Example Spec - The title of your blueprint¶

Use Cases¶

What use cases does this address? What impact on actors does this change have? Ensure you are clear about the actors in each use case: Developer, End User, Deployer etc.

Alternatives¶

What other ways could we do this thing? Why aren’t we using those? This doesn’t have to be a full literature review, but it should demonstrate that thought has been put into why the proposed solution is an appropriate one.

Data model impact¶

Changes which require modifications to the data model often have a wider impact on the system. The community often has strong opinions on how the data model should be evolved, from both a functional and performance perspective. It is therefore important to capture and gain agreement as early as possible on any proposed changes to the data model.

Questions which need to be addressed by this section include:

• What new data objects and/or database schema changes is this going to require?
• What database migrations will accompany this change.
• How will the initial set of new data objects be generated, for example if you need to take into account existing instances, or modify other existing data describe how that will work.

REST API impact¶

Each API method which is either added or changed should have the following

• Specification for the method
  • A description of what the method does suitable for use in user documentation
  • Method type (POST/PUT/GET/DELETE)
  • Normal http response code(s)
  • Expected error http response code(s)
    • A description for each possible error code should be included describing semantic errors which can cause it such as inconsistent parameters supplied to the method, or when an instance is not in an appropriate state for the request to succeed. Errors caused by syntactic problems covered by the JSON schema definition do not need to be included.
  • URL for the resource
    • URL should not include underscores, and use hyphens instead.
  • Parameters which can be passed via the url
  • JSON schema definition for the request body data if allowed
    • Field names should use snake_case style, not CamelCase or MixedCase style.
  • JSON schema definition for the response body data if any
    • Field names should use snake_case style, not CamelCase or MixedCase style.
• Example use case including typical API samples for both data supplied by the caller and the response
• Discuss any policy changes, and discuss what things a deployer needs to think about when defining their policy.

Note that the schema should be defined as restrictively as possible. Parameters which are required should be marked as such and only under exceptional circumstances should additional parameters which are not defined in the schema be permitted (eg additionaProperties should be False).

Reuse of existing predefined parameter types such as regexps for passwords and user defined names is highly encouraged.

Security impact¶

Describe any potential security impact on the system. Some of the items to consider include:

• Does this change touch sensitive data such as tokens, keys, or user data?
• Does this change alter the API in a way that may impact security, such as a new way to access sensitive information or a new way to login?
• Does this change involve cryptography or hashing?
• Does this change require the use of sudo or any elevated privileges?
• Does this change involve using or parsing user-provided data? This could be directly at the API level or indirectly such as changes to a cache layer.
• Can this change enable a resource exhaustion attack, such as allowing a single API interaction to consume significant server resources? Some examples of this include launching subprocesses for each connection, or entity expansion attacks in XML.

For more detailed guidance, please see the OpenStack Security Guidelines as a reference (https://wiki.openstack.org/wiki/Security/Guidelines). These guidelines are a work in progress and are designed to help you identify security best practices. For further information, feel free to reach out to the OpenStack Security Group at openstack-security@lists.openstack.org.

Notifications impact¶

Please specify any changes to notifications. Be that an extra notification, changes to an existing notification, or removing a notification.

Other end user impact¶

Aside from the API, are there other ways a user will interact with this feature?

• Does this change have an impact on python-cyborgclient? What does the user interface there look like?

Performance Impact¶

Describe any potential performance impact on the system, for example how often will new code be called, and is there a major change to the calling pattern of existing code.

Examples of things to consider here include:

• A periodic task might look like a small addition but if it calls conductor or another service the load is multiplied by the number of nodes in the system.
• Scheduler filters get called once per host for every instance being created, so any latency they introduce is linear with the size of the system.
• A small change in a utility function or a commonly used decorator can have a large impacts on performance.
• Calls which result in a database queries (whether direct or via conductor) can have a profound impact on performance when called in critical sections of the code.
• Will the change include any locking, and if so what considerations are there on holding the lock?

Other deployer impact¶

Discuss things that will affect how you deploy and configure OpenStack that have not already been mentioned, such as:

• What config options are being added? Should they be more generic than proposed (for example a flag that other hypervisor drivers might want to implement as well)? Are the default values ones which will work well in real deployments?
• Is this a change that takes immediate effect after its merged, or is it something that has to be explicitly enabled?
• If this change is a new binary, how would it be deployed?
• Please state anything that those doing continuous deployment, or those upgrading from the previous release, need to be aware of. Also describe any plans to deprecate configuration values or features. For example, if we change the directory name that instances are stored in, how do we handle instance directories created before the change landed? Do we move them? Do we have a special case in the code? Do we assume that the operator will recreate all the instances in their cloud?

Developer impact¶

Discuss things that will affect other developers working on OpenStack, such as:

• If the blueprint proposes a change to the driver API, discussion of how other hypervisors would implement the feature is required.

Assignee(s)¶

Who is leading the writing of the code? Or is this a blueprint where you’re throwing it out there to see who picks it up?

If more than one person is working on the implementation, please designate the primary author and contact.

Primary assignee:

<launchpad-id or None>

Other contributors:

<launchpad-id or None>

Work Items¶

Work items or tasks – break the feature up into the things that need to be done to implement it. Those parts might end up being done by different people, but we’re mostly trying to understand the timeline for implementation.