Modify ‘is_default’ behavior relative to ‘is_protected’ for templates

Modify ‘is_default’ behavior relative to ‘is_protected’ for templates

https://blueprints.launchpad.net/sahara/+spec/replace-is-default

With the addition of the general is_protected field on all objects, the is_default field on cluster and node group templates is semi-redundant. Its semantics should be changed; specifically, gating of update and delete operations should be handled exclusively by is_protected. The is_default field should still be used to identify default templates for bulk update and delete operations by the sahara-templates tool.

Problem description

The is_protected and is_default fields both control gating of update and delete operations. This overlap is not clean and should be resolved to avoid confusion for end users and developers alike and to decrease complexity in code maintenance.

Gating of update or delete operations should no longer be associated with the is_default field. Instead, it should only mark the default templates created with the sahara-templates tool so that bulk update and delete operations continue to function as is.

Proposed change

Remove the checks in the sahara db layer that raise exceptions based on the is_default field for template update and delete operations. This will leave the gating under the control of is_protected. Note that there will no longer be an error message that informs the user of failure to update or delete a default template – it will be phrased in terms of the is_protected field instead.

Modify all of the default template sets bundled with sahara to include the is_protected field set to True. This will ensure that templates used as-is from the sahara distribution will be created with update and delete operations hindered.

Provide a database migration that sets is_protected to True for all templates with is_default set to True. This will guarantee the hindrance on update and delete operations continues for existing default templates.

Currently, sahara will allow update and delete of default templates if the ignore_defaults flag is set on the conductor methods. Change the name and handling of this flag slightly so that if it is set, sahara will ignore the is_protected flag instead. This will allow the sahara-templates tool to easily update and delete default templates without having to first clear the is_protected flag.

Write a documentation section on default templates best practices. Given the addition of is_protected and is_public and the changed semantics for is_default, provide some suggestions for best practices as follows: operators will be encouraged to load the default template sets in the admin or service tenant and then make them available to users with is_public. If modifications will be made to the default templates, they can be loaded, copied and modified and the resultant templates made available to users with is_public. This will ensure that the original default templates as bundled with sahara will always be available as a reference with is_protected set to True. Alternatively, an admin could copy the default templates directory from the sahara distribution to another location and modify them on disk before loading them.

Implications of the change: it will now be possible for tenants with default templates to set is_protected to True and then edit those templates. If a subsequent update of those templates is done from the sahara-templates tool, those edits will be overwritten. This should be made clear in the best practices documentation described above. Additionally, is_default will remain a field that is only settable from the sahara-templates tool so that the default sets can be managed as a group.

Alternatives

None. Goals of the original default templates implementation were:

1 allow offline update and delete of default templates 2 treat a group of node group and cluster templates as a coherent set 3 allow operation filtered by plugin and version

The first requirement precludes use of the sahara client to manage default templates. If we did not have the first requirement, we could conceivably use the sahara client to manage them but requirements two and three mean that we would need logic around the operations anyway. Lastly, removing the is_default field completely leaves us with a need for some other mechanism to identify default templates. It seems best to remove the overlapping functionality of is_default and is_protected but leave the rest of the current implementation unchanged.

Also, this could be deferred as part of the API V2 initiative, but since it has so little impact on the API (see below) it seems unnecessary to wait

Data model impact

None, but provide an appropriate migration to set is_protected to True for all existing templates with is_default set to True.

REST API impact

None, is_default is only accessible directly through the conductor layer.

Other end user impact

None

Deployer impact

Deployers should be familiar with the best practices documentation we will add concerning default templates.

Developer impact

None

Sahara-image-elements impact

None

Sahara-dashboard / Horizon impact

None

Implementation

Assignee(s)

Primary assignee:
tmckay
Other contributors:
None

Work Items

Remove code in the sahara db layer that rejects update or delete for defaults Update default templates bundled with sahara to include is_protected Add alembic migration for setting is_protected on existing defaults Review documentation and add a best practices section

Dependencies

None

Testing

Unit tests will be sufficient. Existing tests will be modified to prove that default templates may be updated and edited after this change, assuming is_protected is False. The existing tests on is_protected cover normal update/delete control.

Documentation Impact

Documentation on the sahara-templates tool may change slightly where it describes how to update or delete a default template, and we will add a best practices section as noted

References

None

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.

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