From a3576bbb0c7090b97b0b02c88ffa81915db6290b Mon Sep 17 00:00:00 2001
From: Eoghan Glynn <eglynn@redhat.com>
Date: Tue, 10 Jul 2012 08:16:27 +0100
Subject: [PATCH] Return 413 status on over-quota in the native API.

Related to LP 1021373.

Previously we returned a generic 500 Server Error on an over-quota
conditions, whereas this is arguably more appropriately reported
as a 413 status.

Change-Id: I5c1cdc9db54804c512d60e4179c1faa13516d6f9
---
 nova/api/openstack/__init__.py               | 18 ++++++++++++++----
 nova/exception.py                            |  4 ++++
 nova/tests/api/openstack/compute/test_api.py | 16 ++++++++++++++++
 nova/utils.py                                | 13 +++++++++++++
 4 files changed, 47 insertions(+), 4 deletions(-)

diff --git a/nova/api/openstack/__init__.py b/nova/api/openstack/__init__.py
index 3372d9b5e66..f49c721ffa1 100644
--- a/nova/api/openstack/__init__.py
+++ b/nova/api/openstack/__init__.py
@@ -27,6 +27,7 @@
 from nova.api.openstack import wsgi
 from nova import exception
 from nova.openstack.common import log as logging
+from nova import utils
 from nova import wsgi as base_wsgi
 
 
@@ -36,11 +37,20 @@
 class FaultWrapper(base_wsgi.Middleware):
     """Calls down the middleware stack, making exceptions into faults."""
 
-    def _error(self, inner, req, safe=False):
+    def __init__(self, application):
+        self.status_to_type = {}
+        for clazz in utils.walk_class_hierarchy(webob.exc.HTTPError):
+            self.status_to_type[clazz.code] = clazz
+        super(FaultWrapper, self).__init__(application)
+
+    def _error(self, inner, req, headers=None, status=500, safe=False):
         LOG.exception(_("Caught error: %s"), unicode(inner))
-        msg_dict = dict(url=req.url, status=500)
+        msg_dict = dict(url=req.url, status=status)
         LOG.info(_("%(url)s returned with HTTP %(status)d") % msg_dict)
-        outer = webob.exc.HTTPInternalServerError()
+        outer = self.status_to_type.get(status,
+                                        webob.exc.HTTPInternalServerError)()
+        if headers:
+            outer.headers = headers
         # NOTE(johannes): We leave the explanation empty here on
         # purpose. It could possibly have sensitive information
         # that should not be returned back to the user. See
@@ -58,7 +68,7 @@ def __call__(self, req):
         try:
             return req.get_response(self.application)
         except exception.NovaException as ex:
-            return self._error(ex, req, ex.safe)
+            return self._error(ex, req, ex.headers, ex.code, ex.safe)
         except Exception as ex:
             return self._error(ex, req)
 
diff --git a/nova/exception.py b/nova/exception.py
index ac4f44abfc7..d6fa79043ca 100644
--- a/nova/exception.py
+++ b/nova/exception.py
@@ -129,6 +129,8 @@ class NovaException(Exception):
 
     """
     message = _("An unknown exception occurred.")
+    code = 500
+    headers = {}
     safe = False
 
     def __init__(self, message=None, **kwargs):
@@ -995,6 +997,8 @@ class WillNotSchedule(NovaException):
 
 class QuotaError(NovaException):
     message = _("Quota exceeded") + ": code=%(code)s"
+    code = 413
+    headers = {'Retry-After': 0}
     safe = True
 
 
diff --git a/nova/tests/api/openstack/compute/test_api.py b/nova/tests/api/openstack/compute/test_api.py
index a1dd01be36c..3ef8f969071 100644
--- a/nova/tests/api/openstack/compute/test_api.py
+++ b/nova/tests/api/openstack/compute/test_api.py
@@ -144,6 +144,22 @@ def test_safe_exceptions_are_described_in_faults(self):
     def test_unsafe_exceptions_are_not_described_in_faults(self):
         self._do_test_exception_safety_reflected_in_faults(False)
 
+    def _do_test_exception_mapping(self, exception_type):
+        @webob.dec.wsgify
+        def fail(req):
+            raise exception_type('too many used')
+
+        api = self._wsgi_app(fail)
+        resp = webob.Request.blank('/').get_response(api)
+        self.assertTrue('too many used' in resp.body, resp.body)
+        self.assertEqual(resp.status_int, exception_type.code, resp.body)
+        for (key, value) in exception_type.headers.iteritems():
+            self.assertTrue(key in resp.headers)
+            self.assertEquals(resp.headers[key], value)
+
+    def test_quota_error_mapping(self):
+        self._do_test_exception_mapping(exception.QuotaError)
+
     def test_request_id_in_response(self):
         req = webob.Request.blank('/')
         req.method = 'GET'
diff --git a/nova/utils.py b/nova/utils.py
index 86cbdce1d1c..9cfb6d06da5 100644
--- a/nova/utils.py
+++ b/nova/utils.py
@@ -1238,6 +1238,19 @@ def sys_platform_translate(arch):
     return arch
 
 
+def walk_class_hierarchy(clazz, encountered=None):
+    """Walk class hierarchy, yielding most derived classes first"""
+    if not encountered:
+        encountered = []
+    for subclass in clazz.__subclasses__():
+        if subclass not in encountered:
+            encountered.append(subclass)
+            # drill down to leaves first
+            for subsubclass in walk_class_hierarchy(subclass, encountered):
+                yield subsubclass
+            yield subclass
+
+
 class UndoManager(object):
     """Provides a mechanism to facilitate rolling back a series of actions
     when an exception is raised.