forked from MirrorHub/synapse
Comments on the /sync tentacles (#11494)
This mainly consists of docstrings and inline comments. There are one or two type annotations and variable renames thrown in while I was here. Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>
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changelog.d/11494.misc
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changelog.d/11494.misc
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@ -0,0 +1 @@
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Add comments to various parts of the `/sync` handler.
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@ -334,6 +334,19 @@ class SyncHandler:
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full_state: bool,
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cache_context: ResponseCacheContext[SyncRequestKey],
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) -> SyncResult:
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"""The start of the machinery that produces a /sync response.
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See https://spec.matrix.org/v1.1/client-server-api/#syncing for full details.
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This method does high-level bookkeeping:
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- tracking the kind of sync in the logging context
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- deleting any to_device messages whose delivery has been acknowledged.
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- deciding if we should dispatch an instant or delayed response
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- marking the sync as being lazily loaded, if appropriate
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Computing the body of the response begins in the next method,
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`current_sync_for_user`.
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"""
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if since_token is None:
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sync_type = "initial_sync"
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elif full_state:
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@ -363,7 +376,7 @@ class SyncHandler:
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sync_config, since_token, full_state=full_state
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)
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else:
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# Otherwise, we wait for something to happen and report it to the user.
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async def current_sync_callback(
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before_token: StreamToken, after_token: StreamToken
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) -> SyncResult:
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@ -402,7 +415,12 @@ class SyncHandler:
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since_token: Optional[StreamToken] = None,
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full_state: bool = False,
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) -> SyncResult:
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"""Get the sync for client needed to match what the server has now."""
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"""Generates the response body of a sync result, represented as a SyncResult.
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This is a wrapper around `generate_sync_result` which starts an open tracing
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span to track the sync. See `generate_sync_result` for the next part of your
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indoctrination.
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"""
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with start_active_span("current_sync_for_user"):
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log_kv({"since_token": since_token})
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sync_result = await self.generate_sync_result(
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@ -560,7 +578,7 @@ class SyncHandler:
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# that have happened since `since_key` up to `end_key`, so we
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# can just use `get_room_events_stream_for_room`.
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# Otherwise, we want to return the last N events in the room
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# in toplogical ordering.
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# in topological ordering.
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if since_key:
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events, end_key = await self.store.get_room_events_stream_for_room(
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room_id,
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@ -1042,7 +1060,18 @@ class SyncHandler:
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since_token: Optional[StreamToken] = None,
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full_state: bool = False,
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) -> SyncResult:
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"""Generates a sync result."""
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"""Generates the response body of a sync result.
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This is represented by a `SyncResult` struct, which is built from small pieces
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using a `SyncResultBuilder`. See also
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https://spec.matrix.org/v1.1/client-server-api/#get_matrixclientv3sync
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the `sync_result_builder` is passed as a mutable ("inout") parameter to various
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helper functions. These retrieve and process the data which forms the sync body,
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often writing to the `sync_result_builder` to store their output.
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At the end, we transfer data from the `sync_result_builder` to a new `SyncResult`
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instance to signify that the sync calculation is complete.
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"""
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# NB: The now_token gets changed by some of the generate_sync_* methods,
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# this is due to some of the underlying streams not supporting the ability
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# to query up to a given point.
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@ -1344,14 +1373,22 @@ class SyncHandler:
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async def _generate_sync_entry_for_account_data(
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self, sync_result_builder: "SyncResultBuilder"
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) -> Dict[str, Dict[str, JsonDict]]:
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"""Generates the account data portion of the sync response. Populates
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`sync_result_builder` with the result.
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"""Generates the account data portion of the sync response.
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Account data (called "Client Config" in the spec) can be set either globally
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or for a specific room. Account data consists of a list of events which
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accumulate state, much like a room.
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This function retrieves global and per-room account data. The former is written
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to the given `sync_result_builder`. The latter is returned directly, to be
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later written to the `sync_result_builder` on a room-by-room basis.
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Args:
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sync_result_builder
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Returns:
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A dictionary containing the per room account data.
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A dictionary whose keys (room ids) map to the per room account data for that
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room.
