conf: Deprecate 'disable_libvirt_livesnapshot' option

This was added to handle gate issues seen with libvirt 1.2.2. We haven't
supported that version of libvirt for some time and we don't enable this
in the gate anymore. Deprecate it and remove unnecessary references to
it from tests and the support FAQ document.

Change-Id: Ie3fa537a42d208a35467f03bd2110c2976927477

doc/source/admin/support-compute.rst

@@ -272,30 +272,6 @@ To disable injection in libvirt, set the following in ``nova.conf``:
    injection.
 
 
-Disable live snapshotting
--------------------------
-
-Problem
-~~~~~~~
-
-Administrators using libvirt version ``1.2.2`` may experience problems with
-live snapshot creation. Occasionally, libvirt version ``1.2.2`` fails to create
-live snapshots under the load of creating concurrent snapshot.
-
-Solution
-~~~~~~~~
-
-To effectively disable the libvirt live snapshotting, until the problem is
-resolved, configure the ``disable_libvirt_livesnapshot`` option.  You can turn
-off the live snapshotting mechanism by setting up its value to ``True`` in the
-``[workarounds]`` section of the ``nova.conf`` file:
-
-.. code-block:: ini
-
-   [workarounds]
-   disable_libvirt_livesnapshot = True
-
-
 Cannot find suitable emulator for x86_64
 ----------------------------------------
 

nova/conf/workarounds.py

@@ -67,6 +67,13 @@ Interdependencies to other options:
     cfg.BoolOpt(
         'disable_libvirt_livesnapshot',
         default=False,
+        deprecated_for_removal=True,
+        deprecated_since='19.0.0',
+        deprecated_reason="""
+This option was added to work around issues with libvirt 1.2.2. We no longer
+support this version of libvirt, which means this workaround is no longer
+necessary. It will be removed in a future release.
+""",
         help="""
 Disable live snapshots when using the libvirt driver.
 

nova/tests/unit/virt/libvirt/test_driver.py

@@ -22236,7 +22236,6 @@ class LibvirtSnapshotTests(_BaseSnapshotTests):
     @mock.patch.object(host.Host, 'get_guest')
     @mock.patch.object(host.Host, 'write_instance_config')
     def test_failing_domain_not_found(self, mock_write_config, mock_get_guest):
-        self.flags(disable_libvirt_livesnapshot=False, group='workarounds')
         mock_dev = mock.Mock(spec=libvirt_guest.BlockDevice)
         mock_guest = mock.Mock(spec=libvirt_guest.Guest)
         mock_guest.get_power_state.return_value = power_state.RUNNING
@@ -22338,7 +22337,6 @@ class LibvirtSnapshotTests(_BaseSnapshotTests):
                                                  mock_version,
                                                  mock_resolve,
                                                  mock_snapshot):
-        self.flags(disable_libvirt_livesnapshot=False, group='workarounds')
         self.flags(images_type='rbd', group='libvirt')
         mock_guest = mock.Mock(spec=libvirt_guest.Guest)
         mock_guest._domain = mock.Mock()
@@ -22366,7 +22364,6 @@ class LibvirtSnapshotTests(_BaseSnapshotTests):
                                                            mock_resolve,
                                                            mock_find_disk,
                                                            mock_convert):
-        self.flags(disable_libvirt_livesnapshot=False, group='workarounds')
         self.flags(images_type='rbd', group='libvirt')
         rbd = mock_driver.return_value
         rbd.parent_info = mock.Mock(side_effect=exception.ImageUnacceptable(

releasenotes/notes/deprecate-disable_libvirt_livesnapshot-413c71b96f5e38d4.yaml

@@ -0,0 +1,9 @@
+---
+deprecations:
+  - |
+    The ``[workarounds] disable_libvirt_livesnapshot`` config option has been
+    deprecated. This was necessary to work around an issue with libvirt v1.2.2,
+    which we no longer support. For more information refer to `bug
+    #1334398`__.
+
+    __ https://bugs.launchpad.net/nova/+bug/1334398