From 980d0fcd75c2b15ccb0af857a9848031919c6c7d Mon Sep 17 00:00:00 2001
From: Sean Dague <sean@dague.net>
Date: Thu, 6 Apr 2017 16:00:42 -0400
Subject: [PATCH] Change livesnapshot to true by default

Because of past qemu bugs we set this to default off and required a
workaround to enable it. However these issues appear to be fixed, and
we should enable this by default for people (with the ability to turn
it off if it's causing crashes in their environment). Metacloud/Cisco
has been running default this way the entire time without issue.

Change-Id: I4545cc99683d311c41c8d6d8dc9787ea6ec6cbc9
---
 nova/conf/workarounds.py                          |  2 +-
 .../tests/unit/virt/libvirt/fake_libvirt_utils.py |  2 +-
 nova/tests/unit/virt/libvirt/test_driver.py       | 15 +++++++++++++++
 ...live_snapshot_by_default-f231485fc2bf77f1.yaml | 10 ++++++++++
 4 files changed, 27 insertions(+), 2 deletions(-)
 create mode 100644 releasenotes/notes/live_snapshot_by_default-f231485fc2bf77f1.yaml

diff --git a/nova/conf/workarounds.py b/nova/conf/workarounds.py
index e819a8cd2da6..a53247759019 100644
--- a/nova/conf/workarounds.py
+++ b/nova/conf/workarounds.py
@@ -66,7 +66,7 @@ Interdependencies to other options:
 
     cfg.BoolOpt(
         'disable_libvirt_livesnapshot',
-        default=True,
+        default=False,
         help="""
 Disable live snapshots when using the libvirt driver.
 
diff --git a/nova/tests/unit/virt/libvirt/fake_libvirt_utils.py b/nova/tests/unit/virt/libvirt/fake_libvirt_utils.py
index 0b56cbdc71c6..e6de57c4f4c5 100644
--- a/nova/tests/unit/virt/libvirt/fake_libvirt_utils.py
+++ b/nova/tests/unit/virt/libvirt/fake_libvirt_utils.py
@@ -30,7 +30,7 @@ def create_image(disk_format, path, size):
     pass
 
 
-def create_cow_image(backing_file, path):
+def create_cow_image(backing_file, path, size=None):
     pass
 
 
diff --git a/nova/tests/unit/virt/libvirt/test_driver.py b/nova/tests/unit/virt/libvirt/test_driver.py
index fe54dc75e7f9..8e63fd5d8791 100644
--- a/nova/tests/unit/virt/libvirt/test_driver.py
+++ b/nova/tests/unit/virt/libvirt/test_driver.py
@@ -454,6 +454,7 @@ class FakeVirtDomain(object):
         else:
             self._fake_dom_xml = """
                 <domain type='kvm'>
+                    <name>testinstance1</name>
                     <devices>
                         <disk type='file'>
                             <source file='filename'/>
@@ -510,6 +511,9 @@ class FakeVirtDomain(object):
     def blockJobInfo(self, path, flags):
         pass
 
+    def blockJobAbort(self, path, flags):
+        pass
+
     def resume(self):
         pass
 
@@ -528,6 +532,9 @@ class FakeVirtDomain(object):
     def isPersistent(self):
         return True
 
+    def undefine(self):
+        return True
+
 
 class CacheConcurrencyTestCase(test.NoDBTestCase):
     def setUp(self):
@@ -18998,6 +19005,14 @@ class _BaseSnapshotTests(test.NoDBTestCase):
 
 
 class LibvirtSnapshotTests(_BaseSnapshotTests):
+
+    def setUp(self):
+        super(LibvirtSnapshotTests, self).setUp()
+        # All paths through livesnapshot trigger a chown behind privsep
+        self.privsep_chown = mock.patch.object(nova.privsep.path, 'chown')
+        self.addCleanup(self.privsep_chown.stop)
+        self.privsep_chown.start()
+
     def test_ami(self):
         # Assign different image_ref from nova/images/fakes for testing ami
         self.instance_ref.image_ref = 'c905cedb-7281-47e4-8a62-f26bc5fc4c77'
diff --git a/releasenotes/notes/live_snapshot_by_default-f231485fc2bf77f1.yaml b/releasenotes/notes/live_snapshot_by_default-f231485fc2bf77f1.yaml
new file mode 100644
index 000000000000..4dd334426082
--- /dev/null
+++ b/releasenotes/notes/live_snapshot_by_default-f231485fc2bf77f1.yaml
@@ -0,0 +1,10 @@
+---
+upgrade:
+  - |
+    Nova now defaults to using the live snapshot feature of libvirt
+    when taking snapshots. This was previously disabled by default due
+    to crashes on load seen with older libvirt versions. It has been
+    used in production by many clouds, and appears stable in real
+    world environments. If you see crashes of guests during snapshots,
+    you can disable this with the ``disable_libvirt_livesnapshot``
+    config value in ``[workarounds]``.