Use stream.current_token() and remove stream_positions() (#7172)

We move the processing of typing and federation replication traffic into their handlers so that `Stream.current_token()` points to a valid token. This allows us to remove `get_streams_to_replicate()` and `stream_positions()`.

synapse/replication/tcp/client.py

@@ -16,7 +16,7 @@
 """
 
 import logging
-from typing import TYPE_CHECKING, Dict
+from typing import TYPE_CHECKING
 
 from twisted.internet.protocol import ReconnectingClientFactory
 
@@ -100,23 +100,6 @@ class ReplicationDataHandler:
         """
         self.store.process_replication_rows(stream_name, token, rows)
 
-    def get_streams_to_replicate(self) -> Dict[str, int]:
-        """Called when a new connection has been established and we need to
-        subscribe to streams.
-
-        Returns:
-            map from stream name to the most recent update we have for
-            that stream (ie, the point we want to start replicating from)
-        """
-        args = self.store.stream_positions()
-        user_account_data = args.pop("user_account_data", None)
-        room_account_data = args.pop("room_account_data", None)
-        if user_account_data:
-            args["account_data"] = user_account_data
-        elif room_account_data:
-            args["account_data"] = room_account_data
-        return args
-
     async def on_position(self, stream_name: str, token: int):
         self.store.process_replication_rows(stream_name, token, [])
 

synapse/replication/tcp/handler.py

@@ -314,15 +314,7 @@ class ReplicationCommandHandler:
             self._pending_batches.pop(cmd.stream_name, [])
 
             # Find where we previously streamed up to.
-            current_token = self._replication_data_handler.get_streams_to_replicate().get(
-                cmd.stream_name
-            )
-            if current_token is None:
-                logger.warning(
-                    "Got POSITION for stream we're not subscribed to: %s",
-                    cmd.stream_name,
-                )
-                return
+            current_token = stream.current_token()
 
             # If the position token matches our current token then we're up to
             # date and there's nothing to do. Otherwise, fetch all updates