Send USER_IP commands on a different Redis channel, in order to reduce traffic to workers that do not process these commands. (#12809)

synapse/replication/tcp/commands.py

@@ -58,6 +58,15 @@ class Command(metaclass=abc.ABCMeta):
         # by default, we just use the command name.
         return self.NAME
 
+    def redis_channel_name(self, prefix: str) -> str:
+        """
+        Returns the Redis channel name upon which to publish this command.
+
+        Args:
+            prefix: The prefix for the channel.
+        """
+        return prefix
+
 
 SC = TypeVar("SC", bound="_SimpleCommand")
 
@@ -395,6 +404,9 @@ class UserIpCommand(Command):
             f"{self.user_agent!r}, {self.device_id!r}, {self.last_seen})"
         )
 
+    def redis_channel_name(self, prefix: str) -> str:
+        return f"{prefix}/USER_IP"
+
 
 class RemoteServerUpCommand(_SimpleCommand):
     """Sent when a worker has detected that a remote server is no longer