Adding a Method to the OpenStack Manila API

Adding a Method to the OpenStack Manila API

The interface to manila is a RESTful API. REST stands for Representational State Transfer and provides an architecture “style” for distributed systems using HTTP for transport. Figure out a way to express your request and response in terms of resources that are being created, modified, read, or destroyed. Manila’s API aims to conform to the guidelines set by OpenStack API SIG.

Routing

To map URLs to controllers+actions, manila uses the Routes package. See the routes package documentation for more information.

URLs are mapped to “action” methods on “controller” classes in manila/api/<VERSION>/router.py.

These are two methods of the routes package that are used to perform the mapping and the routing:

  • mapper.connect() lets you map a single URL to a single action on a controller.
  • mapper.resource() connects many standard URLs to actions on a controller.

Controllers and actions

Controllers live in manila/api/v1 and manila/api/v2.

See manila/api/v1/shares.py for an example.

Action methods take parameters that are sucked out of the URL by mapper.connect() or .resource(). The first two parameters are self and the WebOb request, from which you can get the req.environ, req.body, req.headers, etc.

Actions return a dictionary, and wsgi.Controller serializes that to JSON.

Faults

If you need to return a non-200, you should return faults.Fault(webob.exc .HTTPNotFound()) replacing the exception as appropriate.

Evolving the API

The v1 version of the manila API has been deprecated. The v2 version of the API supports micro versions. So all changes to the v2 API strive to maintain stability at any given API micro version, so consumers can safely rely on a specific micro version of the API never to change the request and response semantics. Read more about API Microversions to understand how stability and backwards compatibility are maintained.

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