I have solved this problem by adding interface section. I was also having the similar config as described above (with hostnames) and started not joining the cluster after I upgrade to 3.9.1. I think earlier versions if we just provide hostnames in <tcp-ip> section it used to join but now need to provide interfaces to get connected. The below config works with 3.9.1
| <join> | |
| <multicast enabled="false" /> | |
| <tcp-ip enabled="true"> | |
| <member>ip_of_node_1</member> | |
| <member>ip_of_node_2</member> | |
| </tcp-ip> | |
| </join> | |
| <interfaces enabled="true"> | |
| <interface>IP_ranges_covers both the node</interface> | |
| </interfaces> |