software/kvm: Recover from empty backup

software/kvm/buildout.hash.cfg

@@ -43,7 +43,7 @@ md5sum = a02f0694dcb944c18d99f7f79afa2384
 
 [template-kvm-export-script]
 filename = template/kvm-export.sh.jinja2
-md5sum = 3540b42e0869b409846a1601b6ea4dcc
+md5sum = ba1e0359178925788792a1c6cc29ba59
 
 [template-nginx]
 filename = template/nginx_conf.in

software/kvm/template/kvm-export.sh.jinja2

@@ -28,6 +28,9 @@ if [ $RESULT -ne 0 ] ; then
     find $BACKUP_DIR/{{ disk['device'] }} -name '*.qcow2' -delete
     $qmpbackup --level full || exit $?
     echo "Post take-over cleanup"
+  elif egrep -q 'No full backup found for device.*{{ disk['device']}}.*in.*{{ disk['device']}}.*: Execute full backup first.' $log ; then
+    $qmpbackup --level full || exit $?
+    echo "Recovered from empty backup"
   else
     exit $RESULT
   fi

software/kvm/test/test.py

@@ -966,6 +966,10 @@ class TestInstanceResilientBackupExporter(
       'Recovered from partial backup by removing partial',
       status_text
     )
+    self.assertNotIn(
+      'Recovered from empty backup',
+      status_text
+    )
     # cover .partial file in the backup directory with fallback to full
     current_backup = glob.glob(self.getBackupPartitionPath('FULL-*'))[0]
     with open(current_backup + '.partial', 'w') as fh:
@@ -984,6 +988,25 @@ class TestInstanceResilientBackupExporter(
     self.assertTrue(os.path.exists(os.path.join(
       self.getPartitionPath(
         'kvm-export', 'etc', 'plugin', 'check-backup-directory.py'))))
+    # cover empty backup recovery
+    current_backup_list = glob.glob(self.getBackupPartitionPath('*.qcow2'))
+    self.assertEqual(
+      1,
+      len(current_backup_list)
+    )
+    for file in current_backup_list:
+      os.unlink(file)
+    status_text = self.call_exporter()
+    self.assertEqual(
+      len(glob.glob(self.getBackupPartitionPath('FULL-*.qcow2'))),
+      1)
+    self.assertEqual(
+      len(glob.glob(self.getBackupPartitionPath('INC-*.qcow2'))),
+      0)
+    self.assertIn(
+      'Recovered from empty backup',
+      status_text
+    )
 
 
 @skipUnlessKvm