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forked-synapse/synapse/events/snapshot.py
Shay 03bccd542b
Add a class UnpersistedEventContext to allow for the batching up of storing state groups (#14675) 
* add class UnpersistedEventContext

* modify create new client event to create unpersistedeventcontexts

* persist event contexts after creation

* fix tests to persist unpersisted event contexts

* cleanup

* misc lints + cleanup

* changelog + fix comments

* lints

* fix batch insertion?

* reduce redundant calculation

* add unpersisted event classes

* rework compute_event_context, split into function that returns unpersisted event context and then persists it

* use calculate_context_info to create unpersisted event contexts

* update typing

* $%#^&*

* black

* fix comments and consolidate classes, use attr.s for class

* requested changes

* lint

* requested changes

* requested changes

* refactor to be stupidly explicit

* clearer renaming and flow

* make partial state non-optional

* update docstrings

---------

Co-authored-by: Erik Johnston <erik@matrix.org>
2023-02-09 13:05:02 -08:00

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# Copyright 2014-2016 OpenMarket 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.
from abc import ABC, abstractmethod
from typing import TYPE_CHECKING, List, Optional, Tuple
import attr
from frozendict import frozendict
from synapse.appservice import ApplicationService
from synapse.events import EventBase
from synapse.types import JsonDict, StateMap
if TYPE_CHECKING:
from synapse.storage.controllers import StorageControllers
from synapse.storage.databases.main import DataStore
from synapse.types.state import StateFilter
class UnpersistedEventContextBase(ABC):
"""
This is a base class for EventContext and UnpersistedEventContext, objects which
hold information relevant to storing an associated event. Note that an
UnpersistedEventContexts must be converted into an EventContext before it is
suitable to send to the db with its associated event.
Attributes:
_storage: storage controllers for interfacing with the database
app_service: If the associated event is being sent by a (local) application service, that
app service.
"""
def __init__(self, storage_controller: "StorageControllers"):
self._storage: "StorageControllers" = storage_controller
self.app_service: Optional[ApplicationService] = None
@abstractmethod
async def persist(
self,
event: EventBase,
) -> "EventContext":
"""
A method to convert an UnpersistedEventContext to an EventContext, suitable for
sending to the database with the associated event.
"""
pass
@abstractmethod
async def get_prev_state_ids(
self, state_filter: Optional["StateFilter"] = None
) -> StateMap[str]:
"""
Gets the room state at the event (ie not including the event if the event is a
state event).
Args:
state_filter: specifies the type of state event to fetch from DB, example:
EventTypes.JoinRules
"""
pass
@attr.s(slots=True, auto_attribs=True)
class EventContext(UnpersistedEventContextBase):
"""
Holds information relevant to persisting an event
Attributes:
rejected: A rejection reason if the event was rejected, else None
_state_group: The ID of the state group for this event. Note that state events
are persisted with a state group which includes the new event, so this is
effectively the state *after* the event in question.
For a *rejected* state event, where the state of the rejected event is
ignored, this state_group should never make it into the
event_to_state_groups table. Indeed, inspecting this value for a rejected
state event is almost certainly incorrect.
For an outlier, where we don't have the state at the event, this will be
None.
Note that this is a private attribute: it should be accessed via
the ``state_group`` property.
state_group_before_event: The ID of the state group representing the state
of the room before this event.
If this is a non-state event, this will be the same as ``state_group``. If
it's a state event, it will be the same as ``prev_group``.
If ``state_group`` is None (ie, the event is an outlier),
``state_group_before_event`` will always also be ``None``.
state_delta_due_to_event: If `state_group` and `state_group_before_event` are not None
then this is the delta of the state between the two groups.
prev_group: If it is known, ``state_group``'s prev_group. Note that this being
None does not necessarily mean that ``state_group`` does not have
a prev_group!
If the event is a state event, this is normally the same as
``state_group_before_event``.
If ``state_group`` is None (ie, the event is an outlier), ``prev_group``
will always also be ``None``.
Note that this *not* (necessarily) the state group associated with
``_prev_state_ids``.
delta_ids: If ``prev_group`` is not None, the state delta between ``prev_group``
and ``state_group``.
partial_state: if True, we may be storing this event with a temporary,
incomplete state.
"""
_storage: "StorageControllers"
rejected: Optional[str] = None
_state_group: Optional[int] = None
