Precompute joined hosts and store in Redis (#9198)

stubs/txredisapi.pyi

@@ -15,11 +15,21 @@
 
 """Contains *incomplete* type hints for txredisapi.
 """
-from typing import List, Optional, Type, Union
+from typing import Any, List, Optional, Type, Union
 
 class RedisProtocol:
     def publish(self, channel: str, message: bytes): ...
     async def ping(self) -> None: ...
+    async def set(
+        self,
+        key: str,
+        value: Any,
+        expire: Optional[int] = None,
+        pexpire: Optional[int] = None,
+        only_if_not_exists: bool = False,
+        only_if_exists: bool = False,
+    ) -> None: ...
+    async def get(self, key: str) -> Any: ...
 
 class SubscriberProtocol(RedisProtocol):
     def __init__(self, *args, **kwargs): ...