Generate request id and return in header to client

* Generate a uuid in RequestContext.request_id on init
* Present request_id in an 'x-openstack-request-id' header using
  process_response in the ContextMiddlewares
* Related to bp glance-request-tracking

Change-Id: Idd9b86661322250b6167a1ee23e5baae91066ff6

glance/api/middleware/context.py

@@ -15,6 +15,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import logging
 import webob.exc
 
 from glance.common import wsgi
@@ -31,12 +32,21 @@ context_opts = [
 CONF = cfg.CONF
 CONF.register_opts(context_opts)
 
+LOG = logging.getLogger(__name__)
 
-class ContextMiddleware(wsgi.Middleware):
 
-    def __init__(self, app):
-        super(ContextMiddleware, self).__init__(app)
+class BaseContextMiddleware(wsgi.Middleware):
+    def process_response(self, resp):
+        try:
+            request_id = resp.request.context.request_id
+        except AttributeError:
+            LOG.error(_('Unable to retrieve request id from context'))
+        else:
+            resp.headers['x-openstack-request-id'] = 'req-%s' % request_id
+        return resp
 
+
+class ContextMiddleware(BaseContextMiddleware):
     def process_request(self, req):
         """Convert authentication information into a request context
 
@@ -87,11 +97,7 @@ class ContextMiddleware(wsgi.Middleware):
         return glance.context.RequestContext(**kwargs)
 
 
-class UnauthenticatedContextMiddleware(wsgi.Middleware):
-
-    def __init__(self, app):
-        super(UnauthenticatedContextMiddleware, self).__init__(app)
-
+class UnauthenticatedContextMiddleware(BaseContextMiddleware):
     def process_request(self, req):
         """Create a context without an authorized user."""
         kwargs = {

glance/context.py

@@ -15,6 +15,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import glance.common.utils
+
 
 class RequestContext(object):
     """
@@ -33,6 +35,7 @@ class RequestContext(object):
         self.read_only = read_only
         self._show_deleted = show_deleted
         self.owner_is_tenant = owner_is_tenant
+        self.request_id = glance.common.utils.generate_uuid()
 
     @property
     def owner(self):

glance/tests/unit/test_context.py

@@ -233,3 +233,8 @@ class TestContext(utils.BaseTestCase):
         """
         self.do_sharable(True, 'pattieblack', _fake_membership(True),
                          tenant='froggy')
+
+    def test_request_id(self):
+        contexts = [context.RequestContext().request_id for _ in range(5)]
+        # Check for uniqueness -- set() will normalize its argument
+        self.assertEqual(5, len(set(contexts)))

glance/tests/unit/test_context_middleware.py

@@ -2,6 +2,7 @@
 import webob
 
 from glance.api.middleware import context
+import glance.context
 from glance.tests.unit import base
 
 
@@ -99,3 +100,13 @@ class TestUnauthenticatedContextMiddleware(base.IsolatedUnitTest):
         self.assertEqual(req.context.tenant, None)
         self.assertEqual(req.context.roles, [])
         self.assertTrue(req.context.is_admin)
+
+    def test_response(self):
+        middleware = context.UnauthenticatedContextMiddleware(None)
+        req = webob.Request.blank('/')
+        req.context = glance.context.RequestContext()
+        resp = webob.Response()
+        resp.request = req
+        middleware.process_response(resp)
+        self.assertEqual(resp.headers['x-openstack-request-id'],
+                         'req-%s' % req.context.request_id)