Hi @pablo , thank you for your help today. I was using Ansible to upgrade my sandbox 3 node cluster. It turned out for some reason Ansible failed to restart Opensearch during the upgrade, caused the whoami call failure. I had to manually restart Opensearch on the nodes using systemctl to update the running version to 2.4, then restarted Ansible tasks to finish the upgrade successfully.
Also turned out I could do a version check before the whoami call. And if the running version does not match with expected version, restart it.
Any other work around for this issue is welcome.