/usr/share/pyshared/melange/openstack/common/extensions.py is in python-melange 1:2012.1-3.
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# Copyright 2011 OpenStack LLC.
# 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 imp
import os
import routes
import webob.dec
import webob.exc
import logging
from lxml import etree
from melange.openstack.common import exception
from melange.openstack.common import wsgi
LOG = logging.getLogger('extensions')
DEFAULT_XMLNS = "http://docs.openstack.org/"
XMLNS_ATOM = "http://www.w3.org/2005/Atom"
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.
"""
def get_name(self):
"""The name of the extension.
e.g. 'Fox In Socks'
"""
raise NotImplementedError()
def get_alias(self):
"""The alias for the extension.
e.g. 'FOXNSOX'
"""
raise NotImplementedError()
def get_description(self):
"""Friendly description for the extension.
e.g. 'The Fox In Socks Extension'
"""
raise NotImplementedError()
def get_namespace(self):
"""The XML namespace for the extension.
e.g. 'http://www.fox.in.socks/api/ext/pie/v1.0'
"""
raise NotImplementedError()
def get_updated(self):
"""The timestamp when the extension was last updated.
e.g. '2011-01-22T13:25:27-06:00'
"""
# NOTE(justinsb): Not sure of the purpose of this is, vs the XML NS
raise NotImplementedError()
def get_resources(self):
"""List of extensions.ResourceExtension extension objects.
Resources define new nouns, and are accessible through URLs.
"""
resources = []
return resources
def get_actions(self):
"""List of extensions.ActionExtension extension objects.
Actions are verbs callable from the API.
"""
actions = []
return actions
def get_request_extensions(self):
"""List of extensions.RequestException extension objects.
Request extensions are used to handle custom request data.
"""
request_exts = []
return request_exts
class ActionExtensionController(object):
def __init__(self, application):
self.application = application
self.action_handlers = {}
def add_action(self, action_name, handler):
self.action_handlers[action_name] = handler
def action(self, req, id, body):
for action_name, handler in self.action_handlers.iteritems():
if action_name in body:
return handler(body, req, id)
# no action handler found (bump to downstream application)
res = self.application
return res
class ActionExtensionResource(wsgi.Resource):
def __init__(self, application):
controller = ActionExtensionController(application)
wsgi.Resource.__init__(self, controller)
def add_action(self, action_name, handler):
self.controller.add_action(action_name, handler)
class RequestExtensionController(object):
def __init__(self, application):
self.application = application
self.handlers = []
def add_handler(self, handler):
self.handlers.append(handler)
def process(self, req, *args, **kwargs):
res = req.get_response(self.application)
# currently request handlers are un-ordered
for handler in self.handlers:
res = handler(req, res)
return res
class RequestExtensionResource(wsgi.Resource):
def __init__(self, application):
controller = RequestExtensionController(application)
wsgi.Resource.__init__(self, controller)
def add_handler(self, handler):
self.controller.add_handler(handler)
class ExtensionsResource(wsgi.Resource):
def __init__(self, extension_manager):
self.extension_manager = extension_manager
body_serializers = {'application/xml': ExtensionsXMLSerializer()}
serializer = wsgi.ResponseSerializer(body_serializers=body_serializers)
super(ExtensionsResource, self).__init__(self, None, serializer)
def _translate(self, ext):
ext_data = {}
ext_data['name'] = ext.get_name()
ext_data['alias'] = ext.get_alias()
ext_data['description'] = ext.get_description()
ext_data['namespace'] = ext.get_namespace()
ext_data['updated'] = ext.get_updated()
ext_data['links'] = [] # TODO(dprince): implement extension links
return ext_data
def index(self, req):
extensions = []
for _alias, ext in self.extension_manager.extensions.iteritems():
extensions.append(self._translate(ext))
return dict(extensions=extensions)
def show(self, req, id):
# NOTE(dprince): the extensions alias is used as the 'id' for show
ext = self.extension_manager.extensions.get(id, None)
if not ext:
raise webob.exc.HTTPNotFound(
_("Extension with alias %s does not exist") % id)
return dict(extension=self._translate(ext))
def delete(self, req, id):
raise webob.exc.HTTPNotFound()
def create(self, req):
raise webob.exc.HTTPNotFound()
class ExtensionMiddleware(wsgi.Middleware):
"""Extensions middleware for WSGI."""
