Capture exceptions happening in API layer

Added the faulwrapper around EC2 api so that it captures any unseen
exceptions and return a graceful error back. Also changed the openstack
exception message. The actual exception message will be printed in the
logs and would not return back the user.
Removed openstack wsgi dependency from
EC2 fault wrapper. Added unit tests for
EC2 fault wrapper
Fixes bug 869132.

Change-Id: I03d18f321f141ae96f1add99ea0b70e736253c89

etc/nova/api-paste.ini

@@ -18,20 +18,23 @@ use = egg:Paste#urlmap
 /2009-04-04: ec2metadata
 
 [pipeline:ec2cloud]
-pipeline = logrequest ec2noauth cloudrequest authorizer ec2executor
+pipeline = ec2faultwrap logrequest ec2noauth cloudrequest authorizer ec2executor
 # NOTE(vish): use the following pipeline for deprecated auth
-#pipeline = logrequest authenticate cloudrequest authorizer ec2executor
+#pipeline = ec2faultwrap logrequest authenticate cloudrequest authorizer ec2executor
 
 [pipeline:ec2admin]
-pipeline = logrequest ec2noauth adminrequest authorizer ec2executor
+pipeline = ec2faultwrap logrequest ec2noauth adminrequest authorizer ec2executor
 # NOTE(vish): use the following pipeline for deprecated auth
-#pipeline = logrequest authenticate adminrequest authorizer ec2executor
+#pipeline = ec2faultwrap logrequest authenticate adminrequest authorizer ec2executor
 
 [pipeline:ec2metadata]
-pipeline = logrequest ec2md
+pipeline = ec2faultwrap logrequest ec2md
 
 [pipeline:ec2versions]
-pipeline = logrequest ec2ver
+pipeline = ec2faultwrap logrequest ec2ver
+
+[filter:ec2faultwrap]
+paste.filter_factory = nova.api.ec2:FaultWrapper.factory
 
 [filter:logrequest]
 paste.filter_factory = nova.api.ec2:RequestLogging.factory

nova/api/ec2/__init__.py

@@ -36,6 +36,7 @@
 from nova import wsgi
 from nova.api.ec2 import apirequest
 from nova.api.ec2 import ec2utils
+from nova.api.ec2 import faults
 from nova.auth import manager
 
 FLAGS = flags.FLAGS
@@ -49,6 +50,19 @@
 flags.DECLARE('use_forwarded_for', 'nova.api.auth')
 
 
+## Fault Wrapper around all EC2 requests ##
+class FaultWrapper(wsgi.Middleware):
+    """Calls the middleware stack, captures any exceptions into faults."""
+
+    @webob.dec.wsgify(RequestClass=wsgi.Request)
+    def __call__(self, req):
+        try:
+            return req.get_response(self.application)
+        except Exception as ex:
+            LOG.exception(_("FaultWrapper: %s"), unicode(ex))
+            return faults.Fault(webob.exc.HTTPInternalServerError())
+
+
 class RequestLogging(wsgi.Middleware):
     """Access-Log akin logging for all EC2 API requests."""
 

nova/api/ec2/faults.py

@@ -0,0 +1,64 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    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.
+
+import webob.dec
+import webob.exc
+
+from nova import utils
+from nova import context
+from nova import flags
+
+FLAGS = flags.FLAGS
+
+
+class Fault(webob.exc.HTTPException):
+    """Captures exception and return REST Response."""
+
+    def __init__(self, exception):
+        """Create a response for the given webob.exc.exception."""
+        self.wrapped_exc = exception
+
+    @webob.dec.wsgify
+    def __call__(self, req):
+        """Generate a WSGI response based on the exception passed to ctor."""
+        code = self.wrapped_exc.status_int
+        message = self.wrapped_exc.explanation
+
+        if code == 501:
+            message = "The requested function is not supported"
+        code = str(code)
+
+        if 'AWSAccessKeyId' not in req.params:
+            raise webob.exc.HTTPBadRequest()
+        user_id, _sep, project_id = req.params['AWSAccessKeyId'].partition(':')
+        project_id = project_id or user_id
+        remote_address = getattr(req, 'remote_address', '127.0.0.1')
+        if FLAGS.use_forwarded_for:
+            remote_address = req.headers.get('X-Forwarded-For', remote_address)
+
+        ctxt = context.RequestContext(user_id,
+                                      project_id,
+                                      remote_address=remote_address)
+
+        resp = webob.Response()
+        resp.status = self.wrapped_exc.status_int
+        resp.headers['Content-Type'] = 'text/xml'
+        resp.body = str('<?xml version="1.0"?>\n'
+                         '<Response><Errors><Error><Code>%s</Code>'
+                         '<Message>%s</Message></Error></Errors>'
+                         '<RequestID>%s</RequestID></Response>' %
+                         (utils.utf8(code), utils.utf8(message),
+                         utils.utf8(ctxt.request_id)))
+
+        return resp

nova/tests/api/ec2/test_faults.py

@@ -0,0 +1,34 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+#
+#    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.
+
+import webob
+
+from nova import test
+from nova.api.ec2 import faults
+
+
+class TestFaults(test.TestCase):
+    """Tests covering ec2 Fault class."""
+
+    def test_fault_exception(self):
+        """Ensure the status_int is set correctly on faults"""
+        fault = faults.Fault(webob.exc.HTTPBadRequest(
+                             explanation='test'))
+        self.assertTrue(isinstance(fault.wrapped_exc,
+                         webob.exc.HTTPBadRequest))
+
+    def test_fault_exception_status_int(self):
+        """Ensure the status_int is set correctly on faults"""
+        fault = faults.Fault(webob.exc.HTTPNotFound(explanation='test'))
+        self.assertEquals(fault.wrapped_exc.status_int, 404)