Governance/APIGuidelines

API Guidelines for Projects (DRAFT)

The intent of this page is to provide guidelines for OpenStack projects for the look and feel of their REST API interfaces in order that we have a consistent look and feel across all the projects. Changing the APIs of older projects is a long term process as need to retain backwards compatibility for users, but over time we can all slowly converge to a more consistent API.

Note: This documentation is currently very much in development - an alpha version for discussion amongst those from the various projects who are interested in cross project API consistency. Feel free to add comments and guidelines you think we need to standardise on.

API Terminology

Common Issues

tenant vs project
- We should always use project.
instances vs servers
- We should always use servers.

Extensions

Use of API extensions is generally discouraged, though historically many projects have them. Where we have extensions we should from the API client point of view have them look the same. If a project supports extensions they should support the following features:

Versioning
- All extensions should have client visible versioning to be able to signal changes to the API (both backwards compatible and backwards incompatible changes. Versioning may be of the form of versions on individual extensions or an api-wide microversion which allows clients to select a specific version of an API.
Discoverability mechanism
- Ceilometer capabilities http://docs.openstack.org/developer/ceilometer/webapi/v2.html#capabilities
- Marconi use of home doc and JSON Schema https://wiki.openstack.org/wiki/Marconi/specs/api/v1.1#Get_Home_Document
Extensions should be kept to a minimum. The core API should be reviewed regularly to incorporate features which were formerly extensions
- Too many extensions results in portability issues