When I start node1 and create 2 sessions, I see (localhost:8000/mod_cluster-manager):

SessionIDs:
id: DrP58P0i889C9crgfGfHQQ__.node1 route: node1
id: PC4ET-Eeb0KJqsnuvcg0tA__.node1 route: node1

Then I start node2 and kill node1. Sessions now fail over to node2, but http://localhost:8000/mod_cluster-manager still shows

SessionIDs:
id: DrP58P0i889C9crgfGfHQQ__.node1 route: node1
id: PC4ET-Eeb0KJqsnuvcg0tA__.node1 route: node1
id: DrP58P0i889C9crgfGfHQQ__.node2 route: node2
id: PC4ET-Eeb0KJqsnuvcg0tA__.node2 route: node2

I think the node1-related sessions should be removed because node1 is down !