@classmethod
def factory(cls, global_config, **local_config):
"""Paste factory."""
def _factory(app):
return cls(app, global_config, **local_config)
return _factory
def _action_ext_resources(self, application, ext_mgr, mapper):
"""Return a dict of ActionExtensionResource-s by collection."""
action_resources = {}
for action in ext_mgr.get_actions():
if not action.collection in action_resources.keys():
resource = ActionExtensionResource(application)
mapper.connect("/%s/:(id)/action.:(format)" %
action.collection,
action='action',
controller=resource,
conditions=dict(method=['POST']))
mapper.connect("/%s/:(id)/action" %
action.collection,
action='action',
controller=resource,
conditions=dict(method=['POST']))
action_resources[action.collection] = resource
return action_resources
def _request_ext_resources(self, application, ext_mgr, mapper):
"""Returns a dict of RequestExtensionResource-s by collection."""
request_ext_resources = {}
for req_ext in ext_mgr.get_request_extensions():
if not req_ext.key in request_ext_resources.keys():
resource = RequestExtensionResource(application)
mapper.connect(req_ext.url_route + '.:(format)',
action='process',
controller=resource,
conditions=req_ext.conditions)
mapper.connect(req_ext.url_route,
action='process',
controller=resource,
conditions=req_ext.conditions)
request_ext_resources[req_ext.key] = resource
return request_ext_resources
def __init__(self, application, config, ext_mgr=None):
ext_mgr = ext_mgr or ExtensionManager(
config['api_extensions_path'])
mapper = routes.Mapper()
# extended resources
for resource_ext in ext_mgr.get_resources():
LOG.debug(_('Extended resource: %s'), resource_ext.collection)
controller_resource = wsgi.Resource(resource_ext.controller,
resource_ext.deserializer,
resource_ext.serializer)
self._map_custom_collection_actions(resource_ext, mapper,
controller_resource)
kargs = dict(controller=controller_resource,
collection=resource_ext.collection_actions,
member=resource_ext.member_actions)
if resource_ext.parent:
kargs['parent_resource'] = resource_ext.parent
mapper.resource(resource_ext.collection,
resource_ext.collection, **kargs)
# extended actions
action_resources = self._action_ext_resources(application, ext_mgr,
mapper)
for action in ext_mgr.get_actions():
LOG.debug(_('Extended action: %s'), action.action_name)
resource = action_resources[action.collection]
resource.add_action(action.action_name, action.handler)
# extended requests
req_controllers = self._request_ext_resources(application, ext_mgr,
mapper)
for request_ext in ext_mgr.get_request_extensions():
LOG.debug(_('Extended request: %s'), request_ext.key)
controller = req_controllers[request_ext.key]
controller.add_handler(request_ext.handler)
self._router = routes.middleware.RoutesMiddleware(self._dispatch,
mapper)
super(ExtensionMiddleware, self).__init__(application)
def _map_custom_collection_actions(self, resource_ext, mapper,
controller_resource):
for action, method in resource_ext.collection_actions.iteritems():
parent = resource_ext.parent
conditions = dict(method=[method])
path = "/%s/%s" % (resource_ext.collection, action)
path_prefix = ""
if parent:
path_prefix = "/%s/{%s_id}" % (parent["collection_name"],
parent["member_name"])
with mapper.submapper(controller=controller_resource,
action=action,
path_prefix=path_prefix,
conditions=conditions) as submap:
submap.connect(path)
submap.connect("%s.:(format)" % path)
@webob.dec.wsgify(RequestClass=wsgi.Request)
def __call__(self, req):
"""Route the incoming request with router."""
req.environ['extended.app'] = self.application
return self._router
@staticmethod
@webob.dec.wsgify(RequestClass=wsgi.Request)
def _dispatch(req):
"""Dispatch the request.
Returns the routed WSGI app's response or defers to the extended
application.
"""
match = req.environ['wsgiorg.routing_args'][1]
if not match:
return req.environ['extended.app']
app = match['controller']
return app
class ExtensionManager(object):
"""Load extensions from the configured extension path.
See nova/tests/api/openstack/extensions/foxinsocks/extension.py for an
example extension implementation.
"""
def __init__(self, path):
LOG.debug(_('Initializing extension manager.'))
self.path = path
self.extensions = {}
self._load_all_extensions()
def get_resources(self):
"""Returns a list of ResourceExtension objects."""
resources = []
extension_resource = ExtensionsResource(self)
res_ext = ResourceExtension('extensions',
extension_resource,
serializer=extension_resource.serializer)
resources.append(res_ext)
for alias, ext in self.extensions.iteritems():
try:
resources.extend(ext.get_resources())
except AttributeError:
# NOTE(dprince): Extension aren't required to have resource
# extensions
pass
return resources
def get_actions(self):
"""Returns a list of ActionExtension objects."""
actions = []
for alias, ext in self.extensions.iteritems():
try:
actions.extend(ext.get_actions())
except AttributeError:
# NOTE(dprince): Extension aren't required to have action
# extensions
pass
return actions
def get_request_extensions(self):
"""Returns a list of RequestExtension objects."""
