Use a new token format for sliding sync (#17452)

This is in preparation for adding per-connection state.

---------

Co-authored-by: Eric Eastwood <eric.eastwood@beta.gouv.fr>

4 files changed, 75 insertions, 17 deletions

diff --git a/synapse/handlers/sliding_sync.py b/synapse/handlers/sliding_sync.py
index 554ab59bf3..36665db8e1 100644
--- a/synapse/handlers/sliding_sync.py
+++ b/synapse/handlers/sliding_sync.py
@@ -49,6 +49,7 @@ from synapse.types import (
     PersistedEventPosition,
     Requester,
     RoomStreamToken,
+    SlidingSyncStreamToken,
     StateMap,
     StreamKeyType,
     StreamToken,
@@ -362,7 +363,7 @@ class SlidingSyncHandler:
         self,
         requester: Requester,
         sync_config: SlidingSyncConfig,
-        from_token: Optional[StreamToken] = None,
+        from_token: Optional[SlidingSyncStreamToken] = None,
         timeout_ms: int = 0,
     ) -> SlidingSyncResult:
         """
@@ -393,7 +394,7 @@ class SlidingSyncHandler:
             # this returns false, it means we timed out waiting, and we should
             # just return an empty response.
             before_wait_ts = self.clock.time_msec()
-            if not await self.notifier.wait_for_stream_token(from_token):
+            if not await self.notifier.wait_for_stream_token(from_token.stream_token):
                 logger.warning(
                     "Timed out waiting for worker to catch up. Returning empty response"
                 )
@@ -431,7 +432,7 @@ class SlidingSyncHandler:
                 sync_config.user.to_string(),
                 timeout_ms,
                 current_sync_callback,
-                from_token=from_token,
+                from_token=from_token.stream_token,
             )
 
         return result
@@ -440,7 +441,7 @@ class SlidingSyncHandler:
         self,
         sync_config: SlidingSyncConfig,
         to_token: StreamToken,
-        from_token: Optional[StreamToken] = None,
+        from_token: Optional[SlidingSyncStreamToken] = None,
     ) -> SlidingSyncResult:
         """
         Generates the response body of a Sliding Sync result, represented as a
@@ -473,7 +474,7 @@ class SlidingSyncHandler:
                 await self.get_room_membership_for_user_at_to_token(
                     user=sync_config.user,
                     to_token=to_token,
-                    from_token=from_token,
+                    from_token=from_token.stream_token if from_token else None,
                 )
             )
 
@@ -631,8 +632,11 @@ class SlidingSyncHandler:
             to_token=to_token,
         )
 
+        # TODO: Update this when we implement per-connection state
+        connection_token = 0
+
         return SlidingSyncResult(
-            next_pos=to_token,
+            next_pos=SlidingSyncStreamToken(to_token, connection_token),
             lists=lists,
             rooms=rooms,
             extensions=extensions,
@@ -1367,7 +1371,7 @@ class SlidingSyncHandler:
         room_id: str,
         room_sync_config: RoomSyncConfig,
         room_membership_for_user_at_to_token: _RoomMembershipForUser,
-        from_token: Optional[StreamToken],
+        from_token: Optional[SlidingSyncStreamToken],
         to_token: StreamToken,
     ) -> SlidingSyncResult.RoomResult:
         """
@@ -1431,7 +1435,7 @@ class SlidingSyncHandler:
             #  - TODO: For an incremental sync where we haven't sent it down this
             #    connection before
             to_bound = (
-                from_token.room_key
+                from_token.stream_token.room_key
                 if from_token is not None
                 and not room_membership_for_user_at_to_token.newly_joined
                 else None
@@ -1498,7 +1502,9 @@ class SlidingSyncHandler:
                         instance_name=timeline_event.internal_metadata.instance_name,
                         stream=timeline_event.internal_metadata.stream_ordering,
                     )
-                    if persisted_position.persisted_after(from_token.room_key):
+                    if persisted_position.persisted_after(
+                        from_token.stream_token.room_key
+                    ):
                         num_live += 1
                     else:
                         # Since we're iterating over the timeline events in
@@ -1786,7 +1792,7 @@ class SlidingSyncHandler:
         self,
         sync_config: SlidingSyncConfig,
         to_token: StreamToken,
-        from_token: Optional[StreamToken],
+        from_token: Optional[SlidingSyncStreamToken],
     ) -> SlidingSyncResult.Extensions:
         """Handle extension requests.
 
