Source code for ironic.api.middleware.parsable_error

# -*- encoding: utf-8 -*-
# Copyright © 2012 New Dream Network, LLC (DreamHost)
# 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
# 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.
Middleware to replace the plain text message body of an error
response with one formatted so the client can parse it.

Based on pecan.middleware.errordocument

import json

from oslo_log import log

from ironic.common.i18n import _

LOG = log.getLogger(__name__)

[docs] class ParsableErrorMiddleware(object): """Replace error body with something the client can parse.""" def __init__(self, app): = app def __call__(self, environ, start_response): # Request for this state, modified by replace_start_response() # and used when an error is being reported. state = {} def replacement_start_response(status, headers, exc_info=None): """Overrides the default response to make errors parsable.""" try: status_code = int(status.split(' ')[0]) state['status_code'] = status_code except (ValueError, TypeError): # pragma: nocover raise Exception(_( 'ErrorDocumentMiddleware received an invalid ' 'status %s') % status) else: if (state['status_code'] // 100) not in (2, 3): # Remove some headers so we can replace them later # when we have the full error message and can # compute the length. headers = [(h, v) for (h, v) in headers if h not in ('Content-Length', 'Content-Type') ] # Save the headers in case we need to modify them. state['headers'] = headers return start_response(status, headers, exc_info) # The default for ironic is application/json. However, Pecan will try # to output HTML errors if no Accept header is provided. if 'HTTP_ACCEPT' not in environ or environ['HTTP_ACCEPT'] == '*/*': environ['HTTP_ACCEPT'] = 'application/json' app_iter =, replacement_start_response) if (state['status_code'] // 100) not in (2, 3): app_iter = [i.decode('utf-8') for i in app_iter] body = [json.dumps({'error_message': '\n'.join(app_iter)})] body = [item.encode('utf-8') for item in body] state['headers'].append(('Content-Type', 'application/json')) state['headers'].append(('Content-Length', str(len(body[0])))) else: body = app_iter return body