Increase timeout for client fed requests known to be long to answer

changelog.d/15001.misc

@@ -0,0 +1 @@
+Increase client timeout for potentially long federation requests. It should improve joining behavior of big rooms.

synapse/federation/transport/client.py

@@ -79,6 +79,8 @@ async def get_room_state_ids(
             destination,
             path=path,
             args={"event_id": event_id},
+            # This can take a looooooong time for large rooms.
+            timeout=600_000,
             try_trailing_slash_on_400=True,
         )
 
@@ -345,6 +347,8 @@ async def send_join_v1(
             destination=destination,
             path=path,
             data=content,
+            # This can take a looooooong time for large rooms.
+            timeout=600_000,
             parser=SendJoinParser(room_version, v1_api=True),
         )
 
@@ -371,6 +375,8 @@ async def send_join_v2(
             path=path,
             args=query_params,
             data=content,
+            # This can take a looooooong time for large rooms.
+            timeout=600_000,
             parser=SendJoinParser(room_version, v1_api=False),
         )