@@ -1900,7 +1906,7 @@ class SlidingSyncHandler:
         sync_config: SlidingSyncConfig,
         e2ee_request: SlidingSyncConfig.Extensions.E2eeExtension,
         to_token: StreamToken,
-        from_token: Optional[StreamToken],
+        from_token: Optional[SlidingSyncStreamToken],
     ) -> Optional[SlidingSyncResult.Extensions.E2eeExtension]:
         """Handle E2EE device extension (MSC3884)
 
@@ -1922,7 +1928,7 @@ class SlidingSyncHandler:
             # TODO: This should take into account the `from_token` and `to_token`
             device_list_updates = await self.device_handler.get_user_ids_changed(
                 user_id=user_id,
-                from_token=from_token,
+                from_token=from_token.stream_token,
             )
 
         device_one_time_keys_count: Mapping[str, int] = {}
diff --git a/synapse/rest/client/sync.py b/synapse/rest/client/sync.py
index 93fe1d439e..d72dfa2b10 100644
--- a/synapse/rest/client/sync.py
+++ b/synapse/rest/client/sync.py
@@ -54,7 +54,7 @@ from synapse.http.servlet import (
 from synapse.http.site import SynapseRequest
 from synapse.logging.opentracing import trace_with_opname
 from synapse.rest.admin.experimental_features import ExperimentalFeature
-from synapse.types import JsonDict, Requester, StreamToken
+from synapse.types import JsonDict, Requester, SlidingSyncStreamToken, StreamToken
 from synapse.types.rest.client import SlidingSyncBody
 from synapse.util import json_decoder
 from synapse.util.caches.lrucache import LruCache
@@ -889,7 +889,9 @@ class SlidingSyncRestServlet(RestServlet):
 
         from_token = None
         if from_token_string is not None:
-            from_token = await StreamToken.from_string(self.store, from_token_string)
+            from_token = await SlidingSyncStreamToken.from_string(
+                self.store, from_token_string
+            )
 
         # TODO: We currently don't know whether we're going to use sticky params or
         # maybe some filters like sync v2  where they are built up once and referenced
diff --git a/synapse/types/__init__.py b/synapse/types/__init__.py
index c0d30ac2a3..5259550f1c 100644
--- a/synapse/types/__init__.py
+++ b/synapse/types/__init__.py
@@ -1161,6 +1161,49 @@ StreamToken.START = StreamToken(
 
 
 @attr.s(slots=True, frozen=True, auto_attribs=True)
+class SlidingSyncStreamToken:
+    """The same as a `StreamToken`, but includes an extra field at the start for
+    the sliding sync connection token (separated by a '/'). This is used to
+    store per-connection state.
+
+    This then looks something like:
+        5/s2633508_17_338_6732159_1082514_541479_274711_265584_1_379
+
+    Attributes:
+        stream_token: Token representing the position of all the standard
+            streams.
+        connection_position: Token used by sliding sync to track updates to any
+            per-connection state stored by Synapse.
+    """
+
+    stream_token: StreamToken
+    connection_position: int
+
+    @staticmethod
+    @cancellable
+    async def from_string(store: "DataStore", string: str) -> "SlidingSyncStreamToken":
+        """Creates a SlidingSyncStreamToken from its textual representation."""
+        try:
+            connection_position_str, stream_token_str = string.split("/", 1)
+            connection_position = int(connection_position_str)
+            stream_token = await StreamToken.from_string(store, stream_token_str)
+
+            return SlidingSyncStreamToken(
+                stream_token=stream_token,
+                connection_position=connection_position,
+            )
+        except CancelledError:
+            raise
+        except Exception:
+            raise SynapseError(400, "Invalid stream token")
+
+    async def to_string(self, store: "DataStore") -> str:
+        """Serializes the token to a string"""
+        stream_token_str = await self.stream_token.to_string(store)
+        return f"{self.connection_position}/{stream_token_str}"
+
+
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class PersistedPosition:
     """Position of a newly persisted row with instance that persisted it."""
 
diff --git a/synapse/types/handlers/__init__.py b/synapse/types/handlers/__init__.py
index 4c6c42db04..59eb0963ee 100644
--- a/synapse/types/handlers/__init__.py
+++ b/synapse/types/handlers/__init__.py
@@ -31,7 +31,14 @@ else:
     from pydantic import Extra
 
 from synapse.events import EventBase
-from synapse.types import DeviceListUpdates, JsonDict, JsonMapping, StreamToken, UserID
+from synapse.types import (
+    DeviceListUpdates,
+    JsonDict,
+    JsonMapping,
+    SlidingSyncStreamToken,
+    StreamToken,
+    UserID,
+)
 from synapse.types.rest.client import SlidingSyncBody
 
 if TYPE_CHECKING:
@@ -329,7 +336,7 @@ class SlidingSyncResult:
         def __bool__(self) -> bool:
             return bool(self.to_device or self.e2ee)
 
-    next_pos: StreamToken
+    next_pos: SlidingSyncStreamToken
     lists: Dict[str, SlidingWindowList]
     rooms: Dict[str, RoomResult]
     extensions: Extensions
@@ -342,7 +349,7 @@ class SlidingSyncResult:
         return bool(self.lists or self.rooms or self.extensions)
 
     @staticmethod
-    def empty(next_pos: StreamToken) -> "SlidingSyncResult":
+    def empty(next_pos: SlidingSyncStreamToken) -> "SlidingSyncResult":
         "Return a new empty result"
         return SlidingSyncResult(
             next_pos=next_pos,