POC for QuotaManagement

Introduction

This Page explains the Proof of Concept for Quota Management in the Openstack Hierarchical Multitenancy setup.

Setup

Please see the following picture for an example Hierarchical Multitenancy setup.

Authentication

Every user has to authenticate with keystone using a project scope. For example, userA can authenticate using the project scope as "ProjH.ProjA". The cloud admin can authenticate using any scope. When authenticated, the entire hierarchy is parsed starting from the scope project till the head node and construct the roles the user has at each level. See the following examples.

Example 1

Cloud Admin authenticates at "ProjH", keystone will send the following information (or token) for this session.
Scope
ProjH
Roles (find role at each project level upto the head node)

admin

Example 2

Cloud Admin authenticates at "ProjH.ProjA.ProjA1", keystone will send the following information (or token) for this session.
Scope
ProjH.ProjA.ProjA1
Roles (find role at each project level upto the head node)

admin

Example 3

User A authenticates at "ProjH.ProjA", keystone will send the following information (or token) for this session.
Scope
ProjH.ProjA
Roles (find role at each project level upto the head node)

project-admin, member

Example 4

User A authenticates at "ProjH.ProjA.ProjA1.ProjA3", keystone will send the following information (or token) for this session.
Scope
ProjH.ProjA.ProjA1.ProjA3
Roles (find role at each project level upto the head node)

project-admin, member

̽Noteː

It is important to limit the maximum depth of the Project Hierarchy. Otherwise, the paring may take a very long time.

Example 5

User B tries to authenticates at "ProjH.ProjA" but keystone will reject the authentication as User B does not have any role at "ProjH.ProjA". That means User B is not part of Project "ProjH.ProjA". User B can authenticate using the scope as "ProjH.ProjA.ProjA1.ProjA3" or "ProjH.ProjB.ProjB2".

Quota Tables

There are four tables useful for Quota Management, namely "quotas", "quota_usages", "project_user_quotas" and "reservations" respectively.

Table	Description	Important Fields
quotas	Stores the quota values for resources (like instances, cores etc) of a Project	project_id
project_user_quotas	Stores the quota allotment to a User in a Project	project_id, user_id
quota_usages	Stores the quota already in use by a User in a Project	project_id, user_id
reservations	Stores the reservations made for a resource by a User in a Project	project_id, user_id

The project_id field in these tables stores the project complete hierarchy, like if quota values are defined for "ProjA1", then the project_id is "ProjH.ProjA.ProjA1".

API URLs

The URLs does not need to include any project names up to the authentication scope. The URLs only need to include the hierarchy after the scope for executing an operation. For example, if User A authenticates using scope as "ProjH.ProjA" and the User A want to update the quotas assigned to "ProjH.ProjA.ProjA1.ProjA3", then the URL can be like

PUT Request -> http://<nova listening ip>:8774/v3/os-quota-sets?project_id=ProjA1.ProjA3

When the above URL fired, the complete hierarchy will be formed by prepend the scope id to the project_id in the URL, that means here it will be "ProjH.ProjA.ProjA1.ProjA3". Now, the program can check the role possessed by the user at this level (User A has memeber and project-admin roles at this level). As the user possess the "project-admin" role, the update operation on quotas is allowed.

The Keystone context will have a field which gives information about the roles at each level of the hierarchy starting from the scope level (as explained in the examples listed under Authentication Section). We can call this field as "rolesList". The "project_id" has the full hierarchy like "ProjH.ProjA.ProjA1.ProjA3"

"admin_or_project_admin":  "is_admin:True or  roleProjectAdmin:rolesList:%(project_id)"

This means that the user satisfies one of the following condition

Cloud Admin
function "roleProjectAdmin" will check that user has a project-admin role in the project_id using the the context field "rolesList"

The policy rules for the quota extension can be

"owner": "roleMember:rolesList:%(project_id)"   (means that user has any role except project-admin in the project)
"admin_or_project_admin_or_owner": "rule:admin_or_project_admin or rule:owner"
 
"compute_extension:quotas:show": "rule:admin_or_project_admin_or_owner",
"compute_extension:quotas:update": "rule:admin_or_project_admin",
"compute_extension:quotas:delete": "rule:admin_or_project_admin"

POC Demo code

Please check the code snippets for this setup at
https://github.com/vinodkumarboppanna/POC-For-Quotas/commit/391e9108fa579d292880c8836cadfd7253586f37

Concerns

As nova keeps the complete project hierarchy in the Quotas table, it is necessary to notify nova about any changes in the hierarchy. For example, nova stores Quotas of Project "ProjH.ProjA.ProjA1" in the table and User removes the project "ProjA1" from the keystone, then nova should be notified about this.