In placement API send microversion header when error

If there is an exception in the placement API application we still
need to send the openstack-api-version header in the response:
errors are versioned too. Therefore catch the exception, add to its
headers and then reraise the exception.

This was a problem identified in the review of the initial framing
of the placement API but left for a later patch. This is that later
patch.

Change-Id: Ib83acbf74907fd9dcbdd4b0a9271ad4bae1c21b1
Partially-Implements: blueprint generic-resource-pools

nova/api/openstack/placement/microversion.py

@@ -72,8 +72,7 @@ class MicroversionMiddleware(object):
     @webob.dec.wsgify
     def __call__(self, req):
         try:
-            req.environ[MICROVERSION_ENVIRON] = extract_version(
-                req.headers)
+            microversion = extract_version(req.headers)
         except ValueError as exc:
             raise webob.exc.HTTPNotAcceptable(
                 'Invalid microversion: %s' % exc,
@@ -82,10 +81,20 @@ class MicroversionMiddleware(object):
             raise webob.exc.HTTPBadRequest(
                 'Invalid microversion: %s' % exc,
                 json_formatter=util.json_error_formatter)
-        response = req.get_response(self.application)
-        response.headers.add(Version.HEADER,
-                             '%s %s' % (SERVICE_TYPE,
-                                        req.environ[MICROVERSION_ENVIRON]))
+
+        req.environ[MICROVERSION_ENVIRON] = microversion
+        microversion_header = '%s %s' % (SERVICE_TYPE, microversion)
+
+        try:
+            response = req.get_response(self.application)
+        except webob.exc.HTTPError as exc:
+            # If there was an error in the application we still need
+            # to send the microversion header, so add the header and
+            # re-raise the exception.
+            exc.headers.add(Version.HEADER, microversion_header)
+            raise exc
+
+        response.headers.add(Version.HEADER, microversion_header)
         response.headers.add('vary', Version.HEADER)
         return response
 

nova/tests/functional/api/openstack/placement/gabbits/microversion.yaml

@@ -71,3 +71,9 @@ tests:
   status: 400
   response_strings:
       - "invalid version string: 1.2.3"
+
+- name: error in application produces microversion headers
+  POST: /
+  status: 405
+  response_headers:
+      openstack-api-version: placement 1.0