Be sure to migrate the instance before you remove the service.
The tricky part is to remove (decommission) a nova-compute service from the openstack hypervisor list. Not sure about Havana, but in Icehouse there's a freshly added API extension for that. It might also work in Havana, though. Sure, you could also just remove entries from the database, but that's gnarly.
As far as I know there's no novaclient python module support for that API call yet, so you might have to call it via raw HTTP call, as show below:
(code is a courtesy of a colleague of mine, thanks N.!)
1st, get the token from keystone:
(Use a tenant for which you have admin privileges.)
curl -d '{"auth":{"passwordCredentials":{"username": "admin","password": "42"},"tenantName": "myTenant"}}' -H "Content-Type: application/json" http://openstack:5000/v2.0/tokens
2nd, identify the id of the compute service you want to remove
(do this one way, or the other. Here's what worked for us -- using novaclient python module)
import novaclient.v1_1.client as nvclient
nova = nvclient.Client(**creds)
services = nova.services.list()
for service in services:
if service.host == "node-to-remove": print service.id
3rd, get the tenant-id (you will need it later)
keystone tenant-list | grep myTenant
4th, use token, tenant-id, and the service-id to gracefully remove service from nova
curl -i -H "Content-Type: application/json" -X DELETE http://openstack:8774/v2/{tenant-id}/os-services/{service-id} -H "User-Agent: python-keystoneclient" -H "X-Auth-Token: {token}"
You're done.
If everything worked fine, you should no longer see your nova-compute service in the output of the
nova service-list
nor in the hypervisor list in the dashboard.
