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Add experimental support for sharding event persister. (#8170) 

This is *not* ready for production yet. Caveats:

1. We should write some tests...
2. The stream token that we use for events can get stalled at the minimum position of all writers. This means that new events may not be processed and e.g. sent down sync streams if a writer isn't writing or is slow.
This commit is contained in:
Erik Johnston 2020-09-02 15:48:37 +01:00 committed by GitHub
parent b257c788c0
commit 82c1ee1c22
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
18 changed files with 206 additions and 77 deletions
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1
changelog.d/8170.feature Normal file
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@ -0,0 +1 @@
Add experimental support for sharding event persister.

21
synapse/config/_base.py
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@ -832,11 +832,26 @@ class ShardedWorkerHandlingConfig:
def should_handle(self, instance_name: str, key: str) -> bool:
"""Whether this instance is responsible for handling the given key.
"""
# If multiple instances are not defined we always return true.
# If multiple instances are not defined we always return true
if not self.instances or len(self.instances) == 1:
return True
return self.get_instance(key) == instance_name
def get_instance(self, key: str) -> str:
"""Get the instance responsible for handling the given key.
Note: For things like federation sending the config for which instance
is sending is known only to the sender instance if there is only one.
Therefore `should_handle` should be used where possible.
"""
if not self.instances:
return "master"
if len(self.instances) == 1:
return self.instances[0]
# We shard by taking the hash, modulo it by the number of instances and
# then checking whether this instance matches the instance at that
# index.
@ -846,7 +861,7 @@ class ShardedWorkerHandlingConfig:
dest_hash = sha256(key.encode("utf8")).digest()
dest_int = int.from_bytes(dest_hash, byteorder="little")
remainder = dest_int % (len(self.instances))
return self.instances[remainder] == instance_name
return self.instances[remainder]
__all__ = ["Config", "RootConfig", "ShardedWorkerHandlingConfig"]

1
synapse/config/_base.pyi
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@ -142,3 +142,4 @@ class ShardedWorkerHandlingConfig:
instances: List[str]
def __init__(self, instances: List[str]) -> None: ...
def should_handle(self, instance_name: str, key: str) -> bool: ...
def get_instance(self, key: str) -> str: ...

37
synapse/config/workers.py
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@ -13,12 +13,24 @@
# See the License for the specific language governing permissions and
# limitations under the License.
from typing import List, Union
import attr
from ._base import Config, ConfigError, ShardedWorkerHandlingConfig
from .server import ListenerConfig, parse_listener_def
def _instance_to_list_converter(obj: Union[str, List[str]]) -> List[str]:
"""Helper for allowing parsing a string or list of strings to a config
option expecting a list of strings.
"""
if isinstance(obj, str):
return [obj]
return obj
@attr.s
class InstanceLocationConfig:
"""The host and port to talk to an instance via HTTP replication.
@ -33,11 +45,13 @@ class WriterLocations:
"""Specifies the instances that write various streams.
Attributes:
events: The instance that writes to the event and backfill streams.
events: The instance that writes to the typing stream.
events: The instances that write to the event and backfill streams.
typing: The instance that writes to the typing stream.
"""
events = attr.ib(default="master", type=str)
events = attr.ib(
default=["master"], type=List[str], converter=_instance_to_list_converter
)
typing = attr.ib(default="master", type=str)
@ -105,15 +119,18 @@ class WorkerConfig(Config):
writers = config.get("stream_writers") or {}
self.writers = WriterLocations(**writers)
# Check that the configured writer for events and typing also appears in
# Check that the configured writers for events and typing also appears in
# `instance_map`.
for stream in ("events", "typing"):
instance = getattr(self.writers, stream)
if instance != "master" and instance not in self.instance_map:
raise ConfigError(
"Instance %r is configured to write %s but does not appear in `instance_map` config."
% (instance, stream)
)
instances = _instance_to_list_converter(getattr(self.writers, stream))
for instance in instances:
if instance != "master" and instance not in self.instance_map:
raise ConfigError(
"Instance %r is configured to write %s but does not appear in `instance_map` config."
% (instance, stream)
)
self.events_shard_config = ShardedWorkerHandlingConfig(self.writers.events)
def generate_config_section(self, config_dir_path, server_name, **kwargs):
return """\

