Purge old packages on upgrade-charm

On charm upgrade the charm may switch to py3 packages. If so, ensure
the old py2 packages are purged. If the purge occurs then restart
services.

Change-Id: I17abef16afbb8c62dae1b725c74c39cec414f4f8
Closes-Bug: 1803451

hooks/nova_compute_hooks.py

@@ -110,6 +110,7 @@ from nova_compute_utils import (
     pause_unit_helper,
     resume_unit_helper,
     get_availability_zone,
+    remove_old_packages,
 )
 
 from charmhelpers.contrib.network.ip import (
@@ -421,9 +422,16 @@ def relation_broken():
 @hooks.hook('upgrade-charm')
 @harden()
 def upgrade_charm():
+    apt_install(determine_packages(), fatal=True)
     # NOTE: ensure psutil install for hugepages configuration
     status_set('maintenance', 'Installing apt packages')
     apt_install(filter_installed_packages(['python-psutil']))
+    packages_removed = remove_old_packages()
+    if packages_removed and not is_unit_paused_set():
+        log("Package purge detected, restarting services", "INFO")
+        for s in services():
+            service_restart(s)
+
     for r_id in relation_ids('amqp'):
         amqp_joined(relation_id=r_id)
 

hooks/nova_compute_utils.py

@@ -435,6 +435,22 @@ def determine_purge_packages():
     return []
 
 
+def remove_old_packages():
+    '''Purge any packages that need ot be removed.
+
+    :returns: bool Whether packages were removed.
+    '''
+    installed_packages = filter_missing_packages(
+        determine_purge_packages()
+    )
+    if installed_packages:
+        apt_mark(filter_missing_packages(determine_held_packages()),
+                 'auto')
+        apt_purge(installed_packages, fatal=True)
+        apt_autoremove(purge=True, fatal=True)
+    return bool(installed_packages)
+
+
 def determine_held_packages():
     '''Return a list of packages to mark as candidates for removal
     for the current OS release'''
@@ -616,14 +632,7 @@ def do_openstack_upgrade(configs):
     reset_os_release()
     apt_install(determine_packages(), fatal=True)
 
-    installed_packages = filter_missing_packages(
-        determine_purge_packages()
-    )
-    if installed_packages:
-        apt_mark(filter_missing_packages(determine_held_packages()),
-                 'auto')
-        apt_purge(installed_packages, fatal=True)
-        apt_autoremove(purge=True, fatal=True)
+    remove_old_packages()
 
     configs.set_release(openstack_release=new_os_rel)
     configs.write_all()

unit_tests/test_nova_compute_hooks.py

@@ -95,6 +95,8 @@ TO_PATCH = [
     'unitdata',
     # templating
     'render',
+    'remove_old_packages',
+    'services',
 ]
 
 
@@ -739,3 +741,24 @@ class NovaComputeRelationsTests(CharmTestCase):
     def test_cloud_credentials_changed(self, mock_CONFIGS):
         hooks.cloud_credentials_changed()
         mock_CONFIGS.write.assert_called_with('/etc/nova/nova.conf')
+
+    @patch.object(hooks.grp, 'getgrnam')
+    def test_upgrade_charm(self, getgrnam):
+        grp_mock = MagicMock()
+        grp_mock.gr_gid = None
+        getgrnam.return_value = grp_mock
+        self.remove_old_packages.return_value = False
+        hooks.upgrade_charm()
+        self.remove_old_packages.assert_called_once_with()
+        self.assertFalse(self.service_restart.called)
+
+    @patch.object(hooks.grp, 'getgrnam')
+    def test_upgrade_charm_purge(self, getgrnam):
+        grp_mock = MagicMock()
+        grp_mock.gr_gid = None
+        getgrnam.return_value = grp_mock
+        self.remove_old_packages.return_value = True
+        self.services.return_value = ['nova-compute']
+        hooks.upgrade_charm()
+        self.remove_old_packages.assert_called_once_with()
+        self.service_restart.assert_called_once_with('nova-compute')