102 lines
4.3 KiB
ReStructuredText
102 lines
4.3 KiB
ReStructuredText
How the SDK is organized
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========================
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The following diagram shows how the project is laid out.
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.. literalinclude:: layout.txt
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Resource
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--------
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The :class:`openstack.resource.Resource` base class is the building block
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of any service implementation. ``Resource`` objects correspond to the
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resources each service's REST API works with, so the
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:class:`openstack.compute.v2.server.Server` subclass maps to the compute
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service's ``https://openstack:1234/v2/servers`` resource.
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The base ``Resource`` contains methods to support the typical
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`CRUD <http://en.wikipedia.org/wiki/Create,_read,_update_and_delete>`_
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operations supported by REST APIs, and handles the construction of URLs
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and calling the appropriate HTTP verb on the given ``Adapter``.
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Values sent to or returned from the service are implemented as attributes
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on the ``Resource`` subclass with type :class:`openstack.resource.prop`.
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The ``prop`` is created with the exact name of what the API expects,
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and can optionally include a ``type`` to be validated against on requests.
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You should choose an attribute name that follows PEP-8, regardless of what
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the server-side expects, as this ``prop`` becomes a mapping between the two.::
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is_public = resource.prop('os-flavor-access:is_public', type=bool)
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There are six additional attributes which the ``Resource`` class checks
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before making requests to the REST API. ``allow_create``, ``allow_retreive``,
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``allow_commit``, ``allow_delete``, ``allow_head``, and ``allow_list`` are set
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to ``True`` or ``False``, and are checked before making the corresponding
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method call.
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The ``base_path`` attribute should be set to the URL which corresponds to
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this resource. Many ``base_path``\s are simple, such as ``"/servers"``.
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For ``base_path``\s which are composed of non-static information, Python's
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string replacement is used, e.g., ``base_path = "/servers/%(server_id)s/ips"``.
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``resource_key`` and ``resources_key`` are attributes to set when a
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``Resource`` returns more than one item in a response, or otherwise
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requires a key to obtain the response value. For example, the ``Server``
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class sets ``resource_key = "server"`` as an individual ``Server`` is
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stored in a dictionary keyed with the singular noun,
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and ``resource_keys = "servers"`` as multiple ``Server``\s are stored in
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a dictionary keyed with the plural noun in the response.
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Proxy
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-----
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Each service implements a ``Proxy`` class based on
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:class:`~openstack.proxy.Proxy`, within the
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``openstack/<program_name>/vX/_proxy.py`` module. For example, the v2 compute
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service's ``Proxy`` exists in ``openstack/compute/v2/_proxy.py``.
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The :class:`~openstack.proxy.Proxy` class is based on
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:class:`~keystoneauth1.adapter.Adapter`.
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.. autoclass:: openstack.proxy.Proxy
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:members:
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:show-inheritance:
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Each service's ``Proxy`` provides a higher-level interface for users to work
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with via a :class:`~openstack.connection.Connection` instance.
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Rather than requiring users to maintain their own ``Adapter`` and work with
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lower-level :class:`~openstack.resource.Resource` objects, the ``Proxy``
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interface offers a place to make things easier for the caller.
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Each ``Proxy`` class implements methods which act on the underlying
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``Resource`` classes which represent the service. For example::
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def list_flavors(self, **params):
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return flavor.Flavor.list(self.session, **params)
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This method is operating on the ``openstack.compute.v2.flavor.Flavor.list``
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method. For the time being, it simply passes on the ``Adapter`` maintained
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by the ``Proxy``, and returns what the underlying ``Resource.list`` method
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does.
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The implementations and method signatures of ``Proxy`` methods are currently
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under construction, as we figure out the best way to implement them in a
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way which will apply nicely across all of the services.
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Connection
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----------
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The :class:`openstack.connection.Connection` class builds atop a
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:class:`openstack.config.cloud_region.CloudRegion` object, and provides a
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higher level interface constructed of ``Proxy`` objects from each of the
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services.
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The ``Connection`` class' primary purpose is to act as a high-level interface
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to this SDK, managing the lower level connecton bits and exposing the
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``Resource`` objects through their corresponding `Proxy`_ object.
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If you've built proper ``Resource`` objects and implemented methods on the
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corresponding ``Proxy`` object, the high-level interface to your service
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should now be exposed.
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