OpenStack Block Storage (Cinder)
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# 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.
"""Utility methods for working with WSGI servers."""
import webob.dec
import webob.exc
from cinder.i18n import _
class Request(webob.Request):
pass
class Application(object):
"""Base WSGI application wrapper. Subclasses need to implement __call__."""
@classmethod
def factory(cls, global_config, **local_config):
"""Used for paste app factories in paste.deploy config files.
Any local configuration (that is, values under the [app:APPNAME]
section of the paste config) will be passed into the `__init__` method
as kwargs.
A hypothetical configuration would look like:
[app:wadl]
latest_version = 1.3
paste.app_factory = cinder.api.fancy_api:Wadl.factory
which would result in a call to the `Wadl` class as
import cinder.api.fancy_api
fancy_api.Wadl(latest_version='1.3')
You could of course re-implement the `factory` method in subclasses,
but using the kwarg passing it shouldn't be necessary.
"""
return cls(**local_config)
def __call__(self, environ, start_response):
r"""Subclasses will probably want to implement __call__ like this:
@webob.dec.wsgify(RequestClass=Request)
def __call__(self, req):
# Any of the following objects work as responses:
# Option 1: simple string
res = 'message\n'
# Option 2: a nicely formatted HTTP exception page
res = exc.HTTPForbidden(explanation='Nice try')
# Option 3: a webob Response object (in case you need to play with
# headers, or you want to be treated like an iterable)
res = Response();
res.app_iter = open('somefile')
# Option 4: any wsgi app to be run next
res = self.application
# Option 5: you can get a Response object for a wsgi app, too, to
# play with headers etc
res = req.get_response(self.application)
# You can then just return your response...
return res
# ... or set req.response and return None.
req.response = res
See the end of http://pythonpaste.org/webob/modules/dec.html
for more info.
"""
raise NotImplementedError(_('You must implement __call__'))
class Middleware(Application):
"""Base WSGI middleware.
These classes require an application to be
initialized that will be called next. By default the middleware will
simply call its wrapped app, or you can override __call__ to customize its
behavior.
"""
@classmethod
def factory(cls, global_config, **local_config):
"""Used for paste app factories in paste.deploy config files.
Any local configuration (that is, values under the [filter:APPNAME]
section of the paste config) will be passed into the `__init__` method
as kwargs.
A hypothetical configuration would look like:
[filter:analytics]
redis_host = 127.0.0.1
paste.filter_factory = cinder.api.analytics:Analytics.factory
which would result in a call to the `Analytics` class as
import cinder.api.analytics
analytics.Analytics(app_from_paste, redis_host='127.0.0.1')
You could of course re-implement the `factory` method in subclasses,
but using the kwarg passing it shouldn't be necessary.
"""
def _factory(app):
return cls(app, **local_config)
return _factory
def __init__(self, application):
self.application = application
def process_request(self, req):
"""Called on each request.
If this returns None, the next application down the stack will be
executed. If it returns a response then that response will be returned
and execution will stop here.
"""
return None
def process_response(self, response):
"""Do whatever you'd like to the response."""
return response
@webob.dec.wsgify(RequestClass=Request)
def __call__(self, req):
response = self.process_request(req)
if response:
return response
response = req.get_response(self.application)
return self.process_response(response)