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"""
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sync_config = sync_result_builder.sync_config
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user_id = sync_result_builder.sync_config.user.to_string()
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@ -1359,7 +1396,7 @@ class SyncHandler:
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if since_token and not sync_result_builder.full_state:
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(
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account_data,
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global_account_data,
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account_data_by_room,
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) = await self.store.get_updated_account_data_for_user(
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user_id, since_token.account_data_key
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@ -1370,23 +1407,23 @@ class SyncHandler:
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)
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if push_rules_changed:
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account_data["m.push_rules"] = await self.push_rules_for_user(
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global_account_data["m.push_rules"] = await self.push_rules_for_user(
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sync_config.user
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)
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else:
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(
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account_data,
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global_account_data,
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account_data_by_room,
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) = await self.store.get_account_data_for_user(sync_config.user.to_string())
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account_data["m.push_rules"] = await self.push_rules_for_user(
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global_account_data["m.push_rules"] = await self.push_rules_for_user(
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sync_config.user
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)
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account_data_for_user = await sync_config.filter_collection.filter_account_data(
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[
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{"type": account_data_type, "content": content}
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for account_data_type, content in account_data.items()
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for account_data_type, content in global_account_data.items()
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]
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)
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@ -1460,15 +1497,22 @@ class SyncHandler:
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"""Generates the rooms portion of the sync response. Populates the
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`sync_result_builder` with the result.
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In the response that reaches the client, rooms are divided into four categories:
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`invite`, `join`, `knock`, `leave`. These aren't the same as the four sets of
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room ids returned by this function.
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Args:
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sync_result_builder
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account_data_by_room: Dictionary of per room account data
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Returns:
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Returns a 4-tuple of
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`(newly_joined_rooms, newly_joined_or_invited_users,
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newly_left_rooms, newly_left_users)`
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Returns a 4-tuple whose entries are:
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- newly_joined_rooms
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- newly_joined_or_invited_or_knocked_users
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- newly_left_rooms
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- newly_left_users
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"""
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# Start by fetching all ephemeral events in rooms we've joined (if required).
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user_id = sync_result_builder.sync_config.user.to_string()
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block_all_room_ephemeral = (
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sync_result_builder.since_token is None
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@ -1590,6 +1634,8 @@ class SyncHandler:
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) -> bool:
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"""Returns whether there may be any new events that should be sent down
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the sync. Returns True if there are.
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Does not modify the `sync_result_builder`.
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"""
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user_id = sync_result_builder.sync_config.user.to_string()
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since_token = sync_result_builder.since_token
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@ -1597,12 +1643,13 @@ class SyncHandler:
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assert since_token
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# Get a list of membership change events that have happened.
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rooms_changed = await self.store.get_membership_changes_for_user(
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# Get a list of membership change events that have happened to the user
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# requesting the sync.
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membership_changes = await self.store.get_membership_changes_for_user(
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user_id, since_token.room_key, now_token.room_key
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)
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if rooms_changed:
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if membership_changes:
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return True
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stream_id = since_token.room_key.stream
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@ -1614,7 +1661,25 @@ class SyncHandler:
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async def _get_rooms_changed(
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self, sync_result_builder: "SyncResultBuilder", ignored_users: FrozenSet[str]
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) -> _RoomChanges:
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"""Gets the the changes that have happened since the last sync."""
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"""Determine the changes in rooms to report to the user.
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Ideally, we want to report all events whose stream ordering `s` lies in the
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range `since_token < s <= now_token`, where the two tokens are read from the
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sync_result_builder.
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If there are too many events in that range to report, things get complicated.
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In this situation we return a truncated list of the most recent events, and
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indicate in the response that there is a "gap" of omitted events. Additionally:
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- we include a "state_delta", to describe the changes in state over the gap,
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- we include all membership events applying to the user making the request,
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even those in the gap.
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See the spec for the rationale:
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https://spec.matrix.org/v1.1/client-server-api/#syncing
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The sync_result_builder is not modified by this function.
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"""
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user_id = sync_result_builder.sync_config.user.to_string()
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since_token = sync_result_builder.since_token
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now_token = sync_result_builder.now_token
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@ -1622,21 +1687,36 @@ class SyncHandler:
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assert since_token
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# Get a list of membership change events that have happened.
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rooms_changed = await self.store.get_membership_changes_for_user(
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# The spec
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# https://spec.matrix.org/v1.1/client-server-api/#get_matrixclientv3sync
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# notes that membership events need special consideration:
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#
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# > When a sync is limited, the server MUST return membership events for events
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# > in the gap (between since and the start of the returned timeline), regardless
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# > as to whether or not they are redundant.
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#
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# We fetch such events here, but we only seem to use them for categorising rooms
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# as newly joined, newly left, invited or knocked.
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# TODO: we've already called this function and ran this query in
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# _have_rooms_changed. We could keep the results in memory to avoid a
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# second query, at the cost of more complicated source code.
