Return 400 When Bad Status Values are Received

Return 400 When Bad Status Values are Received

https://blueprints.launchpad.net/nova/+spec/response-for-invalid-status

A bug was found where passing an invalid status to the server listing API would return an empty list for a regular user, but would raise an exception and return a 500 error for admin users. That has since been fixed (https://review.openstack.org/#/c/335648/), but in the discussions about that bug it was felt that while fixing the exception was certainly correct, the list of valid status values is small and well-defined, so returning an empty list was not the desired behavior; instead, the user should get a 400 Bad Request instead.

Problem description

A bug was found when listing servers with a status filter that happened if an invalid status value was passed: https://bugs.launchpad.net/nova/+bug/1579706. It would only happen for admin users, because it would try to fetch extended server attributes, and that code expected instances to be present in the cache, and would throw a KeyError exception. While discussing that bug, though, it was felt that the non-admin response (returning an empty list) was not correct, either, since statuses are limited and well-documented, and an invalid status was much more likely to be a typo (such as ‘EROR’ instead of ‘ERROR’). The correct response in this case should be a 400 Bad Request, so that the user would be aware that they made a mistake, giving them the opportunity to correct it.

Use Cases

As a user, if I mistakenly ask the API to list servers with a status that does not exist, I want to know that I did something wrong with my request, as it is most likely a typo, and not an actual request for servers whose status is, say, ‘ACTVIE’, when I meant ‘ACTIVE’.

Proposed change

When a request to filter the list of servers by status is received, verify that the status is one of the defined statuses for a server. If it is not, return a 400 Bad Request.

Alternatives

We could just continue to treat all statuses as valid, and return an empty list when an invalid status is passed, and let the user deal with the results.

Data model impact

None

REST API impact

This is a change to the API, and will require a new microversion.

Security impact

None

Notifications impact

None

Other end user impact

None

Performance Impact

None

Other deployer impact

None

Developer impact

None

Implementation

Assignee(s)

Primary assignee:

<ed-leafe>

Other contributors:

<Dinesh Bhor>

Work Items

  • Check any status passed to the list servers API is valid, and if not, return a 400 Bad Request.

Dependencies

None

Testing

A new test will be added that verifies that an incorrect status in a server list request will raise a 400 Bad Request.

Documentation Impact

None. Users should not be expecting that incorrect statuses will work.

History

Creative Commons Attribution 3.0 License

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nova-specs