Handle "no RAM info was set" migration case

This handles the case where the live migration monitoring thread may
race and call jobStats() after the migration has completed resulting in
the following error:

    libvirt.libvirtError: internal error: migration was active, but no
    RAM info was set

Closes-Bug: #1982284
Change-Id: I77fdfa9cffbd44b2889f49f266b2582bcc6a4267
(cherry picked from commit 9fea934c71d3c2fa7fdd80c67d94e18466c5cf9a)

3 files changed, 40 insertions, 0 deletions

diff --git a/nova/tests/unit/virt/libvirt/test_guest.py b/nova/tests/unit/virt/libvirt/test_guest.py
index 47ee228943..5b181b8f06 100644
--- a/nova/tests/unit/virt/libvirt/test_guest.py
+++ b/nova/tests/unit/virt/libvirt/test_guest.py
@@ -1053,3 +1053,25 @@ class JobInfoTestCase(test.NoDBTestCase):
 
         mock_stats.assert_called_once_with()
         mock_info.assert_called_once_with()
+
+    @mock.patch.object(fakelibvirt.virDomain, "jobInfo")
+    @mock.patch.object(fakelibvirt.virDomain, "jobStats")
+    def test_job_stats_no_ram(self, mock_stats, mock_info):
+        mock_stats.side_effect = fakelibvirt.make_libvirtError(
+            fakelibvirt.libvirtError,
+            "internal error: migration was active, but no RAM info was set",
+            error_code=fakelibvirt.VIR_ERR_INTERNAL_ERROR,
+            error_message="migration was active, but no RAM info was set")
+
+        info = self.guest.get_job_info()
+
+        self.assertIsInstance(info, libvirt_guest.JobInfo)
+        self.assertEqual(fakelibvirt.VIR_DOMAIN_JOB_NONE, info.type)
+        self.assertEqual(0, info.time_elapsed)
+        self.assertEqual(0, info.time_remaining)
+        self.assertEqual(0, info.memory_total)
+        self.assertEqual(0, info.memory_processed)
+        self.assertEqual(0, info.memory_remaining)
+
+        mock_stats.assert_called_once_with()
+        self.assertFalse(mock_info.called)
diff --git a/nova/virt/libvirt/guest.py b/nova/virt/libvirt/guest.py
index 4c6fd160a8..c40c3c4a7f 100644
--- a/nova/virt/libvirt/guest.py
+++ b/nova/virt/libvirt/guest.py
@@ -674,6 +674,7 @@ class Guest(object):
                 stats = self._domain.jobStats()
                 return JobInfo(**stats)
             except libvirt.libvirtError as ex:
+                errmsg = ex.get_error_message()
                 if ex.get_error_code() == libvirt.VIR_ERR_NO_SUPPORT:
                     # Remote libvirt doesn't support new API
                     LOG.debug("Missing remote virDomainGetJobStats: %s", ex)
@@ -686,6 +687,12 @@ class Guest(object):
                     # away completclsely
                     LOG.debug("Domain has shutdown/gone away: %s", ex)
                     return JobInfo(type=libvirt.VIR_DOMAIN_JOB_COMPLETED)
+                elif (ex.get_error_code() == libvirt.VIR_ERR_INTERNAL_ERROR and
+                      errmsg and "migration was active, "
+                      "but no RAM info was set" in errmsg):
+                    LOG.debug("Migration is active or completed but "
+                              "virDomainGetJobStats is missing ram: %s", ex)
+                    return JobInfo(type=libvirt.VIR_DOMAIN_JOB_NONE)
                 else:
                     LOG.debug("Failed to get job stats: %s", ex)
                     raise
diff --git a/releasenotes/notes/bug-1982284-libvirt-handle-no-ram-info-was-set-99784934ed80fd72.yaml b/releasenotes/notes/bug-1982284-libvirt-handle-no-ram-info-was-set-99784934ed80fd72.yaml
new file mode 100644
index 0000000000..943aa99a43
--- /dev/null
+++ b/releasenotes/notes/bug-1982284-libvirt-handle-no-ram-info-was-set-99784934ed80fd72.yaml
@@ -0,0 +1,11 @@
+---
+other:
+  - |
+    A workaround has been added to the libvirt driver to catch and pass
+    migrations that were previously failing with the error:
+
+    ``libvirt.libvirtError: internal error: migration was active, but no RAM info was set``
+
+    See `bug 1982284`_ for more details.
+
+    .. _bug 1982284: https://bugs.launchpad.net/nova/+bug/1982284