If rescue fails don't error the instance

If a rescue attempt fails, the VM's state should return to what it was
before the rescue attempt started, and the user should be notified of
the failure.

Fixes bug: 1170328

Change-Id: If5e97d06a3617adad83a4bba2ac6320616bbe83b

2 files changed, 35 insertions, 2 deletions

diff --git a/nova/compute/manager.py b/nova/compute/manager.py
index 5da050f60..f1ab1629e 100755
--- a/nova/compute/manager.py
+++ b/nova/compute/manager.py
@@ -2007,7 +2007,6 @@ class ComputeManager(manager.SchedulerDependentManager):
     @exception.wrap_exception(notifier=notifier, publisher_id=publisher_id())
     @reverts_task_state
     @wrap_instance_event
-    @wrap_instance_fault
     def rescue_instance(self, context, instance, rescue_password=None):
         """
         Rescue an instance on this host.
@@ -2028,10 +2027,16 @@ class ComputeManager(manager.SchedulerDependentManager):
         else:
             rescue_image_meta = {}
 
-        with self._error_out_instance_on_exception(context, instance['uuid']):
+        try:
             self.driver.rescue(context, instance,
                                self._legacy_nw_info(network_info),
                                rescue_image_meta, admin_password)
+        except Exception as e:
+            LOG.exception(_("Error trying to Rescue Instance"),
+                          instance=instance)
+            raise exception.InstanceNotRescuable(
+                instance_id=instance['uuid'],
+                reason=_("Driver Error: %s") % unicode(e))
 
         current_power_state = self._get_power_state(context, instance)
         self._instance_update(context,
diff --git a/nova/tests/compute/test_compute.py b/nova/tests/compute/test_compute.py
index 6bf612eee..e3db2cdba 100644
--- a/nova/tests/compute/test_compute.py
+++ b/nova/tests/compute/test_compute.py
@@ -22,6 +22,7 @@ import base64
 import copy
 import datetime
 import sys
+import testtools
 import time
 import traceback
 import uuid
@@ -1265,6 +1266,33 @@ class ComputeTestCase(BaseTestCase):
 
         self.compute.terminate_instance(self.context, instance=instance)
 
+    def test_rescue_handle_err(self):
+        # If the driver fails to rescue, instance state should remain the same
+        # and the exception should be converted to InstanceNotRescuable
+        instance = jsonutils.to_primitive(self._create_fake_instance())
+        self.mox.StubOutWithMock(self.compute, '_get_rescue_image_ref')
+        self.mox.StubOutWithMock(nova.virt.fake.FakeDriver, 'rescue')
+
+        self.compute._get_rescue_image_ref(
+            mox.IgnoreArg(), instance).AndReturn('resc_image_ref')
+        nova.virt.fake.FakeDriver.rescue(
+            mox.IgnoreArg(), instance, [], mox.IgnoreArg(), 'password'
+            ).AndRaise(RuntimeError("Try again later"))
+
+        self.mox.ReplayAll()
+
+        expected_message = ('Instance %s cannot be rescued: '
+                            'Driver Error: Try again later' % instance['uuid'])
+        instance['vm_state'] = 'some_random_state'
+
+        with testtools.ExpectedException(
+            exception.InstanceNotRescuable, expected_message):
+                self.compute.rescue_instance(
+                    self.context, instance=instance,
+                    rescue_password='password')
+
+        self.assertEqual('some_random_state', instance['vm_state'])
+
     def test_power_on(self):
         # Ensure instance can be powered on.