Return 409 error if get_vnc_console is called before VM is created

Fixes bug 1034117

In the xenapi driver, the URL returned for a VNC console will include
information to locate the particular VM on the dom0, however the VM isn't
create until part way through the build process. This leaves a window
where a 404 error could be returned by the os-getVNCConsole action.
Change this to return a 409 meaning it's not ready yet.

Change-Id: Icc3b288d1aae12eb264b2be7fc8f9465d568af74

nova/api/openstack/compute/contrib/consoles.py

@@ -48,6 +48,8 @@ class ConsolesController(wsgi.Controller):
                                                       console_type)
         except exception.InstanceNotFound as e:
             raise webob.exc.HTTPNotFound(explanation=unicode(e))
+        except exception.InstanceNotReady as e:
+            raise webob.exc.HTTPConflict(explanation=unicode(e))
 
         return {'console': {'type': console_type, 'url': output['url']}}
 

nova/exception.py

@@ -327,6 +327,10 @@ class InstanceNotInRescueMode(Invalid):
     message = _("Instance %(instance_id)s is not in rescue mode")
 
 
+class InstanceNotReady(Invalid):
+    message = _("Instance %(instance_id)s is not ready")
+
+
 class InstanceSuspendFailure(Invalid):
     message = _("Failed to suspend instance") + ": %(reason)s"
 

nova/tests/api/openstack/compute/contrib/test_consoles.py

@@ -31,6 +31,10 @@ def fake_get_vnc_console_invalid_type(self, _context,
     raise exception.ConsoleTypeInvalid(console_type=_console_type)
 
 
+def fake_get_vnc_console_not_ready(self, _context, instance, _console_type):
+    raise exception.InstanceNotReady(instance_id=instance["uuid"])
+
+
 def fake_get_vnc_console_not_found(self, _context, instance, _console_type):
     raise exception.InstanceNotFound(instance_id=instance["uuid"])
 
@@ -64,6 +68,19 @@ class ConsolesExtensionTest(test.TestCase):
         self.assertEqual(output,
             {u'console': {u'url': u'http://fake', u'type': u'novnc'}})
 
+    def test_get_vnc_console_not_ready(self):
+        self.stubs.Set(compute.API, 'get_vnc_console',
+                       fake_get_vnc_console_not_ready)
+        body = {'os-getVNCConsole': {'type': 'novnc'}}
+        req = webob.Request.blank('/v2/fake/servers/1/action')
+        req.method = "POST"
+        req.body = jsonutils.dumps(body)
+        req.headers["content-type"] = "application/json"
+
+        res = req.get_response(fakes.wsgi_app())
+        output = jsonutils.loads(res.body)
+        self.assertEqual(res.status_int, 409)
+
     def test_get_vnc_console_no_type(self):
         self.stubs.Set(compute.API, 'get', fake_get)
         self.stubs.Set(compute.API, 'get_vnc_console',

nova/virt/xenapi/vmops.py

@@ -30,6 +30,7 @@ import netaddr
 from nova.compute import api as compute
 from nova.compute import power_state
 from nova.compute import vm_mode
+from nova.compute import vm_states
 from nova import context as nova_context
 from nova import db
 from nova import exception
@@ -1230,7 +1231,21 @@ class VMOps(object):
 
     def get_vnc_console(self, instance):
         """Return connection info for a vnc console."""
-        vm_ref = self._get_vm_opaque_ref(instance)
+        # NOTE(johannes): This can fail if the VM object hasn't been created
+        # yet on the dom0. Since that step happens fairly late in the build
+        # process, there's a potential for a race condition here. Until the
+        # VM object is created, return back a 409 error instead of a 404
+        # error.
+        try:
+            vm_ref = self._get_vm_opaque_ref(instance)
+        except exception.NotFound:
+            if instance['vm_state'] != vm_states.BUILDING:
+                raise
+
+            LOG.info(_('Fetching VM ref while BUILDING failed'),
+                     instance=instance)
+            raise exception.InstanceNotReady(instance_id=instance['uuid'])
+
         session_id = self._session.get_session_id()
         path = "/console?ref=%s&session_id=%s" % (str(vm_ref), session_id)