Add endpoints for backfilling history (MSC2716) (#9247)

Work on matrix-org/matrix-spec-proposals#2716

Author: MadLittleMods

changelog.d/9247.feature

@@ -0,0 +1 @@
+Add experimental support for backfilling history into rooms ([MSC2716](https://github.com/matrix-org/matrix-doc/pull/2716)).

scripts-dev/complement.sh

@@ -65,4 +65,4 @@ if [[ -n "$1" ]]; then
 fi
 
 # Run the tests!
-go test -v -tags synapse_blacklist,msc2946,msc3083 -count=1 $EXTRA_COMPLEMENT_ARGS ./tests
+go test -v -tags synapse_blacklist,msc2946,msc3083,msc2716 -count=1 $EXTRA_COMPLEMENT_ARGS ./tests

synapse/api/auth.py

@@ -92,11 +92,8 @@ def __init__(self, hs: "HomeServer"):
     async def check_from_context(
         self, room_version: str, event, context, do_sig_check=True
     ) -> None:
-        prev_state_ids = await context.get_prev_state_ids()
-        auth_events_ids = self.compute_auth_events(
-            event, prev_state_ids, for_verification=True
-        )
-        auth_events_by_id = await self.store.get_events(auth_events_ids)
+        auth_event_ids = event.auth_event_ids()
+        auth_events_by_id = await self.store.get_events(auth_event_ids)
         auth_events = {(e.type, e.state_key): e for e in auth_events_by_id.values()}
 
         room_version_obj = KNOWN_ROOM_VERSIONS[room_version]

synapse/api/constants.py

@@ -119,6 +119,9 @@ class EventTypes:
     SpaceChild = "m.space.child"
     SpaceParent = "m.space.parent"
 
+    MSC2716_INSERTION = "org.matrix.msc2716.insertion"
+    MSC2716_MARKER = "org.matrix.msc2716.marker"
+
 
 class ToDeviceEventTypes:
     RoomKeyRequest = "m.room_key_request"
@@ -185,6 +188,18 @@ class EventContentFields:
     # cf https://github.com/matrix-org/matrix-doc/pull/1772
     ROOM_TYPE = "type"
 
+    # Used on normal messages to indicate they were historically imported after the fact
+    MSC2716_HISTORICAL = "org.matrix.msc2716.historical"
+    # For "insertion" events
+    MSC2716_NEXT_CHUNK_ID = "org.matrix.msc2716.next_chunk_id"
+    # Used on normal message events to indicate where the chunk connects to
+    MSC2716_CHUNK_ID = "org.matrix.msc2716.chunk_id"
+    # For "marker" events
+    MSC2716_MARKER_INSERTION = "org.matrix.msc2716.marker.insertion"
+    MSC2716_MARKER_INSERTION_PREV_EVENTS = (
+        "org.matrix.msc2716.marker.insertion_prev_events"
+    )
+
 
 class RoomEncryptionAlgorithms:
     MEGOLM_V1_AES_SHA2 = "m.megolm.v1.aes-sha2"

synapse/config/experimental.py

@@ -29,3 +29,6 @@ def read_config(self, config: JsonDict, **kwargs):
 
         # MSC3026 (busy presence state)
         self.msc3026_enabled = experimental.get("msc3026_enabled", False)  # type: bool
+
+        # MSC2716 (backfill existing history)
+        self.msc2716_enabled = experimental.get("msc2716_enabled", False)  # type: bool

synapse/events/__init__.py

@@ -119,6 +119,7 @@ def __init__(self, internal_metadata_dict: JsonDict):
     redacted = DictProperty("redacted")  # type: bool
     txn_id = DictProperty("txn_id")  # type: str
     token_id = DictProperty("token_id")  # type: str
+    historical = DictProperty("historical")  # type: bool
 
     # XXX: These are set by StreamWorkerStore._set_before_and_after.
     # I'm pretty sure that these are never persisted to the database, so shouldn't
@@ -204,6 +205,14 @@ def is_redacted(self):
         """
         return self._dict.get("redacted", False)
 
+    def is_historical(self) -> bool:
+        """Whether this is a historical message.
+        This is used by the batchsend historical message endpoint and
+        is needed to and mark the event as backfilled and skip some checks
+        like push notifications.
+        """
+        return self._dict.get("historical", False)
+
 
 class EventBase(metaclass=abc.ABCMeta):
     @property

synapse/events/builder.py

@@ -11,6 +11,7 @@
 # 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.
+import logging
 from typing import Any, Dict, List, Optional, Tuple, Union
 
 import attr
@@ -33,6 +34,8 @@
 from synapse.util import Clock
 from synapse.util.stringutils import random_string
 
