As part of planned host maintenance, tried to play around how it could be

#In Nova hostid is uniq identifier for host for a tenant/project (somebody else than admin):
import hashlib
projectid = str(instance.project_id)
host = instance.host
hostid = hashlib.sha224(projectid + host).hexdigest()

#As other than admin is not allowed to know hostname, they should refer to it with other uniq identifier.
#Nova has hostid for this. Here with some imaginery projectid and host:
projectid = "8a3169016ed14558bf062b1a4ce21737"
host = "compute.host.example.com"
hostid = hashlib.sha224(projectid + host).hexdigest()
print hostid
fc9ec958261e33fb40e4ff08e3602797143817c15ee47a5bd3c048eb

#In Craton admin can refer host by its name, where again other users should use hostid as they should not be aware about the hostname.

#admin sets host_details to host as namespace:
craton host-set-vars compute.host.example.com /host_details

#admin sets maintenance_state variable to host_details namespace:
craton host-set-vars compute.host.example.com /host_details/maintenance_state="PLANNED_MAINTENANCE"

#Can one set multiple variables with one call? This would be important to not to trigger notification on each change?
#There could be something more like:
maintenance_reason="firmware update"
maintenance_start="2016-03-22T00:46:25Z",
maintenance_end="2016-03-22T04:46:25Z",

#Notification would be triggered with payload from host_details namespace with host from host namespace included
#Assuming this can be admin level as other user would not directly consume notification, but alarm

#Based on Nova discussions and Nova spec: https://review.openstack.org/310510
#in Nova you would set to nova-compute service a link to Craton:

    PUT /v2.1/{tenant_id}/os-services/host-details
    {
      "host": "compute.host.example.com",
      "binary": "nova-compute",
      "host_details": "http://${CRATON_IP}:8080/v1/hosts/host_details/compute.host.example.com",
    }
    200 OK
    {
      "service": {
      "host": "my.host.example.com",
      "binary": "nova-compute",
      "host_details": "http://${CRATON_IP}:8080/v1/hosts/host_details/compute.host.example.com",
      }
    }

    #In Nova server API project could get link to Craton host data he is allowed to see.
    #Nova translates internally the url given to nova-compute service host_details
    #by replacing "hostname" with project specific hostid
    GET /v2.1/8a3169016ed14558bf062b1a4ce21737/servers/{server_id}
    200 OK
    {
      "server": {
        ...
        "host_details": "http://${CRATON_IP}:8080/v1/hosts/host_details/fc9ec958261e33fb40e4ff08e3602797143817c15ee47a5bd3c048eb",
        ...
      }
    }

How would this work for project: "GET http://${CRATON_IP}:8080/v1/hosts/host_details/fc9ec958261e33fb40e4ff08e3602797143817c15ee47a5bd3c048eb"
Data should be same as
"GET http://${CRATON_IP}:8080/v1/hosts/host_details"
Unless admin would place some variable not to be seen by other users.