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membership_change_events = await self.store.get_membership_changes_for_user(
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user_id, since_token.room_key, now_token.room_key
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)
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mem_change_events_by_room_id: Dict[str, List[EventBase]] = {}
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for event in rooms_changed:
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for event in membership_change_events:
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mem_change_events_by_room_id.setdefault(event.room_id, []).append(event)
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newly_joined_rooms = []
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newly_left_rooms = []
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room_entries = []
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invited = []
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knocked = []
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newly_joined_rooms: List[str] = []
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newly_left_rooms: List[str] = []
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room_entries: List[RoomSyncResultBuilder] = []
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invited: List[InvitedSyncResult] = []
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knocked: List[KnockedSyncResult] = []
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for room_id, events in mem_change_events_by_room_id.items():
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# The body of this loop will add this room to at least one of the five lists
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# above. Things get messy if you've e.g. joined, left, joined then left the
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# room all in the same sync period.
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logger.debug(
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"Membership changes in %s: [%s]",
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room_id,
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@ -1781,7 +1861,9 @@ class SyncHandler:
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timeline_limit = sync_config.filter_collection.timeline_limit()
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# Get all events for rooms we're currently joined to.
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# Get all events since the `from_key` in rooms we're currently joined to.
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# If there are too many, we get the most recent events only. This leaves
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# a "gap" in the timeline, as described by the spec for /sync.
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room_to_events = await self.store.get_room_events_stream_for_rooms(
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room_ids=sync_result_builder.joined_room_ids,
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from_key=since_token.room_key,
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) -> _RoomChanges:
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"""Returns entries for all rooms for the user.
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Like `_get_rooms_changed`, but assumes the `since_token` is `None`.
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This function does not modify the sync_result_builder.
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Args:
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sync_result_builder
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ignored_users: Set of users ignored by user.
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@ -1853,16 +1939,9 @@ class SyncHandler:
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now_token = sync_result_builder.now_token
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sync_config = sync_result_builder.sync_config
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membership_list = (
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Membership.INVITE,
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Membership.KNOCK,
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Membership.JOIN,
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Membership.LEAVE,
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Membership.BAN,
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)
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room_list = await self.store.get_rooms_for_local_user_where_membership_is(
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user_id=user_id, membership_list=membership_list
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user_id=user_id,
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membership_list=Membership.LIST,
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)
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room_entries = []
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# to only include membership events for the senders in the timeline.
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# In practice, we can do this by removing them from the p_ids list,
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# which is the list of relevant state we know we have already sent to the client.
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# see https://github.com/matrix-org/synapse/pull/2970
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# /files/efcdacad7d1b7f52f879179701c7e0d9b763511f#r204732809
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# see https://github.com/matrix-org/synapse/pull/2970/files/efcdacad7d1b7f52f879179701c7e0d9b763511f#r204732809
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if lazy_load_members:
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p_ids.difference_update(
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@ -497,7 +497,7 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore, metaclass=abc.ABCMeta):
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oldest `limit` events.
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Returns:
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The list of events (in ascending order) and the token from the start
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The list of events (in ascending stream order) and the token from the start
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of the chunk of events returned.
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"""
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if from_key == to_key:
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@ -510,7 +510,7 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore, metaclass=abc.ABCMeta):
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if not has_changed:
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return [], from_key
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def f(txn):
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def f(txn: LoggingTransaction) -> List[_EventDictReturn]:
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# To handle tokens with a non-empty instance_map we fetch more
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# results than necessary and then filter down
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min_from_id = from_key.stream
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@ -565,6 +565,13 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore, metaclass=abc.ABCMeta):
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async def get_membership_changes_for_user(
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self, user_id: str, from_key: RoomStreamToken, to_key: RoomStreamToken
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) -> List[EventBase]:
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"""Fetch membership events for a given user.
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All such events whose stream ordering `s` lies in the range
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`from_key < s <= to_key` are returned. Events are ordered by ascending stream
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order.
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"""
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# Start by ruling out cases where a DB query is not necessary.
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if from_key == to_key:
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return []
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if not has_changed:
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return []
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def f(txn):
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def f(txn: LoggingTransaction) -> List[_EventDictReturn]:
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# To handle tokens with a non-empty instance_map we fetch more
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# results than necessary and then filter down
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min_from_id = from_key.stream
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Returns:
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A list of events and a token pointing to the start of the returned
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events. The events returned are in ascending order.
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events. The events returned are in ascending topological order.
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"""
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rows, token = await self.get_recent_event_ids_for_room(
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