+logger = logging.getLogger(__name__)
+
 
 @attr.s(slots=True, cmp=False, frozen=True)
 class EventBuilder:
@@ -100,6 +103,7 @@ async def build(
         self,
         prev_event_ids: List[str],
         auth_event_ids: Optional[List[str]],
+        depth: Optional[int] = None,
     ) -> EventBase:
         """Transform into a fully signed and hashed event
 
@@ -108,6 +112,9 @@ async def build(
             auth_event_ids: The event IDs to use as the auth events.
                 Should normally be set to None, which will cause them to be calculated
                 based on the room state at the prev_events.
+            depth: Override the depth used to order the event in the DAG.
+                Should normally be set to None, which will cause the depth to be calculated
+                based on the prev_events.
 
         Returns:
             The signed and hashed event.
@@ -131,8 +138,14 @@ async def build(
             auth_events = auth_event_ids
             prev_events = prev_event_ids
 
-        old_depth = await self._store.get_max_depth_of(prev_event_ids)
-        depth = old_depth + 1
+        # Otherwise, progress the depth as normal
+        if depth is None:
+            (
+                _,
+                most_recent_prev_event_depth,
+            ) = await self._store.get_max_depth_of(prev_event_ids)
+
+            depth = most_recent_prev_event_depth + 1
 
         # we cap depth of generated events, to ensure that they are not
         # rejected by other servers (and so that they can be persisted in

synapse/handlers/message.py

@@ -482,6 +482,9 @@ async def create_event(
         prev_event_ids: Optional[List[str]] = None,
         auth_event_ids: Optional[List[str]] = None,
         require_consent: bool = True,
+        outlier: bool = False,
+        historical: bool = False,
+        depth: Optional[int] = None,
     ) -> Tuple[EventBase, EventContext]:
         """
         Given a dict from a client, create a new event.
@@ -508,6 +511,14 @@ async def create_event(
 
             require_consent: Whether to check if the requester has
                 consented to the privacy policy.
+
+            outlier: Indicates whether the event is an `outlier`, i.e. if
+                it's from an arbitrary point and floating in the DAG as
+                opposed to being inline with the current DAG.
+            depth: Override the depth used to order the event in the DAG.
+                Should normally be set to None, which will cause the depth to be calculated
+                based on the prev_events.
+
         Raises:
             ResourceLimitError if server is blocked to some resource being
             exceeded
@@ -563,11 +574,36 @@ async def create_event(
         if txn_id is not None:
             builder.internal_metadata.txn_id = txn_id
 
+        builder.internal_metadata.outlier = outlier
+
+        builder.internal_metadata.historical = historical
+
+        # Strip down the auth_event_ids to only what we need to auth the event.
+        # For example, we don't need extra m.room.member that don't match event.sender
+        if auth_event_ids is not None:
+            temp_event = await builder.build(
+                prev_event_ids=prev_event_ids,
+                auth_event_ids=auth_event_ids,
+                depth=depth,
+            )
+            auth_events = await self.store.get_events_as_list(auth_event_ids)
+            # Create a StateMap[str]
+            auth_event_state_map = {
+                (e.type, e.state_key): e.event_id for e in auth_events
+            }
+            # Actually strip down and use the necessary auth events
+            auth_event_ids = self.auth.compute_auth_events(
+                event=temp_event,
+                current_state_ids=auth_event_state_map,
+                for_verification=False,
+            )
+
         event, context = await self.create_new_client_event(
             builder=builder,
             requester=requester,
             prev_event_ids=prev_event_ids,
             auth_event_ids=auth_event_ids,
+            depth=depth,
         )
 
         # In an ideal world we wouldn't need the second part of this condition. However,
@@ -724,9 +760,13 @@ async def create_and_send_nonmember_event(
         self,
         requester: Requester,
         event_dict: dict,
+        prev_event_ids: Optional[List[str]] = None,
+        auth_event_ids: Optional[List[str]] = None,
         ratelimit: bool = True,
         txn_id: Optional[str] = None,
         ignore_shadow_ban: bool = False,
+        outlier: bool = False,
+        depth: Optional[int] = None,
     ) -> Tuple[EventBase, int]:
         """
         Creates an event, then sends it.
@@ -736,10 +776,24 @@ async def create_and_send_nonmember_event(
         Args:
             requester: The requester sending the event.
             event_dict: An entire event.
+            prev_event_ids:
+                The event IDs to use as the prev events.
+                Should normally be left as None to automatically request them
+                from the database.
+            auth_event_ids:
+                The event ids to use as the auth_events for the new event.
+                Should normally be left as None, which will cause them to be calculated
+                based on the room state at the prev_events.
             ratelimit: Whether to rate limit this send.
             txn_id: The transaction ID.
             ignore_shadow_ban: True if shadow-banned users should be allowed to
                 send this event.
+            outlier: Indicates whether the event is an `outlier`, i.e. if
+                it's from an arbitrary point and floating in the DAG as
+                opposed to being inline with the current DAG.
+            depth: Override the depth used to order the event in the DAG.
+                Should normally be set to None, which will cause the depth to be calculated
+                based on the prev_events.
 
