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extensions.py
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extensions.py
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# Copyright 2011 OpenStack Foundation
# Copyright 2011 Justin Santa Barbara
# All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import abc
import functools
from oslo_log import log as logging
from oslo_utils import importutils
import six
import webob.dec
import webob.exc
from nova.api.openstack import wsgi
from nova import exception
from nova.i18n import _
from nova.i18n import _LE
from nova.i18n import _LW
LOG = logging.getLogger(__name__)
class ExtensionDescriptor(object):
"""Base class that defines the contract for extensions.
Note that you don't have to derive from this class to have a valid
extension; it is purely a convenience.
"""
# The name of the extension, e.g., 'Fox In Socks'
name = None
# The alias for the extension, e.g., 'FOXNSOX'
alias = None
# Description comes from the docstring for the class
# The timestamp when the extension was last updated, e.g.,
# '2011-01-22T19:25:27Z'
updated = None
def __init__(self, ext_mgr):
"""Register extension with the extension manager."""
ext_mgr.register(self)
self.ext_mgr = ext_mgr
def get_resources(self):
"""List of extensions.ResourceExtension extension objects.
Resources define new nouns, and are accessible through URLs.
"""
resources = []
return resources
def get_controller_extensions(self):
"""List of extensions.ControllerExtension extension objects.
Controller extensions are used to extend existing controllers.
"""
controller_exts = []
return controller_exts
def __repr__(self):
return "<Extension: name=%s, alias=%s, updated=%s>" % (
self.name, self.alias, self.updated)
def is_valid(self):
"""Validate required fields for extensions.
Raises an attribute error if the attr is not defined
"""
for attr in ('name', 'alias', 'updated', 'namespace'):
if getattr(self, attr) is None:
raise AttributeError("%s is None, needs to be defined" % attr)
return True
class ExtensionsController(wsgi.Resource):
def __init__(self, extension_manager):
self.extension_manager = extension_manager
super(ExtensionsController, self).__init__(None)
def _translate(self, ext):
ext_data = {}
ext_data['name'] = ext.name
ext_data['alias'] = ext.alias
ext_data['description'] = ext.__doc__
ext_data['namespace'] = ext.namespace
ext_data['updated'] = ext.updated
ext_data['links'] = [] # TODO(dprince): implement extension links
return ext_data
def index(self, req):
extensions = []
for ext in self.extension_manager.sorted_extensions():
extensions.append(self._translate(ext))
return dict(extensions=extensions)
def show(self, req, id):
try:
# NOTE(dprince): the extensions alias is used as the 'id' for show
ext = self.extension_manager.extensions[id]
except KeyError:
raise webob.exc.HTTPNotFound()
return dict(extension=self._translate(ext))
def delete(self, req, id):
raise webob.exc.HTTPNotFound()
def create(self, req, body):
raise webob.exc.HTTPNotFound()
class ExtensionManager(object):
"""Load extensions from the configured extension path.
See nova/tests/api/openstack/compute/extensions/foxinsocks.py or an
example extension implementation.
"""
def sorted_extensions(self):
if self.sorted_ext_list is None:
self.sorted_ext_list = sorted(six.iteritems(self.extensions))
for _alias, ext in self.sorted_ext_list:
yield ext
def is_loaded(self, alias):
return alias in self.extensions
def register(self, ext):
# Do nothing if the extension doesn't check out
if not self._check_extension(ext):
return
alias = ext.alias
if alias in self.extensions:
raise exception.NovaException("Found duplicate extension: %s"
% alias)
self.extensions[alias] = ext
self.sorted_ext_list = None
def get_resources(self):
"""Returns a list of ResourceExtension objects."""
resources = []
resources.append(ResourceExtension('extensions',
ExtensionsController(self)))
for ext in self.sorted_extensions():
try:
resources.extend(ext.get_resources())
except AttributeError:
# NOTE(dprince): Extension aren't required to have resource
# extensions
pass
return resources
def get_controller_extensions(self):
"""Returns a list of ControllerExtension objects."""
controller_exts = []
for ext in self.sorted_extensions():
try:
get_ext_method = ext.get_controller_extensions
except AttributeError:
# NOTE(Vek): Extensions aren't required to have
# controller extensions
continue
controller_exts.extend(get_ext_method())
return controller_exts
def _check_extension(self, extension):
"""Checks for required methods in extension objects."""
try:
extension.is_valid()
except AttributeError:
LOG.exception(_LE("Exception loading extension"))
return False
return True
def load_extension(self, ext_factory):
"""Execute an extension factory.
