Cinder internal tenant

Cinder internal tenant

https://blueprints.launchpad.net/cinder/+spec/cinder-internal-tenant

This spec proposes the addition of config options and internal plumbing required for a cinder-internal tenant. This tenant can then be used by Cinder as the owner of internal objects that we don’t really want owned by any normal users.

Problem description

There are several use cases for ‘internal’ cinder objects where we would like to prevent a normal user from seeing them. The approach that seems to have the most backing is to a special tenant that cinder can use for owning these internal volumes/snapshots/etc.

Use Cases

There are a few different use cases for the internal tenant. The generic use case is for any volume or snapshot object in Cinder that we do not want exposed to normal users, but would like to keep track of and have treated as normal volumes and snapshots.

There are a few features which would be able to take advantage of this:

  • Image Caching - Volumes (and potentially snapshots) that are used as part of the image cache could be owned by the tenant.
  • Volume Migration - Temporary volumes while migrations are taking place could be owned by the cinder-internal tenant.
  • Non-Disruptive Backups - Temporary snapshots and volumes could be owned by the cinder-internal tenant.

Proposed change

I think initially the easiest way to make this work is to add new config options that take in the credentials for the tenant. This would require an admin to create and configure the tenant manually and then set the values in cinder.conf. These config options will be:

  • cinder_internal_tenant_username
  • cinder_internal_tenant_password

These config options will default to ‘None’. For some features like the image cache this isn’t such a big deal. If the credentials are none, and the tenant is unavailable the cache just won’t actually create cache objects and things fall back to the original functionality. It will however be more difficult for features like migration or backups where they may not be able to fall back nicely to a behavior that does not need the credentials.

Things like quota and other permissions would be managed by an admin only, cinder will not modify things automatically. In the future it would be possible to have default values for the config options, and allow cinder to mange the tenant. That functionality will be out of scope for this initial implementation.

For the initial change I don’t think we should keep any of this info in the cinder db. Everything comes from the config file and is re-checked at startup.

Any usage of the tenants objects should assume they could be deleted or cleaned up at any time, I don’t think this is any different than the case today where a user could delete a second volume halfway through migration though. So this is not a regression. The idea behind this being that as an admin you could periodically clean these objects up if they start to accumulate, but you wouldn’t really need to worry about which ones are ‘safe’.

Alternatives

Another way to approach this problem is to add ‘hidden’ flags to volumes and snapshots. The biggest downside of this is that all API’s need to then know about this and start filtering, and potentially clients and commands need new ‘–hidden’ or ‘–show-all’ kind of flags. In addition these hidden volumes may either take quota from a real user or not be accounted for at all.

Data model impact

None

REST API impact

None

Security impact

Care will need to be taken to ensure the tenant credentials are not exposed to anyone other than cloud administrators and that users cannot create volumes or other objects as the internal tenant.

Notifications impact

None

Other end user impact

This change by itself shouldn’t have any end user impact. Things built on top of it may change what a user sees while using commands like migrate.

Performance Impact

None

Other deployer impact

New config options and setup steps when configuring cinder.

Additional documentation to read.

Developer impact

New internal API’s to use to create objects as the internal tenant.

Implementation

Assignee(s)

Primary assignee:
patrick-east
Other contributors:
None

Work Items

  • Add in support for the new config options.
  • Add in utility functions to get the tenant information and anything else required to use the internal tenant for operations.
  • Possibly add support in to DevStack to configure this by default for future development on top of the feature.
  • Documentation on how to create and configure the tenant.

Dependencies

None

Testing

Unit tests for the utility functions.

This change by itself won’t require tempest test changes or additions, but features utilizing it will.

Documentation Impact

Creative Commons Attribution 3.0 License

Except where otherwise noted, this document is licensed under Creative Commons Attribution 3.0 License. See all OpenStack Legal Documents.

cinder-specs 0.0.1.dev432