44
synapse/handlers/federation.py
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@ -923,7 +923,8 @@ class FederationHandler(BaseHandler):
)
)
await self._handle_new_events(dest, ev_infos, backfilled=True)
if ev_infos:
await self._handle_new_events(dest, room_id, ev_infos, backfilled=True)
# Step 2: Persist the rest of the events in the chunk one by one
events.sort(key=lambda e: e.depth)
@ -1216,7 +1217,7 @@ class FederationHandler(BaseHandler):
event_infos.append(_NewEventInfo(event, None, auth))
await self._handle_new_events(
destination, event_infos,
destination, room_id, event_infos,
)
def _sanity_check_event(self, ev):
@ -1363,15 +1364,15 @@ class FederationHandler(BaseHandler):
)
max_stream_id = await self._persist_auth_tree(
origin, auth_chain, state, event, room_version_obj
origin, room_id, auth_chain, state, event, room_version_obj
)
# We wait here until this instance has seen the events come down
# replication (if we're using replication) as the below uses caches.
#
# TODO: Currently the events stream is written to from master
await self._replication.wait_for_stream_position(
self.config.worker.writers.events, "events", max_stream_id
self.config.worker.events_shard_config.get_instance(room_id),
"events",
max_stream_id,
)
# Check whether this room is the result of an upgrade of a room we already know
@ -1625,7 +1626,7 @@ class FederationHandler(BaseHandler):
)
context = await self.state_handler.compute_event_context(event)
await self.persist_events_and_notify([(event, context)])
await self.persist_events_and_notify(event.room_id, [(event, context)])
return event
@ -1652,7 +1653,9 @@ class FederationHandler(BaseHandler):
await self.federation_client.send_leave(host_list, event)
context = await self.state_handler.compute_event_context(event)
stream_id = await self.persist_events_and_notify([(event, context)])
stream_id = await self.persist_events_and_notify(
event.room_id, [(event, context)]
)
return event, stream_id
@ -1900,7 +1903,7 @@ class FederationHandler(BaseHandler):
)
await self.persist_events_and_notify(
[(event, context)], backfilled=backfilled
event.room_id, [(event, context)], backfilled=backfilled
)
except Exception:
run_in_background(
@ -1913,6 +1916,7 @@ class FederationHandler(BaseHandler):
async def _handle_new_events(
self,
origin: str,
room_id: str,
event_infos: Iterable[_NewEventInfo],
backfilled: bool = False,
) -> None:
@ -1944,6 +1948,7 @@ class FederationHandler(BaseHandler):
)
await self.persist_events_and_notify(
room_id,
[
(ev_info.event, context)
for ev_info, context in zip(event_infos, contexts)
@ -1954,6 +1959,7 @@ class FederationHandler(BaseHandler):
async def _persist_auth_tree(
self,
origin: str,
room_id: str,
auth_events: List[EventBase],
state: List[EventBase],
event: EventBase,
@ -1968,6 +1974,7 @@ class FederationHandler(BaseHandler):
Args:
origin: Where the events came from
room_id,
auth_events
state
event
@ -2042,17 +2049,20 @@ class FederationHandler(BaseHandler):
events_to_context[e.event_id].rejected = RejectedReason.AUTH_ERROR
await self.persist_events_and_notify(
room_id,
[
(e, events_to_context[e.event_id])
for e in itertools.chain(auth_events, state)
]
],
)
new_event_context = await self.state_handler.compute_event_context(
event, old_state=state
)
return await self.persist_events_and_notify([(event, new_event_context)])
return await self.persist_events_and_notify(
room_id, [(event, new_event_context)]
)
async def _prep_event(
self,
@ -2903,6 +2913,7 @@ class FederationHandler(BaseHandler):
async def persist_events_and_notify(
self,
room_id: str,
event_and_contexts: Sequence[Tuple[EventBase, EventContext]],
backfilled: bool = False,
) -> int:
@ -2910,14 +2921,19 @@ class FederationHandler(BaseHandler):
necessary.
Args:
event_and_contexts:
room_id: The room ID of events being persisted.
event_and_contexts: Sequence of events with their associated
context that should be persisted. All events must belong to
the same room.
backfilled: Whether these events are a result of
backfilling or not
"""
if self.config.worker.writers.events != self._instance_name:
instance = self.config.worker.events_shard_config.get_instance(room_id)
if instance != self._instance_name:
result = await self._send_events(
instance_name=self.config.worker.writers.events,
instance_name=instance,
store=self.store,
room_id=room_id,
event_and_contexts=event_and_contexts,
backfilled=backfilled,
)

