2 files changed, 28 insertions, 8 deletions
diff --git a/synapse/replication/tcp/commands.py b/synapse/replication/tcp/commands.py
index 58a871c6d9..e616b5e1c8 100644
--- a/synapse/replication/tcp/commands.py
+++ b/synapse/replication/tcp/commands.py
@@ -267,27 +267,38 @@ class UserSyncCommand(Command):
     NAME = "USER_SYNC"
 
     def __init__(
-        self, instance_id: str, user_id: str, is_syncing: bool, last_sync_ms: int
+        self,
+        instance_id: str,
+        user_id: str,
+        device_id: Optional[str],
+        is_syncing: bool,
+        last_sync_ms: int,
     ):
         self.instance_id = instance_id
         self.user_id = user_id
+        self.device_id = device_id
         self.is_syncing = is_syncing
         self.last_sync_ms = last_sync_ms
 
     @classmethod
     def from_line(cls: Type["UserSyncCommand"], line: str) -> "UserSyncCommand":
-        instance_id, user_id, state, last_sync_ms = line.split(" ", 3)
+        device_id: Optional[str]
+        instance_id, user_id, device_id, state, last_sync_ms = line.split(" ", 4)
+
+        if device_id == "None":
+            device_id = None
 
         if state not in ("start", "end"):
             raise Exception("Invalid USER_SYNC state %r" % (state,))
 
-        return cls(instance_id, user_id, state == "start", int(last_sync_ms))
+        return cls(instance_id, user_id, device_id, state == "start", int(last_sync_ms))
 
     def to_line(self) -> str:
         return " ".join(
             (
                 self.instance_id,
                 self.user_id,
+                str(self.device_id),
                 "start" if self.is_syncing else "end",
                 str(self.last_sync_ms),
             )
diff --git a/synapse/replication/tcp/handler.py b/synapse/replication/tcp/handler.py
index 92c5a55acc..d9045d7b73 100644
--- a/synapse/replication/tcp/handler.py
+++ b/synapse/replication/tcp/handler.py
@@ -428,7 +428,11 @@ class ReplicationCommandHandler:
 
         if self._is_presence_writer:
             return self._presence_handler.update_external_syncs_row(
-                cmd.instance_id, cmd.user_id, cmd.is_syncing, cmd.last_sync_ms
+                cmd.instance_id,
+                cmd.user_id,
+                cmd.device_id,
+                cmd.is_syncing,
+                cmd.last_sync_ms,
             )
         else:
             return None
@@ -699,9 +703,9 @@ class ReplicationCommandHandler:
         )
 
         now = self._clock.time_msec()
-        for user_id in currently_syncing:
+        for user_id, device_id in currently_syncing:
             connection.send_command(
-                UserSyncCommand(self._instance_id, user_id, True, now)
+                UserSyncCommand(self._instance_id, user_id, device_id, True, now)
             )
 
     def lost_connection(self, connection: IReplicationConnection) -> None:
@@ -753,11 +757,16 @@ class ReplicationCommandHandler:
         self.send_command(FederationAckCommand(self._instance_name, token))
 
     def send_user_sync(
-        self, instance_id: str, user_id: str, is_syncing: bool, last_sync_ms: int
+        self,
+        instance_id: str,
+        user_id: str,
+        device_id: Optional[str],
+        is_syncing: bool,
+        last_sync_ms: int,
     ) -> None:
         """Poke the master that a user has started/stopped syncing."""
         self.send_command(
-            UserSyncCommand(instance_id, user_id, is_syncing, last_sync_ms)
+            UserSyncCommand(instance_id, user_id, device_id, is_syncing, last_sync_ms)
         )
 
     def send_user_ip(