Fix get_vnc_console race.

There exists a window between a server create is done and when the host
is assigned by the scheduler that a request to get the vnc console will
result in a 500 error.

This patch adds a check in the compute API to ensure that the instance
has a host assigned before try to execute a rpc on the compute node.
If not, it raises InstanceNotReady (which translates to a 409 in the
OS API).

Fix bug 1037809.

Change-Id: I3f5af90d57ae84f98f787e14ccb66f1841ac0c6d

2 files changed, 12 insertions, 0 deletions

diff --git a/nova/compute/api.py b/nova/compute/api.py
index e7f9368ea..ebf67729d 100644
--- a/nova/compute/api.py
+++ b/nova/compute/api.py
@@ -1627,6 +1627,9 @@ class API(base.Base):
     @wrap_check_policy
     def get_vnc_console(self, context, instance, console_type):
         """Get a url to an instance Console."""
+        if not instance['host']:
+            raise exception.InstanceNotReady(instance=instance)
+
         connect_info = self.compute_rpcapi.get_vnc_console(context,
                 instance=instance, console_type=console_type)
 
diff --git a/nova/tests/compute/test_compute.py b/nova/tests/compute/test_compute.py
index 8a46d51ec..64d7fb960 100644
--- a/nova/tests/compute/test_compute.py
+++ b/nova/tests/compute/test_compute.py
@@ -3896,6 +3896,15 @@ class ComputeAPITestCase(BaseTestCase):
                 fake_instance, fake_console_type)
         self.assertEqual(console, {'url': 'fake_console_url'})
 
+    def test_get_vnc_console_no_host(self):
+        instance = self._create_fake_instance(params={'host': ''})
+
+        self.assertRaises(exception.InstanceNotReady,
+                          self.compute_api.get_vnc_console,
+                          self.context, instance, 'novnc')
+
+        db.instance_destroy(self.context, instance['uuid'])
+
     def test_console_output(self):
         fake_instance = {'uuid': 'fake_uuid',
                          'host': 'fake_compute_host'}