Reply with a meaningful exception, when libvirt connection is broken.

Libvirt driver will respond with a meaningful error on any
command, when the connection to the libvirt service is broken.

Closes-bug: #1240344
Change-Id: I823fefaffcf969ecf9eb853ac99dc18cef92d137

nova/exception.py

@@ -392,6 +392,10 @@ class ComputeResourcesUnavailable(ServiceUnavailable):
     msg_fmt = _("Insufficient compute resources.")
 
 
+class HypervisorUnavailable(NovaException):
+    msg_fmt = _("Connection to the hypervisor is broken on host: %(host)s")
+
+
 class ComputeServiceUnavailable(ServiceUnavailable):
     msg_fmt = _("Compute service of %(host)s is unavailable at this time.")
 

nova/tests/virt/libvirt/test_libvirt.py

@@ -3820,6 +3820,21 @@ def test_broken_connection(self):
 
             self.mox.UnsetStubs()
 
+    def test_command_with_broken_connection(self):
+        self.mox.UnsetStubs()
+        conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), False)
+        self.mox.StubOutWithMock(libvirt, "openAuth")
+        self.mox.StubOutWithMock(libvirt.libvirtError, "get_error_code")
+        self.mox.StubOutWithMock(libvirt.libvirtError, "get_error_domain")
+        libvirt.openAuth(mox.IgnoreArg(), mox.IgnoreArg(),
+                         mox.IgnoreArg()).AndRaise(
+                                     libvirt.libvirtError("fake failure"))
+
+        self.mox.ReplayAll()
+        conn._close_callback(conn._wrapped_conn, 'ERROR', '')
+        self.assertRaises(exception.HypervisorUnavailable,
+                          conn.get_num_instances)
+
     def test_immediate_delete(self):
         def fake_lookup_by_name(instance_name):
             raise exception.InstanceNotFound(instance_id=instance_name)

nova/virt/libvirt/driver.py

@@ -683,6 +683,7 @@ def _connect_auth_cb(creds, opaque):
             notifier.get_notifier('compute').error(
                 nova_context.get_admin_context(),
                 'compute.libvirt.error', payload)
+            raise exception.HypervisorUnavailable(host=CONF.host)
 
     def get_num_instances(self):
         """Efficient override of base instance_exists method."""