14
synapse/handlers/message.py
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@ -376,9 +376,8 @@ class EventCreationHandler(object):
self.notifier = hs.get_notifier()
self.config = hs.config
self.require_membership_for_aliases = hs.config.require_membership_for_aliases
self._is_event_writer = (
self.config.worker.writers.events == hs.get_instance_name()
)
self._events_shard_config = self.config.worker.events_shard_config
self._instance_name = hs.get_instance_name()
self.room_invite_state_types = self.hs.config.room_invite_state_types
@ -904,9 +903,10 @@ class EventCreationHandler(object):
try:
# If we're a worker we need to hit out to the master.
if not self._is_event_writer:
writer_instance = self._events_shard_config.get_instance(event.room_id)
if writer_instance != self._instance_name:
result = await self.send_event(
instance_name=self.config.worker.writers.events,
instance_name=writer_instance,
event_id=event.event_id,
store=self.store,
requester=requester,
@ -974,7 +974,9 @@ class EventCreationHandler(object):
This should only be run on the instance in charge of persisting events.
"""
assert self._is_event_writer
assert self._events_shard_config.should_handle(
self._instance_name, event.room_id
)
if ratelimit:
# We check if this is a room admin redacting an event so that we

14
synapse/handlers/room.py
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@ -804,7 +804,9 @@ class RoomCreationHandler(BaseHandler):
# Always wait for room creation to progate before returning
await self._replication.wait_for_stream_position(
self.hs.config.worker.writers.events, "events", last_stream_id
self.hs.config.worker.events_shard_config.get_instance(room_id),
"events",
last_stream_id,
)
return result, last_stream_id
@ -1260,10 +1262,10 @@ class RoomShutdownHandler(object):
# We now wait for the create room to come back in via replication so
# that we can assume that all the joins/invites have propogated before
# we try and auto join below.
#
# TODO: Currently the events stream is written to from master
await self._replication.wait_for_stream_position(
self.hs.config.worker.writers.events, "events", stream_id
self.hs.config.worker.events_shard_config.get_instance(new_room_id),
"events",
stream_id,
)
else:
new_room_id = None
@ -1293,7 +1295,9 @@ class RoomShutdownHandler(object):
# Wait for leave to come in over replication before trying to forget.
await self._replication.wait_for_stream_position(
self.hs.config.worker.writers.events, "events", stream_id
self.hs.config.worker.events_shard_config.get_instance(room_id),
"events",
stream_id,
)
await self.room_member_handler.forget(target_requester.user, room_id)

7
synapse/handlers/room_member.py
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@ -82,13 +82,6 @@ class RoomMemberHandler(object):
self._enable_lookup = hs.config.enable_3pid_lookup
self.allow_per_room_profiles = self.config.allow_per_room_profiles
self._event_stream_writer_instance = hs.config.worker.writers.events
self._is_on_event_persistence_instance = (
self._event_stream_writer_instance == hs.get_instance_name()
)
if self._is_on_event_persistence_instance:
self.persist_event_storage = hs.get_storage().persistence
self._join_rate_limiter_local = Ratelimiter(
clock=self.clock,
rate_hz=hs.config.ratelimiting.rc_joins_local.per_second,

12
synapse/replication/http/federation.py
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@ -65,10 +65,11 @@ class ReplicationFederationSendEventsRestServlet(ReplicationEndpoint):
self.federation_handler = hs.get_handlers().federation_handler
@staticmethod
async def _serialize_payload(store, event_and_contexts, backfilled):
async def _serialize_payload(store, room_id, event_and_contexts, backfilled):
"""
Args:
store
room_id (str)
event_and_contexts (list[tuple[FrozenEvent, EventContext]])
backfilled (bool): Whether or not the events are the result of
backfilling
@ -88,7 +89,11 @@ class ReplicationFederationSendEventsRestServlet(ReplicationEndpoint):
}
)
payload = {"events": event_payloads, "backfilled": backfilled}
payload = {
"events": event_payloads,
"backfilled": backfilled,
"room_id": room_id,
}
return payload
@ -96,6 +101,7 @@ class ReplicationFederationSendEventsRestServlet(ReplicationEndpoint):
with Measure(self.clock, "repl_fed_send_events_parse"):
content = parse_json_object_from_request(request)
room_id = content["room_id"]
backfilled = content["backfilled"]
event_payloads = content["events"]
@ -120,7 +126,7 @@ class ReplicationFederationSendEventsRestServlet(ReplicationEndpoint):
logger.info("Got %d events from federation", len(event_and_contexts))
max_stream_id = await self.federation_handler.persist_events_and_notify(
event_and_contexts, backfilled
room_id, event_and_contexts, backfilled
)
return 200, {"max_stream_id": max_stream_id}