request_exts = []
for alias, ext in self.extensions.iteritems():
try:
request_exts.extend(ext.get_request_extensions())
except AttributeError:
# NOTE(dprince): Extension aren't required to have request
# extensions
pass
return request_exts
def _check_extension(self, extension):
"""Checks for required methods in extension objects."""
try:
LOG.debug(_('Ext name: %s'), extension.get_name())
LOG.debug(_('Ext alias: %s'), extension.get_alias())
LOG.debug(_('Ext description: %s'), extension.get_description())
LOG.debug(_('Ext namespace: %s'), extension.get_namespace())
LOG.debug(_('Ext updated: %s'), extension.get_updated())
except AttributeError as ex:
LOG.exception(_("Exception loading extension: %s"), unicode(ex))
return False
return True
def _load_all_extensions(self):
"""Load extensions from the configured path.
Load extensions from the configured path. The extension name is
constructed from the module_name. If your extension module was named
widgets.py the extension class within that module should be
'Widgets'.
In addition, extensions are loaded from the 'contrib' directory.
See nova/tests/api/openstack/extensions/foxinsocks.py for an example
extension implementation.
"""
if os.path.exists(self.path):
self._load_all_extensions_from_path(self.path)
contrib_path = os.path.join(os.path.dirname(__file__), "contrib")
if os.path.exists(contrib_path):
self._load_all_extensions_from_path(contrib_path)
def _load_all_extensions_from_path(self, path):
for f in os.listdir(path):
LOG.debug(_('Loading extension file: %s'), f)
mod_name, file_ext = os.path.splitext(os.path.split(f)[-1])
ext_path = os.path.join(path, f)
if file_ext.lower() == '.py' and not mod_name.startswith('_'):
mod = imp.load_source(mod_name, ext_path)
ext_name = mod_name[0].upper() + mod_name[1:]
new_ext_class = getattr(mod, ext_name, None)
if not new_ext_class:
LOG.warn(_('Did not find expected name '
'"%(ext_name)s" in %(file)s'),
{'ext_name': ext_name,
'file': ext_path})
continue
new_ext = new_ext_class()
self.add_extension(new_ext)
def add_extension(self, ext):
# Do nothing if the extension doesn't check out
if not self._check_extension(ext):
return
alias = ext.get_alias()
LOG.debug(_('Loaded extension: %s'), alias)
if alias in self.extensions:
raise exception.Error("Found duplicate extension: %s" % alias)
self.extensions[alias] = ext
class RequestExtension(object):
"""Extend requests and responses of core nova OpenStack API resources.
Provide a way to add data to responses and handle custom request data
that is sent to core nova OpenStack API controllers.
"""
def __init__(self, method, url_route, handler):
self.url_route = url_route
self.handler = handler
self.conditions = dict(method=[method])
self.key = "%s-%s" % (method, url_route)
class ActionExtension(object):
"""Add custom actions to core nova OpenStack API resources."""
def __init__(self, collection, action_name, handler):
self.collection = collection
self.action_name = action_name
self.handler = handler
class ResourceExtension(object):
"""Add top level resources to the OpenStack API in nova."""
def __init__(self, collection, controller, parent=None,
collection_actions=None, member_actions=None,
deserializer=None, serializer=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.deserializer = deserializer
self.serializer = serializer
class ExtensionsXMLSerializer(wsgi.XMLDictSerializer):
def __init__(self):
self.nsmap = {None: DEFAULT_XMLNS, 'atom': XMLNS_ATOM}
def show(self, ext_dict):
ext = etree.Element('extension', nsmap=self.nsmap)
self._populate_ext(ext, ext_dict['extension'])
return self._to_xml(ext)
def index(self, exts_dict):
exts = etree.Element('extensions', nsmap=self.nsmap)
for ext_dict in exts_dict['extensions']:
ext = etree.SubElement(exts, 'extension')
self._populate_ext(ext, ext_dict)
return self._to_xml(exts)
def _populate_ext(self, ext_elem, ext_dict):
"""Populate an extension xml element from a dict."""
ext_elem.set('name', ext_dict['name'])
ext_elem.set('namespace', ext_dict['namespace'])
ext_elem.set('alias', ext_dict['alias'])
ext_elem.set('updated', ext_dict['updated'])
desc = etree.Element('description')
desc.text = ext_dict['description']
ext_elem.append(desc)
for link in ext_dict.get('links', []):
elem = etree.SubElement(ext_elem, '{%s}link' % XMLNS_ATOM)
elem.set('rel', link['rel'])
elem.set('href', link['href'])
elem.set('type', link['type'])
return ext_elem
def _to_xml(self, root):
"""Convert the xml object to an xml string."""
return etree.tostring(root, encoding='UTF-8')
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