enable xml error message response

return xml error message when Accept:application/xml request received.
default to json response when none specified.

Change-Id: Idd454c5bc76adb583bc0a9afce9f31659e7fe2ac

ceilometer/api/middleware.py

@@ -22,6 +22,12 @@ Based on pecan.middleware.errordocument
 """
 
 import json
+import webob
+from xml import etree as et
+
+from ceilometer.openstack.common import log
+
+LOG = log.getLogger(__name__)
 
 
 class ParsableErrorMiddleware(object):
@@ -61,12 +67,24 @@ class ParsableErrorMiddleware(object):
 
         app_iter = self.app(environ, replacement_start_response)
         if (state['status_code'] / 100) not in (2, 3):
-            # FIXME(dhellmann): Always returns errors as JSON,
+            req = webob.Request(environ)
-            # but should look at the environ to determine
+            if (req.accept.best_match(['application/json', 'application/xml'])
-            # the desired type.
+                == 'application/xml'):
-            body = [json.dumps({'error_message': '\n'.join(app_iter)})]
+                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('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])))
-            state['headers'].append(('Content-Type', 'application/json'))
         else:
             body = app_iter
         return body

tests/api/v2/test_app.py

@@ -26,6 +26,7 @@ from oslo.config import cfg
 from ceilometer.api import app
 from ceilometer.api import acl
 from ceilometer import service
+from .base import FunctionalTest
 
 
 class TestApp(unittest.TestCase):
@@ -50,3 +51,66 @@ class TestApp(unittest.TestCase):
         api_app = app.setup_app()
         self.assertEqual(api_app.auth_protocol, 'barttp')
         os.unlink(tmpfile)
+
+
+class TestApiMiddleware(FunctionalTest):
+
+    def test_json_parsable_error_middleware_404(self):
+        response = self.get_json('/invalid_path',
+                                 expect_errors=True,
+                                 headers={"Accept":
+                                          "application/json"}
+                                 )
+        self.assertEqual(response.status_int, 404)
+        self.assertEqual(response.content_type, "application/json")
+        self.assertTrue(response.json['error_message'])
+        response = self.get_json('/invalid_path',
+                                 expect_errors=True,
+                                 headers={"Accept":
+                                          "application/json,application/xml"}
+                                 )
+        self.assertEqual(response.status_int, 404)
+        self.assertEqual(response.content_type, "application/json")
+        self.assertTrue(response.json['error_message'])
+        response = self.get_json('/invalid_path',
+                                 expect_errors=True,
+                                 headers={"Accept":
+                                          "application/xml;q=0.8, \
+                                          application/json"}
+                                 )
+        self.assertEqual(response.status_int, 404)
+        self.assertEqual(response.content_type, "application/json")
+        self.assertTrue(response.json['error_message'])
+        response = self.get_json('/invalid_path',
+                                 expect_errors=True
+                                 )
+        self.assertEqual(response.status_int, 404)
+        self.assertEqual(response.content_type, "application/json")
+        self.assertTrue(response.json['error_message'])
+        response = self.get_json('/invalid_path',
+                                 expect_errors=True,
+                                 headers={"Accept":
+                                          "text/html,*/*"}
+                                 )
+        self.assertEqual(response.status_int, 404)
+        self.assertEqual(response.content_type, "application/json")
+        self.assertTrue(response.json['error_message'])
+
+    def test_xml_parsable_error_middleware_404(self):
+        response = self.get_json('/invalid_path',
+                                 expect_errors=True,
+                                 headers={"Accept":
+                                          "application/xml,*/*"}
+                                 )
+        self.assertEqual(response.status_int, 404)
+        self.assertEqual(response.content_type, "application/xml")
+        self.assertEqual(response.xml.tag, 'error_message')
+        response = self.get_json('/invalid_path',
+                                 expect_errors=True,
+                                 headers={"Accept":
+                                          "application/json;q=0.8 \
+                                          ,application/xml"}
+                                 )
+        self.assertEqual(response.status_int, 404)
+        self.assertEqual(response.content_type, "application/xml")
+        self.assertEqual(response.xml.tag, 'error_message')