Fake missing local_gb for root_device_hint plugin

At the first run of discovery, the RAID volumes might be missing from
the node. To avoid the standard plugin erroring, root_device_hint plugin
fakes the missing local_gb value. The fake value will be overwritten
with the correct one during later runs.

Change-Id: I2d38557fa356656e44e9915d3c4a5abb9cf1731d

ironic_inspector/plugins/root_device_hint.py

@@ -37,8 +37,20 @@ class RootDeviceHintHook(base.ProcessingHook):
     information about the created RAID disks. Using this plugin immediately
     before and after creating the root RAID device will solve the issue of root
     device hints.
+
+    In cases where there's no RAID volume on the node, the standard plugin will
+    fail due to the missing local_gb value. This plugin fakes the missing
+    value, until it's corrected during later runs. Note, that for this to work
+    the plugin needs to take precedence over the standard plugin.
     """
 
+    def before_processing(self, node_info):
+        """Adds fake local_gb value if it's missing from node_info."""
+        if not node_info.get('local_gb'):
+            LOG.info(_LI('No volume is found on the node. Adding a fake '
+                         'value for "local_gb"'))
+            node_info['local_gb'] = 1
+
     def before_update(self, node, ports, node_info):
         if 'block_devices' not in node_info:
             LOG.warning(_LW('No block device was received from ramdisk'))

ironic_inspector/test/test_plugins_root_device_hint.py

@@ -21,6 +21,18 @@ class TestRootDeviceHint(test_base.NodeTest):
         super(TestRootDeviceHint, self).setUp()
         self.hook = root_device_hint.RootDeviceHintHook()
 
+    def test_missing_local_gb(self):
+        node_info = {}
+        self.hook.before_processing(node_info)
+
+        self.assertEqual(1, node_info['local_gb'])
+
+    def test_local_gb_not_changes(self):
+        node_info = {'local_gb': 42}
+        self.hook.before_processing(node_info)
+
+        self.assertEqual(42, node_info['local_gb'])
+
     def test_no_previous_block_devices(self):
         node_info = {'block_devices': {'serials': ['foo', 'bar']}}
         node_patches, _ = self.hook.before_update(self.node, None, node_info)