2
synapse/replication/tcp/handler.py
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@ -109,7 +109,7 @@ class ReplicationCommandHandler:
if isinstance(stream, (EventsStream, BackfillStream)):
# Only add EventStream and BackfillStream as a source on the
# instance in charge of event persistence.
if hs.config.worker.writers.events == hs.get_instance_name():
if hs.get_instance_name() in hs.config.worker.writers.events:
self._streams_to_replicate.append(stream)
continue

4
synapse/replication/tcp/streams/events.py
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@ -19,7 +19,7 @@ from typing import List, Tuple, Type
import attr
from ._base import Stream, StreamUpdateResult, Token, current_token_without_instance
from ._base import Stream, StreamUpdateResult, Token
"""Handling of the 'events' replication stream
@ -117,7 +117,7 @@ class EventsStream(Stream):
self._store = hs.get_datastore()
super().__init__(
hs.get_instance_name(),
current_token_without_instance(self._store.get_current_events_token),
self._store._stream_id_gen.get_current_token_for_writer,
self._update_function,
)

2
synapse/storage/databases/__init__.py
View File

@ -68,7 +68,7 @@ class Databases(object):
# If we're on a process that can persist events also
# instantiate a `PersistEventsStore`
if hs.config.worker.writers.events == hs.get_instance_name():
if hs.get_instance_name() in hs.config.worker.writers.events:
persist_events = PersistEventsStore(hs, database, main)
if "state" in database_config.databases:

2
synapse/storage/databases/main/event_federation.py
View File

@ -438,7 +438,7 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, SQLBas
"""
if stream_ordering <= self.stream_ordering_month_ago:
raise StoreError(400, "stream_ordering too old")
raise StoreError(400, "stream_ordering too old %s" % (stream_ordering,))
sql = """
SELECT event_id FROM stream_ordering_to_exterm

4
synapse/storage/databases/main/events.py
View File

@ -97,6 +97,7 @@ class PersistEventsStore:
self.store = main_data_store
self.database_engine = db.engine
self._clock = hs.get_clock()
self._instance_name = hs.get_instance_name()
self._ephemeral_messages_enabled = hs.config.enable_ephemeral_messages
self.is_mine_id = hs.is_mine_id
@ -108,7 +109,7 @@ class PersistEventsStore:
# This should only exist on instances that are configured to write
assert (
hs.config.worker.writers.events == hs.get_instance_name()
hs.get_instance_name() in hs.config.worker.writers.events
), "Can only instantiate EventsStore on master"
async def _persist_events_and_state_updates(
@ -800,6 +801,7 @@ class PersistEventsStore:
table="events",
values=[
{
"instance_name": self._instance_name,
"stream_ordering": event.internal_metadata.stream_ordering,
"topological_ordering": event.depth,
"depth": event.depth,

