[openstack-dev] [keystone] Changing the project name uniqueness constraint

Henry Nash henrynash9 at mac.com
Thu Jun 2 23:22:56 UTC 2016


As you know, I have been working on specs that change the way we handle the uniqueness of project names in Newton. The goal of this is to better support project hierarchies, which as they stand today are restrictive in that all project names within a domain must be unique, irrespective of where in the hierarchy that projects sits (unlike, say, the unix directory structure where a node name only has to be unique within its parent). Such a restriction is particularly problematic when enterprise start modelling things like test, QA and production as branches of a project hierarchy, e.g.:


Obviously the idea of a project name (née tenant) being unique has been around since near the beginning of (OpenStack) time, so we must be cautions. There are two alternative specs proposed:

1) Relax project name constraints: https://review.openstack.org/#/c/310048/ <https://review.openstack.org/#/c/310048/> 
2) Hierarchical project naming: https://review.openstack.org/#/c/318605/ <https://review.openstack.org/#/c/318605/>

First, here’s what they have in common:

a) They both solve the above problem
b) They both allow an authorization scope to use a path rather than just a simple name, hence allowing you to address a project anywhere in the hierarchy
c) Neither have any impact if you are NOT using a hierarchy - i.e. if you just have a flat layer of projects in a domain, then they have no API or semantic impact (since both ensure that a project’s name must still be unique within a parent)

Here’s how the differ:

- Relax project name constraints (1), keeps the meaning of the ‘name’ attribute of a project to be its node-name in the hierarchy, but formally relaxes the uniqueness constraint to say that it only has to be unique within its parent. In other words, let’s really model this a bit like a unix directory tree.
- Hierarchical project naming (2), formally changes the meaning of the ‘name’ attribute to include the path to the node as well as the node name, and hence ensures that the (new) value of the name attribute remains unique.

While whichever approach we chose would only be included in a new microversion (3.7) of the Identity API, although some relevant APIs can remain unaffected for a client talking 3.6 to a Newton server, not all can be. As pointed out be jamielennox, this is a data modelling problem - if a Newton server has created multiple projects called “dev” in the hierarchy, a 3.6 client trying to scope a token simply to “dev” cannot be answered correctly (and it is proposed we would have to return an HTTP 409 Conflict error if multiple nodes with the same name were detected). This is true for both approaches.

Other comments on the approaches:

- Having a full path as the name seems duplicative with the current project entity - since we already return the parent_id (hence parent_id + name is, today, sufficient to place a project in the hierarchy).
- In the past, we have been concerned about the issue of what we do if there is a project further up the tree that we do not have any roles on. In such cases, APIs like list project parents will not display anything other than the project ID for such projects. In the case of making the name the full path, we would be effectively exposing the name of all projects above us, irrespective of whether we had roles on them. Maybe this is OK, maybe it isn’t.
- While making the name the path keeps it unique, this is fine if clients blindly use this attribute to plug back into another API to call. However if, for example, you are Horizon and are displaying them in a UI then you need to start breaking down the path into its components, where you don’t today.
- One area where names as the hierarchical path DOES look right is calling the /auth/projects API - where what the caller wants is a list of projects they can scope to - so you WANT this to be the path you can put in an auth request.

Given that neither can fully protect a 3.6 client, my personal preference is to go with the cleaner logical approach which I believe is the Relax project name constraints (1), with the addition of changing GET /auth/projects to return the path (since this is a specialised API that happens before authentication) - but I am open to persuasion (as the song goes).

There are those that might say that perhaps we just can’t change this. I would argue that since this ONLY affects people who actually create hierarchies and that today such hierarchical use is in its infancy, then now IS the time to change this. If we leave it too long, then it will become really hard to change what will by then have become a tough restriction.


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