88 lines
3.6 KiB
Python
88 lines
3.6 KiB
Python
# Copyright ? 2012 New Dream Network, LLC (DreamHost)
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""
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Middleware to replace the plain text message body of an error
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response with one formatted so the client can parse it.
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Based on pecan.middleware.errordocument
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"""
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import json
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from xml import etree as et
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from oslo_log import log
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import webob
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from magnum.i18n import _
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from magnum.i18n import _LE
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LOG = log.getLogger(__name__)
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class ParsableErrorMiddleware(object):
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"""Replace error body with something the client can parse."""
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def __init__(self, app):
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self.app = app
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def __call__(self, environ, start_response):
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# Request for this state, modified by replace_start_response()
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# and used when an error is being reported.
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state = {}
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def replacement_start_response(status, headers, exc_info=None):
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"""Overrides the default response to make errors parsable."""
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try:
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status_code = int(status.split(' ')[0])
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state['status_code'] = status_code
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except (ValueError, TypeError): # pragma: nocover
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raise Exception(_(
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'ErrorDocumentMiddleware received an invalid '
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'status %s') % status)
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else:
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if (state['status_code'] // 100) not in (2, 3):
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# Remove some headers so we can replace them later
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# when we have the full error message and can
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# compute the length.
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headers = [(h, v)
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for (h, v) in headers
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if h not in ('Content-Length', 'Content-Type')
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]
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# Save the headers in case we need to modify them.
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state['headers'] = headers
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return start_response(status, headers, exc_info)
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app_iter = self.app(environ, replacement_start_response)
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if (state['status_code'] // 100) not in (2, 3):
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req = webob.Request(environ)
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if (req.accept.best_match(['application/json', 'application/xml'])
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== 'application/xml'):
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try:
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# simple check xml is valid
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body = [et.ElementTree.tostring(
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et.ElementTree.fromstring('<error_message>'
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+ '\n'.join(app_iter)
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+ '</error_message>'))]
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except et.ElementTree.ParseError as err:
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LOG.error(_LE('Error parsing HTTP response: %s'), err)
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body = ['<error_message>%s' % state['status_code']
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+ '</error_message>']
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state['headers'].append(('Content-Type', 'application/xml'))
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else:
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body = [json.dumps({'error_message': '\n'.join(app_iter)})]
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state['headers'].append(('Content-Type', 'application/json'))
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state['headers'].append(('Content-Length', len(body[0])))
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else:
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body = app_iter
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return body
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