66
synapse/storage/databases/main/events_worker.py
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@ -42,7 +42,8 @@ from synapse.replication.tcp.streams import BackfillStream
from synapse.replication.tcp.streams.events import EventsStream
from synapse.storage._base import SQLBaseStore, db_to_json, make_in_list_sql_clause
from synapse.storage.database import DatabasePool
from synapse.storage.util.id_generators import StreamIdGenerator
from synapse.storage.engines import PostgresEngine
from synapse.storage.util.id_generators import MultiWriterIdGenerator, StreamIdGenerator
from synapse.types import Collection, get_domain_from_id
from synapse.util.caches.descriptors import Cache, cached
from synapse.util.iterutils import batch_iter
@ -78,27 +79,54 @@ class EventsWorkerStore(SQLBaseStore):
def __init__(self, database: DatabasePool, db_conn, hs):
super(EventsWorkerStore, self).__init__(database, db_conn, hs)
if hs.config.worker.writers.events == hs.get_instance_name():
# We are the process in charge of generating stream ids for events,
# so instantiate ID generators based on the database
self._stream_id_gen = StreamIdGenerator(
db_conn, "events", "stream_ordering",
if isinstance(database.engine, PostgresEngine):
# If we're using Postgres than we can use `MultiWriterIdGenerator`
# regardless of whether this process writes to the streams or not.
self._stream_id_gen = MultiWriterIdGenerator(
db_conn=db_conn,
db=database,
instance_name=hs.get_instance_name(),
table="events",
instance_column="instance_name",
id_column="stream_ordering",
sequence_name="events_stream_seq",
)
self._backfill_id_gen = StreamIdGenerator(
db_conn,
"events",
"stream_ordering",
step=-1,
extra_tables=[("ex_outlier_stream", "event_stream_ordering")],
self._backfill_id_gen = MultiWriterIdGenerator(
db_conn=db_conn,
db=database,
instance_name=hs.get_instance_name(),
table="events",
instance_column="instance_name",
id_column="stream_ordering",
sequence_name="events_backfill_stream_seq",
positive=False,
)
else:
# Another process is in charge of persisting events and generating
# stream IDs: rely on the replication streams to let us know which
# IDs we can process.
self._stream_id_gen = SlavedIdTracker(db_conn, "events", "stream_ordering")
self._backfill_id_gen = SlavedIdTracker(
db_conn, "events", "stream_ordering", step=-1
)
# We shouldn't be running in worker mode with SQLite, but its useful
# to support it for unit tests.
#
# If this process is the writer than we need to use
# `StreamIdGenerator`, otherwise we use `SlavedIdTracker` which gets
# updated over replication. (Multiple writers are not supported for
# SQLite).
if hs.get_instance_name() in hs.config.worker.writers.events:
self._stream_id_gen = StreamIdGenerator(
db_conn, "events", "stream_ordering",
)
self._backfill_id_gen = StreamIdGenerator(
db_conn,
"events",
"stream_ordering",
step=-1,
extra_tables=[("ex_outlier_stream", "event_stream_ordering")],
)
else:
self._stream_id_gen = SlavedIdTracker(
db_conn, "events", "stream_ordering"
)
self._backfill_id_gen = SlavedIdTracker(
db_conn, "events", "stream_ordering", step=-1
)
self._get_event_cache = Cache(
"*getEvent*",

16
synapse/storage/databases/main/schema/delta/58/14events_instance_name.sql Normal file
View File

@ -0,0 +1,16 @@
/* Copyright 2020 The Matrix.org Foundation C.I.C.
*
* 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.
*/
ALTER TABLE events ADD COLUMN instance_name TEXT;

26
synapse/storage/databases/main/schema/delta/58/14events_instance_name.sql.postgres Normal file
View File

@ -0,0 +1,26 @@
/* Copyright 2020 The Matrix.org Foundation C.I.C.
*
* 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.
*/
CREATE SEQUENCE IF NOT EXISTS events_stream_seq;
SELECT setval('events_stream_seq', (
SELECT COALESCE(MAX(stream_ordering), 1) FROM events
));
CREATE SEQUENCE IF NOT EXISTS events_backfill_stream_seq;
SELECT setval('events_backfill_stream_seq', (
SELECT COALESCE(-MIN(stream_ordering), 1) FROM events
));

10
synapse/storage/util/id_generators.py
View File

@ -231,8 +231,12 @@ class MultiWriterIdGenerator:
# gaps should be relatively rare it's still worth doing the book keeping
# that allows us to skip forwards when there are gapless runs of
# positions.
#
# We start at 1 here as a) the first generated stream ID will be 2, and
# b) other parts of the code assume that stream IDs are strictly greater
# than 0.
self._persisted_upto_position = (
min(self._current_positions.values()) if self._current_positions else 0
min(self._current_positions.values()) if self._current_positions else 1
)
self._known_persisted_positions = [] # type: List[int]
@ -362,9 +366,7 @@ class MultiWriterIdGenerator:
equal to it have been successfully persisted.
"""
# Currently we don't support this operation, as it's not obvious how to
# condense the stream positions of multiple writers into a single int.
raise NotImplementedError()
return self.get_persisted_upto_position()
def get_current_token_for_writer(self, instance_name: str) -> int:
"""Returns the position of the given writer.