         Returns:
             The event, and its stream ordering (if deduplication happened,
@@ -779,7 +833,13 @@ async def create_and_send_nonmember_event(
                     return event, event.internal_metadata.stream_ordering
 
             event, context = await self.create_event(
-                requester, event_dict, txn_id=txn_id
+                requester,
+                event_dict,
+                txn_id=txn_id,
+                prev_event_ids=prev_event_ids,
+                auth_event_ids=auth_event_ids,
+                outlier=outlier,
+                depth=depth,
             )
 
             assert self.hs.is_mine_id(event.sender), "User must be our own: %s" % (
@@ -811,6 +871,7 @@ async def create_new_client_event(
         requester: Optional[Requester] = None,
         prev_event_ids: Optional[List[str]] = None,
         auth_event_ids: Optional[List[str]] = None,
+        depth: Optional[int] = None,
     ) -> Tuple[EventBase, EventContext]:
         """Create a new event for a local client
 
@@ -828,6 +889,10 @@ async def create_new_client_event(
                 Should normally be left as None, which will cause them to be calculated
                 based on the room state at the prev_events.
 
+            depth: Override the depth used to order the event in the DAG.
+                Should normally be set to None, which will cause the depth to be calculated
+                based on the prev_events.
+
         Returns:
             Tuple of created event, context
         """
@@ -851,9 +916,24 @@ async def create_new_client_event(
         ), "Attempting to create an event with no prev_events"
 
         event = await builder.build(
-            prev_event_ids=prev_event_ids, auth_event_ids=auth_event_ids
+            prev_event_ids=prev_event_ids,
+            auth_event_ids=auth_event_ids,
+            depth=depth,
         )
-        context = await self.state.compute_event_context(event)
+
+        old_state = None
+
+        # Pass on the outlier property from the builder to the event
+        # after it is created
+        if builder.internal_metadata.outlier:
+            event.internal_metadata.outlier = builder.internal_metadata.outlier
+
+            # Calculate the state for outliers that pass in their own `auth_event_ids`
+            if auth_event_ids:
+                old_state = await self.store.get_events_as_list(auth_event_ids)
+
+        context = await self.state.compute_event_context(event, old_state=old_state)
+
         if requester:
             context.app_service = requester.app_service
 
@@ -1018,7 +1098,13 @@ async def _persist_event(
         the arguments.
         """
 
-        await self.action_generator.handle_push_actions_for_event(event, context)
+        # Skip push notification actions for historical messages
+        # because we don't want to notify people about old history back in time.
+        # The historical messages also do not have the proper `context.current_state_ids`
+        # and `state_groups` because they have `prev_events` that aren't persisted yet
+        # (historical messages persisted in reverse-chronological order).
+        if not event.internal_metadata.is_historical():
+            await self.action_generator.handle_push_actions_for_event(event, context)
 
         try:
             # If we're a worker we need to hit out to the master.
@@ -1317,13 +1403,21 @@ async def persist_and_notify_client_event(
             if prev_state_ids:
                 raise AuthError(403, "Changing the room create event is forbidden")
 
+        # Mark any `m.historical` messages as backfilled so they don't appear
+        # in `/sync` and have the proper decrementing `stream_ordering` as we import
+        backfilled = False
+        if event.internal_metadata.is_historical():
+            backfilled = True
+
         # Note that this returns the event that was persisted, which may not be
         # the same as we passed in if it was deduplicated due transaction IDs.
         (
             event,
             event_pos,
             max_stream_token,
-        ) = await self.storage.persistence.persist_event(event, context=context)
+        ) = await self.storage.persistence.persist_event(
+            event, context=context, backfilled=backfilled
+        )
 
         if self._ephemeral_events_enabled:
             # If there's an expiry timestamp on the event, schedule its expiry.