RBD: support to report backend state

This patch adds the ability to report backend state to RBD driver.

Partial-Implements: blueprint report-backend-state-in-service-list

Change-Id: Ib703786d77621ec139e4f3981506ed117b737524

cinder/tests/unit/volume/drivers/test_rbd.py

@@ -1201,7 +1201,8 @@ class RBDTestCase(test.TestCase):
             provisioned_capacity_gb=mock.sentinel.provisioned_capacity_gb,
             max_over_subscription_ratio=1.0,
             multiattach=False,
-            location_info=expected_location_info)
+            location_info=expected_location_info,
+            backend_state='up')
 
         if replication_enabled:
             targets = [{'backend_id': 'secondary-backend'},
@@ -1244,7 +1245,8 @@ class RBDTestCase(test.TestCase):
             thin_provisioning_support=True,
             max_over_subscription_ratio=1.0,
             multiattach=False,
-            location_info=expected_location_info)
+            location_info=expected_location_info,
+            backend_state='up')
 
         my_safe_get = MockDriverConfig(rbd_exclusive_cinder_pool=True)
         self.mock_object(self.driver.configuration, 'safe_get',
@@ -1280,7 +1282,8 @@ class RBDTestCase(test.TestCase):
                         multiattach=False,
                         max_over_subscription_ratio=1.0,
                         thin_provisioning_support=True,
-                        location_info=expected_location_info)
+                        location_info=expected_location_info,
+                        backend_state='down')
 
         with mock.patch.object(self.driver, '_get_fsid') as mock_get_fsid:
             mock_get_fsid.return_value = expected_fsid

cinder/volume/drivers/rbd.py

@@ -495,6 +495,7 @@ class RBDDriver(driver.CloneableImageVD, driver.MigrateVD,
             'max_over_subscription_ratio': (
                 self.configuration.safe_get('max_over_subscription_ratio')),
             'location_info': location_info,
+            'backend_state': 'down'
         }
 
         backend_name = self.configuration.safe_get('volume_backend_name')
@@ -514,6 +515,8 @@ class RBDDriver(driver.CloneableImageVD, driver.MigrateVD,
             if not self.configuration.safe_get('rbd_exclusive_cinder_pool'):
                 total_gbi = self._get_usage_info()
                 stats['provisioned_capacity_gb'] = total_gbi
+
+            stats['backend_state'] = 'up'
         except self.rados.Error:
             # just log and return unknown capacities and let scheduler set
             # provisioned_capacity_gb = allocated_capacity_gb

releasenotes/notes/rbd-support-report-backend-state-4e124eb9efd36724.yaml

@@ -0,0 +1,3 @@
+---
+features:
+  - Allow rbd driver to report backend state.