[openstack-dev] [Nova] RFC Host Maintenance

Sean Dague sean at dague.net
Thu Apr 7 10:36:20 UTC 2016

On 04/07/2016 03:26 AM, Juvonen, Tomi (Nokia - FI/Espoo) wrote:
> Hi Nova, Ops, stackers,
> I am trying to figure out different use cases and requirements there
> would be for host maintenance and would like to get feedback and
> transfer all this to spec and discussion what could and should land for
> Nova or other places.
> As working in OPNFV Doctor project that has the Telco perspective about
> related requirements, I started to draft a spec based on something
> smaller that would be nice to have in Nova and less complicated to have
> it in single cycle. Anyhow the feedback from Nova API team was to look
> this as a whole and gather more. This is why asking this here and not
> just trough spec, to get input for requirements and use cases with wider
> audience. Here is the draft spec proposing first just maintenance window
> to be added:
> _https://review.openstack.org/296995/_
> Here is link to OPNFV Doctor requirements:
> _http://artifacts.opnfv.org/doctor/docs/requirements/02-use_cases.html#nvfi-maintenance_
> _http://artifacts.opnfv.org/doctor/docs/requirements/03-architecture.html#nfvi-maintenance_
> _http://artifacts.opnfv.org/doctor/docs/requirements/05-implementation.html#nfvi-maintenance_
> Here is what I could transfer as use cases, but would ask feedback to
> get more:
> As admin I want to set maintenance period for certain host.
> As admin I want to know when host is ready to actions to be done by admin
> during the maintenance. Meaning physical resources are emptied.
> As owner of a server I want to prepare for maintenance to minimize downtime,
> keep capacity on needed level and switch HA service to server not
> affected by
> maintenance.
> As owner of a server I want to know when my servers will be down because of
> host maintenance as it might be servers are not moved to another host.
> As owner of a server I want to know if host is to be totally removed, so
> instead of keeping my servers on host during maintenance, I want to move
> them
> to somewhere else.
> As owner of a server I want to send acknowledgement to be ready for host
> maintenance and I want to state if servers are to be moved or kept on host.
> Removal and creating of server is in owner's control already. Optionally
> server
> Configuration data could hold information about automatic actions to be
> done
> when host is going down unexpectedly or in controlled manner. Also
> actions at
> the same if down permanently or only temporarily. Still this needs
> acknowledgement from server owner as he needs time for application level
> controlled HA service switchover.

While I definitely understand the value of these in a deployement, I'm a
bit concerned of baking all this structured data into Nova itself. As it
effectively means putting some degree of a ticket management system in
Nova that's specific to a workflow you've decided on here. Baked in
workflow is hard to change when the needs of an industry do.

My counter proposal on your spec was to provide a free form field
associated with maintenance mode which could contain a url linking to
the details. This could be a jira ticket, or a REST url for some other
service. This would actually be much like how we handle images in Nova,
with a url to glance to find more info.


Sean Dague

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