Policy sample file generation

https://blueprints.launchpad.net/oslo?searchtext=policy-sample-generation

It is useful to deployers to have a sample configuration file outlining all available options, and it is a burden on projects to try to keep that sample file up to date. It would be preferable to generate that file from policies registered in the project in the same way that it’s done for configuration options.

Problem description

Projects which provide a sample policy file need to manually keep that up to date with what’s being checked in the code. In practice it can often be out of date. If all used policies are already registered in code that sample file should just be generated.

Proposed change

The proposal is to add a few helpers to oslo.policy. These are intended to help deployers maintain and trim their policy files.

  1. An oslo-policy-sample-generator along the same lines as the oslo-config-generator that exists in oslo.config. A console script ‘oslo-policy-sample-generator’ will be added to oslo.policy. This script will look at the namespace(s) in an oslo.policy.policies entry point and from there load in a list of oslo_policy.policy.RuleDefault objects. The sample file will be generated from this list. RuleDefault objects may include a description string which will be included as a comment. Output will be in the yaml format since it can include comments.
  2. A method for generating a policy file that contains the effective configured policy. This will merge rules defined in a policy file with registered default rules and output a full policy file with the result. By referencing this file a deployer can know exactly how a rule is set.
  3. A method for retrieving a list of policies loaded from a policy file which match the default registered rules. These are policies that are not necessary to be in a policy file so this output will help deployers trim their file overrides.
  4. A method for generating a yaml version of a policy file. This will read in the current policy file(s) and output a yaml version of those rules. This can be used to convert from a json format poliy file to yaml format. It must be noted that rules are not sorted so the output may not be directly diffable against the output of #1 or #2 above.

Files to change:

  • olso_policy/generator.py (new file)
  • setup.cfg (register an entry point)

Alternatives

Policy sample files could continue to be maintained manually.

Impact on Existing APIs

A new “oslo-policy-sample-generator” console script would be registered in setup.cfg. This doesn’t affect existing APIs, it is purely additive.

Security impact

None

Performance Impact

None. This is done outside of a service running and serving requests.

Configuration Impact

Sample policy.yaml files can be generated. This does not affect any current configuration, it is a tool to help those who would like to configure their policies.

Developer Impact

Projects wishing to take advantage of this will need to register all policy checks in order to be included in the sample file. Developers should add this registration for existing policy checks, and register new policy checks when they are added.

Testing Impact

There is no direct testing impact here. However this does enable other projects to have a test job which ensure that the sample file can be generated. Details on how this might be accomplished will be documented as part of this change.

Implementation

Assignee(s)

Primary assignee:
alaski
Other contributors:
None

Milestones

Target Milestone for completion:
newton-1

Work Items

  • Add an oslo_policy/generator.py modeled after the one on oslo.config.
  • Add policy sample generation.
  • Add generation of effective policy.
  • Add method for determining default rule definitions in a policy file.
  • Add generation of yaml policy file from current policy file(s).
  • Add an entry_point to oslo.policy setup.cfg to create a console script.
  • Document how a consuming project might configure themselves to use the file generation ability, or setup a tox target to be used for testing.

Incubation

N/A

Adoption

Nova would like to use this

Library

N/A

Anticipated API Stabilization

N/A

Documentation Impact

The ability to generate policy files will be documented in developer facing documentation. Any deployer facing changes will be the responsibility of consuming projects to document as they switch over to using policy registration.

Dependencies

‘policy-in-code’ spec.

References

None

Note

This work is licensed under a Creative Commons Attribution 3.0 Unported License. http://creativecommons.org/licenses/by/3.0/legalcode