Snapshots/backups can no longer happen simultaneously. Tests included.

Implemented exception.InstanceBusy when attempting to snapshot/backup an
instance which is already snapshotting or being currently backed up.

Fixes bug 727502.

(Patch Set 2) 3 new exceptions: InstanceBusy, InstanceSnapshotting, and InstanceBackingUp
(Patch Set 3) Oops. New exceptions now inherit from InstanceBusy
(Patch Set 4) Tests now tear down created instances

Change-Id: I9614740bba26c04e64b0e27c24fbace12334f4d1

nova/tests/test_compute.py

@@ -36,6 +36,7 @@ from nova import utils
 from nova.compute import instance_types
 from nova.compute import manager as compute_manager
 from nova.compute import power_state
+from nova.compute import task_states
 from nova.compute import vm_states
 from nova.db.sqlalchemy import models
 from nova.image import fake as fake_image
@@ -401,6 +402,36 @@ class ComputeTestCase(test.TestCase):
         self.compute.snapshot_instance(self.context, instance_id, name)
         self.compute.terminate_instance(self.context, instance_id)
 
+    def test_snapshot_conflict_backup(self):
+        """Can't backup an instance which is already being backed up."""
+        instance_id = self._create_instance()
+        instance_values = {'task_state': task_states.IMAGE_BACKUP}
+        db.instance_update(self.context, instance_id, instance_values)
+
+        self.assertRaises(exception.InstanceBackingUp,
+                          self.compute_api.backup,
+                          self.context,
+                          instance_id,
+                          None,
+                          None,
+                          None)
+
+        db.instance_destroy(self.context, instance_id)
+
+    def test_snapshot_conflict_snapshot(self):
+        """Can't snapshot an instance which is already being snapshotted."""
+        instance_id = self._create_instance()
+        instance_values = {'task_state': task_states.IMAGE_SNAPSHOT}
+        db.instance_update(self.context, instance_id, instance_values)
+
+        self.assertRaises(exception.InstanceSnapshotting,
+                          self.compute_api.snapshot,
+                          self.context,
+                          instance_id,
+                          None)
+
+        db.instance_destroy(self.context, instance_id)
+
     def test_console_output(self):
         """Make sure we can get console output from instance"""
         instance_id = self._create_instance()