Reviewing Patrole Code

Reviewing Patrole Code

To start read the OpenStack Common Review Checklist

Ensuring code is executed

Any new test or change to an existing test has to be verified in the gate. This means that the first thing to check with any change is that a gate job actually runs it. Tests which aren’t executed either because of configuration or skips should not be accepted.

Execution time

Along with checking that the jobs log that a new test is actually executed, also pay attention to the execution time of that test. Patrole already runs hundreds of tests per job in its check and gate pipelines and it is important that the overall runtime of the jobs be constrained as much as possible. Consider applying the @decorators.attr(type='slow') test attribute decorator to a test if its runtime is longer than 30 seconds.

Unit Tests

For any change that adds new functionality to common functionality unit tests are required. This is to ensure we don’t introduce future regressions and to test conditions which we may not hit in the gate runs.

API Stability

Tests should only be added for published stable APIs. If a patch contains tests for an API which hasn’t been marked as stable or for an API which doesn’t conform to the API stability guidelines then it should not be approved.

Similarly, tests should only be added for policies that are covered by policy in code documentation. Any existing tests that test policies not covered by such documentation are either:

  • part of a service that has not yet migrated to policy in code; or

  • legacy in the sense that they were created prior to policy in code

For the first bullet, the tests should not be considered stable, but should be kept around to maintain coverage. These tests are a best-effort attempt at offering RBAC test coverage for the service that has not yet migrated to policy in code.

For the second bullet, the tests should be updated to conform to policy in code documentation, if applicable.

Reject Copy and Paste Test Code

When creating new tests that are similar to existing tests it is tempting to simply copy the code and make a few modifications. This increases code size and the maintenance burden. Such changes should not be approved if it is easy to abstract the duplicated code into a function or method.

Tests overlap

When a new test is being proposed, question whether this feature is not already tested with Patrole. Patrole has more than 600 tests, spread amongst many directories, so it’s easy to introduce test duplication.

Test Duplication

Test duplication means:

  • testing an API endpoint in more than one test

  • testing the same policy in more than one test

For the first bullet, try to avoid calling the same API inside the self.override_role() call.


If the same API is tested against different policies, consider combining the different tests into only 1 test, that tests the API against all the policies it enforces.

For the second bullet, try to avoid testing the same policies across multiple tests.


This is not always possible since policy granularity doesn’t exist for all APIs. In cases where policy granularity doesn’t exist, make sure that the policy overlap only exists for the non-granular APIs that enforce the same policy.

Being explicit

When tests are being added that depend on a configurable feature or extension, polling the API to discover that it is enabled should not be done. This will just result in bugs being masked because the test can be skipped automatically. Instead the config file should be used to determine whether a test should be skipped or not. Do not approve changes that depend on an API call to determine whether to skip or not.

Multi-Policy Guidelines

Care should be taken when using multiple policies in an RBAC test. The following guidelines should be followed before deciding to add multiple policies to a Patrole test.

General Multi-policy API Code Guidelines

The list below enumerates guidelines beginning with those with the highest priority and ending with those with the lowest priority. A higher priority item takes precedence over lower priority items.

  1. Order the policies in the rules parameter chronologically with respect to the order they’re called by the API endpoint under test.

  2. Only use policies that map to the API by referencing the appropriate policy in code documentation.

  3. Only include the minimum number of policies needed to test the API correctly: don’t add extraneous policies.

  4. If possible, only use policies that directly relate to the API. If the policies are used across multiple APIs, try to omit it. If a “generic” policy needs to be added to get the test to pass, then this is fair game.

  5. Limit the number of policies to a reasonable number, such as 3.

Neutron Multi-policy API Code Guidelines

Because Neutron can raise a 403 or 404 following failed authorization, Patrole uses the expected_error_codes parameter to accommodate this behavior. Each policy action enumerated in rules must have a corresponding entry in expected_error_codes. Each expected error code must be either a 403 or a 404, which indicates that, when policy enforcement fails for the corresponding policy action, that error code is expected by Patrole. For more information about these parameters, see RBAC Rule Validation Module.

The list below enumerates additional multi-policy guidelines that apply in particular to Neutron. A higher priority item takes precedence over lower priority items.

  1. Order the expected error codes in the expected_error_codes parameter chronologically with respect to the order each corresponding policy in rules is authorized by the API under test.

  2. Ensure the Neutron Multi-policy Validation is followed when determining the expected error code for each corresponding policy.

The same guidelines under General Multi-policy API Code Guidelines should be applied afterward.

Release Notes

Release notes are how we indicate to users and other consumers of Patrole what has changed in a given release. There are certain types of changes that require release notes and we should not approve them without including a release note. These include but aren’t limited to, any addition, deprecation or removal from the framework code, any change to configuration options (including deprecation), major feature additions, and anything backwards incompatible or would require a user to take note or do something extra.

Deprecated Code

Sometimes we have some bugs in deprecated code. Basically, we leave it. Because we don’t need to maintain it. However, if the bug is critical, we might need to fix it. When it will happen, we will deal with it on a case-by-case basis.

When to approve

  • Every patch can be approved with single +2 which means single reviewer can approve.

  • It’s OK to hold off on an approval until a subject matter expert reviews it.

  • If a patch has already been approved but requires a trivial rebase to merge, you do not have to wait for a +2, since the patch has already had +2’s. With single +2 rule, this means that author can also approve this case if he/she has approve rights.