state_group_before_event: Optional[int] = None
_state_delta_due_to_event: Optional[StateMap[str]] = None
prev_group: Optional[int] = None
delta_ids: Optional[StateMap[str]] = None
app_service: Optional[ApplicationService] = None
partial_state: bool = False
@staticmethod
def with_state(
storage: "StorageControllers",
state_group: Optional[int],
state_group_before_event: Optional[int],
state_delta_due_to_event: Optional[StateMap[str]],
partial_state: bool,
prev_group: Optional[int] = None,
delta_ids: Optional[StateMap[str]] = None,
) -> "EventContext":
return EventContext(
storage=storage,
state_group=state_group,
state_group_before_event=state_group_before_event,
state_delta_due_to_event=state_delta_due_to_event,
prev_group=prev_group,
delta_ids=delta_ids,
partial_state=partial_state,
)
@staticmethod
def for_outlier(
storage: "StorageControllers",
) -> "EventContext":
"""Return an EventContext instance suitable for persisting an outlier event"""
return EventContext(storage=storage)
async def persist(self, event: EventBase) -> "EventContext":
return self
async def serialize(self, event: EventBase, store: "DataStore") -> JsonDict:
"""Converts self to a type that can be serialized as JSON, and then
deserialized by `deserialize`
Args:
event: The event that this context relates to
Returns:
The serialized event.
"""
return {
"state_group": self._state_group,
"state_group_before_event": self.state_group_before_event,
"rejected": self.rejected,
"prev_group": self.prev_group,
"state_delta_due_to_event": _encode_state_dict(
self._state_delta_due_to_event
),
"delta_ids": _encode_state_dict(self.delta_ids),
"app_service_id": self.app_service.id if self.app_service else None,
"partial_state": self.partial_state,
}
@staticmethod
def deserialize(storage: "StorageControllers", input: JsonDict) -> "EventContext":
"""Converts a dict that was produced by `serialize` back into a
EventContext.
Args:
storage: Used to convert AS ID to AS object and fetch state.
input: A dict produced by `serialize`
Returns:
The event context.
"""
context = EventContext(
# We use the state_group and prev_state_id stuff to pull the
# current_state_ids out of the DB and construct prev_state_ids.
storage=storage,
state_group=input["state_group"],
state_group_before_event=input["state_group_before_event"],
prev_group=input["prev_group"],
state_delta_due_to_event=_decode_state_dict(
input["state_delta_due_to_event"]
),
delta_ids=_decode_state_dict(input["delta_ids"]),
rejected=input["rejected"],
partial_state=input.get("partial_state", False),
)
app_service_id = input["app_service_id"]
if app_service_id:
context.app_service = storage.main.get_app_service_by_id(app_service_id)
return context
@property
def state_group(self) -> Optional[int]:
"""The ID of the state group for this event.
Note that state events are persisted with a state group which includes the new
event, so this is effectively the state *after* the event in question.
For an outlier, where we don't have the state at the event, this will be None.
It is an error to access this for a rejected event, since rejected state should
not make it into the room state. Accessing this property will raise an exception
if ``rejected`` is set.
"""
if self.rejected:
raise RuntimeError("Attempt to access state_group of rejected event")
return self._state_group
async def get_current_state_ids(
self, state_filter: Optional["StateFilter"] = None
) -> Optional[StateMap[str]]:
"""
Gets the room state map, including this event - ie, the state in ``state_group``
It is an error to access this for a rejected event, since rejected state should
not make it into the room state. This method will raise an exception if
``rejected`` is set.
Arg:
state_filter: specifies the type of state event to fetch from DB, example: EventTypes.JoinRules
Returns:
Returns None if state_group is None, which happens when the associated
event is an outlier.
Maps a (type, state_key) to the event ID of the state event matching
this tuple.
"""
if self.rejected:
raise RuntimeError("Attempt to access state_ids of rejected event")
assert self._state_delta_due_to_event is not None
prev_state_ids = await self.get_prev_state_ids(state_filter)
if self._state_delta_due_to_event:
prev_state_ids = dict(prev_state_ids)
prev_state_ids.update(self._state_delta_due_to_event)
return prev_state_ids
async def get_prev_state_ids(
self, state_filter: Optional["StateFilter"] = None
) -> StateMap[str]:
"""
Gets the room state map, excluding this event.
For a non-state event, this will be the same as get_current_state_ids().
Args:
state_filter: specifies the type of state event to fetch from DB, example: EventTypes.JoinRules
Returns:
Returns {} if state_group is None, which happens when the associated
event is an outlier.
Maps a (type, state_key) to the event ID of the state event matching
this tuple.
"""
assert self.state_group_before_event is not None
return await self._storage.state.get_state_ids_for_group(
self.state_group_before_event, state_filter
)
@attr.s(slots=True, auto_attribs=True)
class UnpersistedEventContext(UnpersistedEventContextBase):
