Open Stack

Hello Again!

At the meeting last week we discussed some options around getting true multitenancy in nova. The use case that we are trying to support can be described as follows:

"Martha, the owner of ProductionIT provides it services to multiple Enterprise clients. She would like to offer cloud services to Joe at WidgetMaster, and Sam at SuperDevShop. Joe is a Development Manager for WidgetMaster and he has multiple QA and Development teams with many users. Joe needs the ability create users, projects, and quotas, as well as the ability to list and delete resources across WidgetMaster. Martha needs to be able to set the quotas for both WidgetMaster and SuperDevShop; manage users, projects, and objects across the entire system; and set quotas for the client companies as a whole. She also needs to ensure that Joe can't see or mess with anything owned by Sam."

As per the plan I outlined in the meeting I have implemented a Proof-of-Concept that would allow me to see what changes were required in nova to get scoped tenancy working. I used a simple approach of faking out heirarchy by prepending the id of the larger scope to the id of the smaller scope. Keystone uses uuids internally, but for ease of explanation I will pretend like it is using the name. I think we can all agree that ‘orga.projecta’ is more readable than ‘b04f9ea01a9944ac903526885a2666dec45674c5c2c6463dad3c0cb9d7b8a6d8’.

The code basically creates the following five projects:

orga
orga.projecta
orga.projectb
orgb
orgb.projecta

I then modified nova to replace everywhere where it searches or limits policy by project_id to do a prefix match. This means that someone using project ‘orga’ should be able to list/delete instances in orga, orga.projecta, and orga.projectb.

You can find the code here:

  https://github.com/vishvananda/devstack/commit/10f727ce39ef4275b613201ae1ec7655bd79dd5f
  https://github.com/vishvananda/nova/commit/ae4de19560b0a3718efaffb6c205c7a3c372412f

Keeping in mind that this is a prototype, but I’m hoping to come to some kind of consensus as to whether this is a reasonable approach. I’ve compiled a list of pros and cons.

Pros:

  * Very easy to understand
  * Minimal changes to nova
  * Good performance in db (prefix matching uses indexes)
  * Could be extended to cover more complex scenarios like multiple owners or multiple scopes

Cons:

  * Nova has no map of the hierarchy
  * Moving projects would require updates to ownership inside of nova
  * Complex scenarios involving delegation of roles may be a bad fit
  * Database upgrade to hierarchy could be tricky

If this seems like a reasonable set of tradeoffs, there are a few things that need to be done inside of nova bring this to a complete solution:

  * Prefix matching needs to go into oslo.policy
  * Should the tenant_id returned by the api reflect the full ‘orga.projecta’, or just the child ‘projecta’ or match the scope: i.e. the first if you are authenticated to orga and the second if you are authenticated to the project?
  * Possible migrations for existing project_id fields
  * Use a different field for passing ownership scope instead of overloading project_id
  * Figure out how nested quotas should work
  * Look for other bugs relating to scoping

Also, we need to decide how keystone should construct and pass this information to the services. The obvious case that could be supported today would be to allow a single level of hierarchy using domains. For example, if domains are active, keystone could pass domain.project_id for ownership_scope. This could be controversial because potentially domains are just for grouping users and shouldn’t be applied to projects.

I think the real value of this approach would be to allow nested projects with role inheritance. When keystone is creating the token, it could walk the tree of parent projects, construct the set of roles, and construct the ownership_scope as it walks to the root of the tree.

Finally, similar fixes will need to be made in the other projects to bring this to a complete solution.

Please feel free to respond with any input, and we will be having another Hierarchical Multitenancy Meeting on Friday at 1600 UTC to discuss.

Vish

On Jan 28, 2014, at 10:35 AM, Vishvananda Ishaya <vishvananda at gmail.com> wrote:

> Hi Everyone,
> 
> I apologize for the obtuse title, but there isn't a better succinct term to describe what is needed. OpenStack has no support for multiple owners of objects. This means that a variety of private cloud use cases are simply not supported. Specifically, objects in the system can only be managed on the tenant level or globally.
> 
> The key use case here is to delegate administration rights for a group of tenants to a specific user/role. There is something in Keystone called a “domain” which supports part of this functionality, but without support from all of the projects, this concept is pretty useless.
> 
> In IRC today I had a brief discussion about how we could address this. I have put some details and a straw man up here:
> 
> https://wiki.openstack.org/wiki/HierarchicalMultitenancy
> 
> I would like to discuss this strawman and organize a group of people to get actual work done by having an irc meeting this Friday at 1600UTC. I know this time is probably a bit tough for Europe, so if we decide we need a regular meeting to discuss progress then we can vote on a better time for this meeting.
> 
> https://wiki.openstack.org/wiki/Meetings#Hierarchical_Multitenancy_Meeting
> 
> Please note that this is going to be an active team that produces code. We will *NOT* spend a lot of time debating approaches, and instead focus on making something that works and learning as we go. The output of this team will be a MultiTenant devstack install that actually works, so that we can ensure the features we are adding to each project work together.
> 
> Vish

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