Adds expected_errors decorator for API v3

Adds an expected_errors decorator for v3 API methods which allows
the specification of what exceptions can be raised within the
method. If an unexpected error occurs a 500 is instead returned
which plus a request to file a bug report

Partially implements blueprint v3-api-expected-errors

Change-Id: I5723e576b30b47744394517cdb1ff6bab1d8f78b

4 files changed, 82 insertions, 0 deletions

diff --git a/nova/api/openstack/compute/plugins/v3/fixed_ips.py b/nova/api/openstack/compute/plugins/v3/fixed_ips.py
index e98b830bd..5fa4ae3c2 100644
--- a/nova/api/openstack/compute/plugins/v3/fixed_ips.py
+++ b/nova/api/openstack/compute/plugins/v3/fixed_ips.py
@@ -28,6 +28,7 @@ authorize = extensions.extension_authorizer('compute', 'v3:' + ALIAS)
 
 
 class FixedIPController(object):
+    @extensions.expected_errors(404)
     def show(self, req, id):
         """Return data about the given fixed ip."""
         context = req.environ['nova.context']
@@ -55,6 +56,7 @@ class FixedIPController(object):
 
         return fixed_ip_info
 
+    @extensions.expected_errors((400, 404))
     def action(self, req, id, body):
         context = req.environ['nova.context']
         authorize(context)
diff --git a/nova/api/openstack/compute/plugins/v3/keypairs.py b/nova/api/openstack/compute/plugins/v3/keypairs.py
index bf740641e..ab40b051c 100644
--- a/nova/api/openstack/compute/plugins/v3/keypairs.py
+++ b/nova/api/openstack/compute/plugins/v3/keypairs.py
@@ -55,6 +55,7 @@ class KeypairController(object):
         self.api = compute_api.KeypairAPI()
 
     @wsgi.serializers(xml=KeypairTemplate)
+    @extensions.expected_errors((400, 409, 413))
     def create(self, req, body):
         """
         Create or import keypair.
@@ -100,6 +101,7 @@ class KeypairController(object):
         except exception.KeyPairExists as exc:
             raise webob.exc.HTTPConflict(explanation=exc.format_message())
 
+    @extensions.expected_errors(404)
     def delete(self, req, id):
         """
         Delete a keypair with a given name
@@ -113,6 +115,7 @@ class KeypairController(object):
         return webob.Response(status_int=202)
 
     @wsgi.serializers(xml=KeypairTemplate)
+    @extensions.expected_errors(404)
     def show(self, req, id):
         """Return data for the given key name."""
         context = req.environ['nova.context']
diff --git a/nova/api/openstack/extensions.py b/nova/api/openstack/extensions.py
index 6cbc5bb78..6fea5d35e 100644
--- a/nova/api/openstack/extensions.py
+++ b/nova/api/openstack/extensions.py
@@ -17,6 +17,7 @@
 #    under the License.
 
 import abc
+import functools
 import os
 
 import webob.dec
@@ -451,3 +452,42 @@ class V3APIExtensionBase(object):
     def version(self):
         """Version of the extension."""
         pass
+
+
+def expected_errors(errors):
+    """Decorator for v3 API methods which specifies expected exceptions.
+
+    Specify which exceptions may occur when an API method is called. If an
+    unexpected exception occurs then return a 500 instead and ask the user
+    of the API to file a bug report.
+    """
+    def decorator(f):
+        @functools.wraps(f)
+        def wrapped(*args, **kwargs):
+            try:
+                return f(*args, **kwargs)
+            except Exception as exc:
+                if isinstance(exc, webob.exc.WSGIHTTPException):
+                    if isinstance(errors, int):
+                        t_errors = (errors,)
+                    else:
+                        t_errors = errors
+                    if exc.code in t_errors:
+                        raise
+                elif isinstance(exc, exception.PolicyNotAuthorized):
+                    # Note(cyeoh): Special case to handle
+                    # PolicyNotAuthorized exceptions so every
+                    # extension method does not need to wrap authorize
+                    # calls. ResourceExceptionHandler silently
+                    # converts NotAuthorized to HTTPForbidden
+                    raise
+
+                LOG.exception(_("Unexpected exception in API method"))
+                msg = _('Unexpected API Error. Please report this at '
+                    'http://bugs.launchpad.net/nova/ and attach the Nova '
+                    'API log if possible.\n%s') % type(exc)
+                raise webob.exc.HTTPInternalServerError(explanation=msg)
+
+        return wrapped
+
+    return decorator
diff --git a/nova/tests/api/openstack/compute/test_v3_extensions.py b/nova/tests/api/openstack/compute/test_v3_extensions.py
index 97429ca45..ec472f38a 100644
--- a/nova/tests/api/openstack/compute/test_v3_extensions.py
+++ b/nova/tests/api/openstack/compute/test_v3_extensions.py
@@ -16,10 +16,12 @@
 
 from oslo.config import cfg
 import stevedore
+import webob.exc
 
 from nova.api import openstack
 from nova.api.openstack import compute
 from nova.api.openstack.compute import plugins
+from nova.api.openstack import extensions
 from nova import exception
 from nova import test
 
@@ -139,3 +141,38 @@ class ExtensionLoadingTestCase(test.TestCase):
         self.stubs.Set(plugins, 'LoadedExtensionInfo',
                        fake_loaded_extension_info)
         self.assertRaises(exception.CoreAPIMissing, compute.APIRouterV3)
+
+    def test_extensions_expected_error(self):
+        @extensions.expected_errors(404)
+        def fake_func():
+            raise webob.exc.HTTPNotFound()
+
+        self.assertRaises(webob.exc.HTTPNotFound, fake_func)
+
+    def test_extensions_expected_error_from_list(self):
+        @extensions.expected_errors((404, 403))
+        def fake_func():
+            raise webob.exc.HTTPNotFound()
+
+        self.assertRaises(webob.exc.HTTPNotFound, fake_func)
+
+    def test_extensions_unexpected_error(self):
+        @extensions.expected_errors(404)
+        def fake_func():
+            raise webob.exc.HTTPConflict()
+
+        self.assertRaises(webob.exc.HTTPInternalServerError, fake_func)
+
+    def test_extensions_unexpected_error_from_list(self):
+        @extensions.expected_errors((404, 413))
+        def fake_func():
+            raise webob.exc.HTTPConflict()
+
+        self.assertRaises(webob.exc.HTTPInternalServerError, fake_func)
+
+    def test_extensions_unexpected_policy_not_authorized_error(self):
+        @extensions.expected_errors(404)
+        def fake_func():
+            raise exception.PolicyNotAuthorized(action="foo")
+
+        self.assertRaises(exception.PolicyNotAuthorized, fake_func)