"""
The event context holds information about the state groups for an event. It is important
to remember that an event technically has two state groups: the state group before the
event, and the state group after the event. If the event is not a state event, the state
group will not change (ie the state group before the event will be the same as the state
group after the event), but if it is a state event the state group before the event
will differ from the state group after the event.
This is a version of an EventContext before the new state group (if any) has been
computed and stored. It contains information about the state before the event (which
also may be the information after the event, if the event is not a state event). The
UnpersistedEventContext must be converted into an EventContext by calling the method
'persist' on it before it is suitable to be sent to the DB for processing.
state_group_after_event:
The state group after the event. This will always be None until it is persisted.
If the event is not a state event, this will be the same as
state_group_before_event.
state_group_before_event:
The ID of the state group representing the state of the room before this event.
state_delta_due_to_event:
If the event is a state event, then this is the delta of the state between
`state_group` and `state_group_before_event`
prev_group_for_state_group_before_event:
If it is known, ``state_group_before_event``'s previous state group.
delta_ids_to_state_group_before_event:
If ``prev_group_for_state_group_before_event`` is not None, the state delta
between ``prev_group_for_state_group_before_event`` and ``state_group_before_event``.
partial_state:
Whether the event has partial state.
state_map_before_event:
A map of the state before the event, i.e. the state at `state_group_before_event`
"""
_storage: "StorageControllers"
state_group_before_event: Optional[int]
state_group_after_event: Optional[int]
state_delta_due_to_event: Optional[dict]
prev_group_for_state_group_before_event: Optional[int]
delta_ids_to_state_group_before_event: Optional[StateMap[str]]
partial_state: bool
state_map_before_event: Optional[StateMap[str]] = None
async def get_prev_state_ids(
self, state_filter: Optional["StateFilter"] = None
) -> StateMap[str]:
"""
Gets the room state map, excluding this event.
Args:
state_filter: specifies the type of state event to fetch from DB
Returns:
Maps a (type, state_key) to the event ID of the state event matching
this tuple.
"""
if self.state_map_before_event:
return self.state_map_before_event
assert self.state_group_before_event is not None
return await self._storage.state.get_state_ids_for_group(
self.state_group_before_event, state_filter
)
async def persist(self, event: EventBase) -> EventContext:
"""
Creates a full `EventContext` for the event, persisting any referenced state that
has not yet been persisted.
Args:
event: event that the EventContext is associated with.
Returns: An EventContext suitable for sending to the database with the event
for persisting
"""
assert self.partial_state is not None
# If we have a full set of state for before the event but don't have a state
# group for that state, we need to get one
if self.state_group_before_event is None:
assert self.state_map_before_event
state_group_before_event = await self._storage.state.store_state_group(
event.event_id,
event.room_id,
prev_group=self.prev_group_for_state_group_before_event,
delta_ids=self.delta_ids_to_state_group_before_event,
current_state_ids=self.state_map_before_event,
)
self.state_group_before_event = state_group_before_event
# if the event isn't a state event the state group doesn't change
if not self.state_delta_due_to_event:
state_group_after_event = self.state_group_before_event
# otherwise if it is a state event we need to get a state group for it
else:
state_group_after_event = await self._storage.state.store_state_group(
event.event_id,
event.room_id,
prev_group=self.state_group_before_event,
delta_ids=self.state_delta_due_to_event,
current_state_ids=None,
)
return EventContext.with_state(
storage=self._storage,
state_group=state_group_after_event,
state_group_before_event=self.state_group_before_event,
state_delta_due_to_event=self.state_delta_due_to_event,
partial_state=self.partial_state,
prev_group=self.state_group_before_event,
delta_ids=self.state_delta_due_to_event,
)
def _encode_state_dict(
state_dict: Optional[StateMap[str]],
) -> Optional[List[Tuple[str, str, str]]]:
"""Since dicts of (type, state_key) -> event_id cannot be serialized in
JSON we need to convert them to a form that can.
"""
if state_dict is None:
return None
return [(etype, state_key, v) for (etype, state_key), v in state_dict.items()]
def _decode_state_dict(
input: Optional[List[Tuple[str, str, str]]]
) -> Optional[StateMap[str]]:
"""Decodes a state dict encoded using `_encode_state_dict` above"""
if input is None:
return None
return frozendict({(etype, state_key): v for etype, state_key, v in input})
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