Port parsable error middleware from Ironic

Partial-Bug: 1411871
Change-Id: Ibe67d06f0d3a685dc08b896d466dfa94513c5d10

magnum/api/app.py

@@ -15,6 +15,7 @@ import pecan
 
 from magnum.api import auth
 from magnum.api import config as api_config
+from magnum.api import middleware
 
 # Register options for the service
 API_SERVICE_OPTS = [
@@ -52,6 +53,7 @@ def setup_app(config=None):
     app = pecan.make_app(
         app_conf.pop('root'),
         logging=getattr(config, 'logging', {}),
+        wrap_app=middleware.ParsableErrorMiddleware,
         **app_conf
     )
 

magnum/api/middleware/__init__.py

@@ -13,8 +13,11 @@
 # under the License.
 
 from magnum.api.middleware import auth_token
+from magnum.api.middleware import parsable_error
 
 
 AuthTokenMiddleware = auth_token.AuthTokenMiddleware
+ParsableErrorMiddleware = parsable_error.ParsableErrorMiddleware
 
-__all__ = (AuthTokenMiddleware)
+__all__ = (AuthTokenMiddleware,
+           ParsableErrorMiddleware)

magnum/api/middleware/parsable_error.py

@@ -0,0 +1,91 @@
+# -*- encoding: utf-8 -*-
+#
+# Copyright ? 2012 New Dream Network, LLC (DreamHost)
+#
+# Author: Doug Hellmann <doug.hellmann@dreamhost.com>
+#
+# 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.
+"""
+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 xml import etree as et
+
+import webob
+
+from magnum.openstack.common._i18n import _
+from magnum.openstack.common._i18n import _LE
+from magnum.openstack.common import log
+
+LOG = log.getLogger(__name__)
+
+
+class ParsableErrorMiddleware(object):
+    """Replace error body with something the client can parse."""
+    def __init__(self, app):
+        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)
+
+        app_iter = self.app(environ, replacement_start_response)
+        if (state['status_code'] // 100) not in (2, 3):
+            req = webob.Request(environ)
+            if (req.accept.best_match(['application/json', 'application/xml'])
+                == 'application/xml'):
+                try:
+                    # simple check xml is valid
+                    body = [et.ElementTree.tostring(
+                            et.ElementTree.fromstring('<error_message>'
+                                                      + '\n'.join(app_iter)
+                                                      + '</error_message>'))]
+                except et.ElementTree.ParseError as err:
+                    LOG.error(_LE('Error parsing HTTP response: %s'), err)
+                    body = ['<error_message>%s' % state['status_code']
+                            + '</error_message>']
+                state['headers'].append(('Content-Type', 'application/xml'))
+            else:
+                body = [json.dumps({'error_message': '\n'.join(app_iter)})]
+                state['headers'].append(('Content-Type', 'application/json'))
+            state['headers'].append(('Content-Length', len(body[0])))
+        else:
+            body = app_iter
+        return body

magnum/tests/api/controllers/v1/test_baymodel.py

@@ -136,7 +136,7 @@ class TestPatch(api_base.FunctionalTest):
                                    expect_errors=True)
         self.assertEqual(404, response.status_int)
         self.assertEqual('application/json', response.content_type)
-        self.assertTrue(response.json['faultstring'])
+        self.assertTrue(response.json['error_message'])
 
     @mock.patch.object(timeutils, 'utcnow')
     def test_replace_singular(self, mock_utcnow):
@@ -185,7 +185,7 @@ class TestPatch(api_base.FunctionalTest):
                              expect_errors=True)
         self.assertEqual('application/json', response.content_type)
         self.assertEqual(400, response.status_code)
-        self.assertTrue(response.json['faultstring'])
+        self.assertTrue(response.json['error_message'])
 
     def test_add_root(self):
         name = 'bay_model_example_B'
@@ -208,7 +208,7 @@ class TestPatch(api_base.FunctionalTest):
                             expect_errors=True)
         self.assertEqual('application/json', response.content_type)
         self.assertEqual(400, response.status_int)
-        self.assertTrue(response.json['faultstring'])
+        self.assertTrue(response.json['error_message'])
 
     def test_add_multi(self):
         json = [
@@ -241,7 +241,7 @@ class TestPatch(api_base.FunctionalTest):
                                    expect_errors=True)
         self.assertEqual(400, response.status_int)
         self.assertEqual('application/json', response.content_type)
-        self.assertTrue(response.json['faultstring'])
+        self.assertTrue(response.json['error_message'])
 
 
 class TestPost(api_base.FunctionalTest):
@@ -297,7 +297,7 @@ class TestDelete(api_base.FunctionalTest):
                                  expect_errors=True)
         self.assertEqual(404, response.status_int)
         self.assertEqual('application/json', response.content_type)
-        self.assertTrue(response.json['faultstring'])
+        self.assertTrue(response.json['error_message'])
 
     def test_delete_baymodel_with_bay(self):
         baymodel = obj_utils.create_test_baymodel(self.context)
@@ -306,12 +306,12 @@ class TestDelete(api_base.FunctionalTest):
                                expect_errors=True)
         self.assertEqual(400, response.status_int)
         self.assertEqual('application/json', response.content_type)
-        self.assertTrue(response.json['faultstring'])
-        self.assertIn(baymodel.uuid, response.json['faultstring'])
+        self.assertTrue(response.json['error_message'])
+        self.assertIn(baymodel.uuid, response.json['error_message'])
 
     def test_delete_baymodel_not_found(self):
         uuid = utils.generate_uuid()
         response = self.delete('/baymodels/%s' % uuid, expect_errors=True)
         self.assertEqual(404, response.status_int)
         self.assertEqual('application/json', response.content_type)
-        self.assertTrue(response.json['faultstring'])
+        self.assertTrue(response.json['error_message'])