diff --git a/changelog.d/7337.bugfix b/changelog.d/7337.bugfix
new file mode 100644
index 0000000000..f49c600173
--- /dev/null
+++ b/changelog.d/7337.bugfix
@@ -0,0 +1 @@
+Fix a bug where event updates might not be sent over replication to worker processes after the stream falls behind.
diff --git a/synapse/replication/http/streams.py b/synapse/replication/http/streams.py
index ffd4c61993..f35cebc710 100644
--- a/synapse/replication/http/streams.py
+++ b/synapse/replication/http/streams.py
@@ -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 (
diff --git a/synapse/replication/tcp/streams/_base.py b/synapse/replication/tcp/streams/_base.py
index a860072ccf..4ae3cffb1e 100644
--- a/synapse/replication/tcp/streams/_base.py
+++ b/synapse/replication/tcp/streams/_base.py
@@ -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"]
diff --git a/synapse/replication/tcp/streams/events.py b/synapse/replication/tcp/streams/events.py
index 051114596b..aa50492569 100644
--- a/synapse/replication/tcp/streams/events.py
+++ b/synapse/replication/tcp/streams/events.py
@@ -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
- )
- state_updates = (
- (row[0], EventsStreamCurrentStateRow.TypeId, row[1:]) for row in state_rows
- )
+ 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.
- all_updates = heapq.merge(event_updates, state_updates)
+ ex_outliers_rows = await self._store.get_ex_outlier_stream_rows(
+ from_token, upper_limit
+ ) # type: List[Tuple]
- return all_updates
+ # 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 = (
+ (stream_id, (EventsStreamCurrentStateRow.TypeId, rest))
+ for (stream_id, *rest) in state_rows
+ ) # type: Iterable[Tuple[int, Tuple]]
+
+ ex_outliers_updates = (
+ (stream_id, (EventsStreamEventRow.TypeId, rest))
+ for (stream_id, *rest) in ex_outliers_rows
+ ) # type: Iterable[Tuple[int, Tuple]]
+
+ # 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):
diff --git a/synapse/storage/data_stores/main/events_worker.py b/synapse/storage/data_stores/main/events_worker.py
index accde349a7..ce8be72bfe 100644
--- a/synapse/storage/data_stores/main/events_worker.py
+++ b/synapse/storage/data_stores/main/events_worker.py
@@ -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):
|
