When trying to install 4.3 (and probably earlier versions), if the hostname is too long rabbitmq will fail to start due to erlang failing.
With this hostname: server-openstack-manager-vm.yaml-nodejs-host-ytloi8.openstackloc
No longs were seen for rabbit (at all), but errors were seen under journalctl -u cloudify-rabbitmq:
Feb 23 17:49:34 server-openstack-manager-vm.yaml-nodejs-host-ytloi8.openstackloc rabbitmqctl[9615]: Kernel pid terminated (application_controller) ({application_start_failure,kernel,{{shutdown,{failed_to_start_child,inet_db,{'EXIT',{function_clause,[{inet_config,set_hostname,[{error,enametoolong}]
This almost certainly affects every release since we started using rabbit (3.0.0), but I am marking it only for 4.3 at the moment as I have not confirmed on anything earlier..