Add unit test for event persister sharding (#8433)

synapse/replication/tcp/redis.py

@@ -15,7 +15,7 @@
 
 import logging
 from inspect import isawaitable
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Optional
 
 import txredisapi
 
@@ -228,3 +228,41 @@ class RedisDirectTcpReplicationClientFactory(txredisapi.SubscriberFactory):
         p.password = self.password
 
         return p
+
+
+def lazyConnection(
+    reactor,
+    host: str = "localhost",
+    port: int = 6379,
+    dbid: Optional[int] = None,
+    reconnect: bool = True,
+    charset: str = "utf-8",
+    password: Optional[str] = None,
+    connectTimeout: Optional[int] = None,
+    replyTimeout: Optional[int] = None,
+    convertNumbers: bool = True,
+) -> txredisapi.RedisProtocol:
+    """Equivalent to `txredisapi.lazyConnection`, except allows specifying a
+    reactor.
+    """
+
+    isLazy = True
+    poolsize = 1
+
+    uuid = "%s:%d" % (host, port)
+    factory = txredisapi.RedisFactory(
+        uuid,
+        dbid,
+        poolsize,
+        isLazy,
+        txredisapi.ConnectionHandler,
+        charset,
+        password,
+        replyTimeout,
+        convertNumbers,
+    )
+    factory.continueTrying = reconnect
+    for x in range(poolsize):
+        reactor.connectTCP(host, port, factory, connectTimeout)
+
+    return factory.handler