Loads an extension. The 'ext_factory' is the name of a
callable that will be imported and called with one
argument--the extension manager. The factory callable is
expected to call the register() method at least once.
"""
LOG.debug("Loading extension %s", ext_factory)
if isinstance(ext_factory, six.string_types):
# Load the factory
factory = importutils.import_class(ext_factory)
else:
factory = ext_factory
# Call it
LOG.debug("Calling extension factory %s", ext_factory)
factory(self)
def _load_extensions(self):
"""Load extensions specified on the command line."""
extensions = list(self.cls_list)
for ext_factory in extensions:
try:
self.load_extension(ext_factory)
except Exception as exc:
LOG.warning(_LW('Failed to load extension %(ext_factory)s: '
'%(exc)s'),
{'ext_factory': ext_factory, 'exc': exc})
class ControllerExtension(object):
"""Extend core controllers of nova OpenStack API.
Provide a way to extend existing nova OpenStack API core
controllers.
"""
def __init__(self, extension, collection, controller):
self.extension = extension
self.collection = collection
self.controller = controller
class ResourceExtension(object):
"""Add top level resources to the OpenStack API in nova."""
def __init__(self, collection, controller=None, parent=None,
collection_actions=None, member_actions=None,
custom_routes_fn=None, inherits=None, member_name=None):
if not collection_actions:
collection_actions = {}
if not member_actions:
member_actions = {}
self.collection = collection
self.controller = controller
self.parent = parent
self.collection_actions = collection_actions
self.member_actions = member_actions
self.custom_routes_fn = custom_routes_fn
self.inherits = inherits
self.member_name = member_name
@six.add_metaclass(abc.ABCMeta)
class V21APIExtensionBase(object):
"""Abstract base class for all v2.1 API extensions.
All v2.1 API extensions must derive from this class and implement
the abstract methods get_resources and get_controller_extensions
even if they just return an empty list. The extensions must also
define the abstract properties.
"""
def __init__(self, extension_info):
self.extension_info = extension_info
@abc.abstractmethod
def get_resources(self):
"""Return a list of resources extensions.
The extensions should return a list of ResourceExtension
objects. This list may be empty.
"""
pass
@abc.abstractmethod
def get_controller_extensions(self):
"""Return a list of controller extensions.
The extensions should return a list of ControllerExtension
objects. This list may be empty.
"""
pass
@abc.abstractproperty
def name(self):
"""Name of the extension."""
pass
@abc.abstractproperty
def alias(self):
"""Alias for the extension."""
pass
@abc.abstractproperty
def version(self):
"""Version of the extension."""
pass
def __repr__(self):
return "<Extension: name=%s, alias=%s, version=%s>" % (
self.name, self.alias, self.version)
def is_valid(self):
"""Validate required fields for extensions.
Raises an attribute error if the attr is not defined
"""
for attr in ('name', 'alias', 'version'):
if getattr(self, attr) is None:
raise AttributeError("%s is None, needs to be defined" % attr)
return True
def expected_errors(errors):
"""Decorator for v2.1 API methods which specifies expected exceptions.
Specify which exceptions may occur when an API method is called. If an
unexpected exception occurs then return a 500 instead and ask the user
of the API to file a bug report.
"""
def decorator(f):
@functools.wraps(f)
def wrapped(*args, **kwargs):
try:
return f(*args, **kwargs)
except Exception as exc:
if isinstance(exc, webob.exc.WSGIHTTPException):
if isinstance(errors, int):
t_errors = (errors,)
else:
t_errors = errors
if exc.code in t_errors:
raise
elif isinstance(exc, exception.Forbidden):
# Note(cyeoh): Special case to handle
# Forbidden exceptions so every
# extension method does not need to wrap authorize
# calls. ResourceExceptionHandler silently
# converts NotAuthorized to HTTPForbidden
raise
elif isinstance(exc, exception.ValidationError):
# Note(oomichi): Handle a validation error, which
# happens due to invalid API parameters, as an
# expected error.
raise
LOG.exception(_LE("Unexpected exception in API method"))
msg = _('Unexpected API Error. Please report this at '
'http://bugs.launchpad.net/nova/ and attach the Nova '
'API log if possible.\n%s') % type(exc)
raise webob.exc.HTTPInternalServerError(explanation=msg)
return wrapped
return decorator