Set nova config for rbd instance folder cleanup after evacuations

After evacuations and revert resizes when using rbd storage backend,
the instance folder is usually left behind and causes issues when
migrating the instance back to the host.
With the config option set, the nova-compute service will cleanup
those folders as part of the periodic checks that run for instances
that have been evacuated/migrated.

Closes-bug: #2019141
Change-Id: I846ccb0a95d04139b41fdad6cbf465d303d6cc09
(cherry picked from commit e61d89aa47)
(cherry picked from commit 003f6b6d70)
(cherry picked from commit cfafa8cf5f)
(cherry picked from commit 1ddfe5e6c2)
(cherry picked from commit d3e4cc31c6)
(cherry picked from commit be845826f9)
(cherry picked from commit f1ff0d55b8)

hooks/nova_compute_context.py

@@ -16,6 +16,7 @@ import json
 import os
 import platform
 import shutil
+import subprocess
 import uuid
 
 from charmhelpers.core.unitdata import kv
@@ -38,6 +39,7 @@ from charmhelpers.core.hookenv import (
     service_name,
     ERROR,
     INFO,
+    DEBUG,
 )
 from charmhelpers.contrib.openstack.utils import (
     get_os_version_package,
@@ -95,6 +97,16 @@ def _get_availability_zone():
     return get_az()
 
 
+def is_local_fs(path):
+    result = False
+    try:
+        subprocess.check_call(["df", "-l", path])
+        result = True
+    except subprocess.CalledProcessError as e:
+        log("Error invoking df -l {}: {}".format(path, e), level=DEBUG)
+    return result
+
+
 def _neutron_security_groups():
     '''
     Inspects current cloud-compute relation and determine if nova-c-c has
@@ -314,6 +326,17 @@ class NovaComputeLibvirtContext(context.OSContextGenerator):
 
         if config('libvirt-image-backend'):
             ctxt['libvirt_images_type'] = config('libvirt-image-backend')
+            if config('libvirt-image-backend') == 'rbd':
+                instances_path = config('instances-path')
+                if instances_path in ('', None):
+                    instances_path = '/var/lib/nova/instances'
+                if is_local_fs(instances_path):
+                    ctxt['ensure_libvirt_rbd_instance_dir_cleanup'] = True
+                else:
+                    log("Skipped enabling "
+                        "'ensure_libvirt_rbd_instance_dir_cleanup' because"
+                        " instances-path is not a local mount.",
+                        level=INFO)
 
         ctxt['force_raw_images'] = config('force-raw-images')
         ctxt['inject_password'] = config('inject-password')

templates/train/nova.conf

@@ -360,6 +360,9 @@ lock_path=/var/lock/nova
 
 [workarounds]
 disable_libvirt_livesnapshot = False
+{% if ensure_libvirt_rbd_instance_dir_cleanup -%}
+ensure_libvirt_rbd_instance_dir_cleanup = {{ ensure_libvirt_rbd_instance_dir_cleanup }}
+{% endif -%}
 
 {% include "parts/section-ephemeral" %}
 

unit_tests/test_nova_compute_contexts.py

@@ -384,6 +384,36 @@ class NovaComputeContextTests(CharmTestCase):
              'default_ephemeral_format': 'ext4',
              'reserved_host_memory': 512}, libvirt())
 
+    @patch.object(context.subprocess, 'check_call')
+    def test_ensure_rbd_cleanup_rbd(self, call_mock):
+        self.lsb_release.return_value = {'DISTRIB_CODENAME': 'focal'}
+        self.os_release.return_value = 'ussuri'
+        self.test_config.set('libvirt-image-backend', 'rbd')
+        libvirt = context.NovaComputeLibvirtContext()
+        result = libvirt()
+        self.assertIn('ensure_libvirt_rbd_instance_dir_cleanup', result)
+        self.assertTrue(result['ensure_libvirt_rbd_instance_dir_cleanup'])
+        call_mock.assert_called_once_with(
+            ['df', '-l', '/var/lib/nova/instances'])
+
+    @patch.object(context.subprocess, 'check_call')
+    def test_ensure_rbd_cleanup_rbd_non_local_mount(self, call_mock):
+        self.lsb_release.return_value = {'DISTRIB_CODENAME': 'focal'}
+        self.os_release.return_value = 'ussuri'
+        call_mock.side_effect = [context.subprocess.CalledProcessError(
+            1, 'df -l /var/foo/bar')]
+        self.test_config.set('libvirt-image-backend', 'rbd')
+        self.test_config.set('instances-path', '/var/foo/bar')
+        libvirt = context.NovaComputeLibvirtContext()
+        self.assertNotIn('ensure_libvirt_rbd_instance_dir_cleanup', libvirt())
+        call_mock.assert_called_once_with(['df', '-l', '/var/foo/bar'])
+
+    def test_ensure_rbd_cleanup_non_rbd(self):
+        self.lsb_release.return_value = {'DISTRIB_CODENAME': 'focal'}
+        self.os_release.return_value = 'ussuri'
+        libvirt = context.NovaComputeLibvirtContext()
+        self.assertNotIn('ensure_libvirt_rbd_instance_dir_cleanup', libvirt())
+
     def test_libvirt_context_inject_password(self):
         self.lsb_release.return_value = {'DISTRIB_CODENAME': 'zesty'}
         self.os_release.return_value = 'ocata'