: int
) -> StreamUpdateResult:
result = await client(
stream_name=stream_name,
from_token=from_token,
upto_token=upto_token,
limit=limit,
stream_name=stream_name, from_token=from_token, upto_token=upto_token,
)
return result["updates"], result["upto_token"], result["limited"]

111
synapse/replication/tcp/streams/events.py
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@ -15,11 +15,12 @@
# limitations under the License.
import heapq
from typing import Iterable, Tuple, Type
from collections import Iterable
from typing import List, Tuple, Type
import attr
from ._base import Stream, Token, db_query_to_update_function
from ._base import Stream, StreamUpdateResult, Token
"""Handling of the 'events' replication stream
@ -117,30 +118,106 @@ class EventsStream(Stream):
def __init__(self, hs):
self._store = hs.get_datastore()
super().__init__(
self._store.get_current_events_token,
db_query_to_update_function(self._update_function),
self._store.get_current_events_token, self._update_function,
)
async def _update_function(
self, from_token: Token, current_token: Token, limit: int
) -> Iterable[tuple]:
self, from_token: Token, current_token: Token, target_row_count: int
) -> StreamUpdateResult:
# the events stream merges together three separate sources:
# * new events
# * current_state changes
# * events which were previously outliers, but have now been de-outliered.
#
# The merge operation is complicated by the fact that we only have a single
# "stream token" which is supposed to indicate how far we have got through
# all three streams. It's therefore no good to return rows 1-1000 from the
# "new events" table if the state_deltas are limited to rows 1-100 by the
# target_row_count.
#
# In other words: we must pick a new upper limit, and must return *all* rows
# up to that point for each of the three sources.
#
# Start by trying to split the target_row_count up. We expect to have a
# negligible number of ex-outliers, and a rough approximation based on recent
# traffic on sw1v.org shows that there are approximately the same number of
# event rows between a given pair of stream ids as there are state
# updates, so let's split our target_row_count among those two types. The target
# is only an approximation - it doesn't matter if we end up going a bit over it.
target_row_count //= 2
# now we fetch up to that many rows from the events table
event_rows = await self._store.get_all_new_forward_event_rows(
from_token, current_token, limit
)
event_updates = (
(row[0], EventsStreamEventRow.TypeId, row[1:]) for row in event_rows
)
from_token, current_token, target_row_count
) # type: List[Tuple]
# we rely on get_all_new_forward_event_rows strictly honouring the limit, so
# that we know it is safe to just take upper_limit = event_rows[-1][0].
assert (
len(event_rows) <= target_row_count
), "get_all_new_forward_event_rows did not honour row limit"
# if we hit the limit on event_updates, there's no point in going beyond the
# last stream_id in the batch for the other sources.
if len(event_rows) == target_row_count:
limited = True
upper_limit = event_rows[-1][0] # type: int
else:
limited = False
upper_limit = current_token
# next up is the state delta table
state_rows = await self._store.get_all_updated_current_state_deltas(
from_token, current_token, limit
)
from_token, upper_limit, target_row_count
) # type: List[Tuple]
# again, if we've hit the limit there, we'll need to limit the other sources
assert len(state_rows) < target_row_count
if len(state_rows) == target_row_count:
assert state_rows[-1][0] <= upper_limit
upper_limit = state_rows[-1][0]
limited = True
# FIXME: is it a given that there is only one row per stream_id in the
# state_deltas table (so that we can be sure that we have got all of the
# rows for upper_limit)?
# finally, fetch the ex-outliers rows. We assume there are few enough of these
# not to bother with the limit.
ex_outliers_rows = await self._store.get_ex_outlier_stream_rows(
from_token, upper_limit
) # type: List[Tuple]
# we now need to turn the raw database rows returned into tuples suitable
# for the replication protocol (basically, we add an identifier to
# distinguish the row type). At the same time, we can limit the event_rows
# to the max stream_id from state_rows.
event_updates = (
(stream_id, (EventsStreamEventRow.TypeId, rest))
for (stream_id, *rest) in event_rows
if stream_id <= upper_limit
) # type: Iterable[Tuple[int, Tuple]]
state_updates = (
(row[0], EventsStreamCurrentStateRow.TypeId, row[1:]) for row in state_rows
)
(stream_id, (EventsStreamCurrentStateRow.TypeId, rest))
for (stream_id, *rest) in state_rows
) # type: Iterable[Tuple[int, Tuple]]
all_updates = heapq.merge(event_updates, state_updates)
ex_outliers_updates = (
(stream_id, (EventsStreamEventRow.TypeId, rest))
for (stream_id, *rest) in ex_outliers_rows
) # type: Iterable[Tuple[int, Tuple]]
return all_updates
# we need to return a sorted list, so merge them together.
updates = list(heapq.merge(event_updates, state_updates, ex_outliers_updates))
return updates, upper_limit, limited
@classmethod
def parse_row(cls, row):

46
synapse/storage/data_stores/main/events_worker.py
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@ -973,8 +973,18 @@ class EventsWorkerStore(SQLBaseStore):
return self._stream_id_gen.get_current_token()
def get_all_new_forward_event_rows(self, last_id, current_id, limit):
if last_id == current_id:
return defer.succeed([])
"""Returns new events, for the Events replication stream
Args:
last_id: the last stream_id from the previous batch.
current_id: the maximum stream_id to return up to
limit: the maximum number of rows to return
Returns: Deferred[List[Tuple]]
a list of events stream rows. Each tuple consists of a stream id as
the first element, followed by fields suitable for casting into an
EventsStreamRow.
"""
def get_all_new_forward_event_rows(txn):
sql = (
@ -989,13 +999,26 @@ class EventsWorkerStore(SQLBaseStore):
" LIMIT ?"
)
txn.execute(sql, (last_id, current_id, limit))
new_event_updates = txn.fetchall()
return txn.fetchall()
if len(new_event_updates) == limit:
upper_bound = new_event_updates[-1][0]
else:
upper_bound = current_id
return self.db.runInteraction(
"get_all_new_forward_event_rows", get_all_new_forward_event_rows
)
def get_ex_outlier_stream_rows(self, last_id, current_id):
"""Returns de-outliered events, for the Events replication stream
Args:
last_id: the last stream_id from the previous batch.
current_id: the maximum stream_id to return up to
Returns: Deferred[List[Tuple]]
a list of events stream rows. Each tuple consists of a stream id as
the first element, followed by fields suitable for casting into an
EventsStreamRow.
"""
def get_ex_outlier_stream_rows_txn(txn):
sql = (
"SELECT event_stream_ordering, e.event_id, e.room_id, e.type,"
" state_key, redacts, relates_to_id"
@ -1006,15 +1029,14 @@ class EventsWorkerStore(SQLBaseStore):
" LEFT JOIN event_relations USING (event_id)"
" WHERE ? < event_stream_ordering"
" AND event_stream_ordering <= ?"
" ORDER BY event_stream_ordering DESC"
" ORDER BY event_stream_ordering ASC"
)
txn.execute(sql, (last_id, upper_bound))
new_event_updates.extend(txn)
return new_event_updates
txn.execute(sql, (last_id, current_id))
return txn.fetchall()
return self.db.runInteraction(
"get_all_new_forward_event_rows", get_all_new_forward_event_rows
"get_ex_outlier_stream_rows", get_ex_outlier_stream_rows_txn
)
def get_all_new_backfill_event_rows(self, last_id, current_id, limit):