nova like many other distibuted services has many actors that work together within the system.

when updating or upgrading nova it is unsafe to stop the service or restart them while there are ongerion opartions as that can leave the workslods in a broken state

to address this nova should provide a way to gracefully shutdown the services.

This could take many form

• a per binary endpoint to ask for graceful shutdown
• a top level API endpoint to query the state or runign operations and disabel the acceptance of new requests form the public endpoint.
• better docs on how to manually do this

the detail fo this will be left to the design task as there is a lot to discuss and condier to enable this in a future release.