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: Iddfff1c7ce929776c294034706305f5d77ae9ade
Closes-Bug: 1803451

hooks/neutron_hooks.py

@@ -71,6 +71,7 @@ from neutron_utils import (
     resume_unit_helper,
     remove_legacy_nova_metadata,
     disable_nova_metadata,
+    remove_old_packages,
 )
 
 hooks = Hooks()
@@ -160,6 +161,11 @@ def config_changed():
 @harden()
 def upgrade_charm():
     install()
+    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)
     config_changed()
     update_legacy_ha_files(force=True)
 

hooks/neutron_utils.py

@@ -293,6 +293,18 @@ def get_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(get_purge_packages())
+    if installed_packages:
+        apt_purge(installed_packages, fatal=True)
+        apt_autoremove(purge=True, fatal=True)
+    return bool(installed_packages)
+
+
 def determine_l3ha_packages():
     if use_l3ha():
         return L3HA_PACKAGES
@@ -754,10 +766,8 @@ def do_openstack_upgrade(configs):
     apt_install(get_early_packages(), fatal=True)
     apt_install(get_packages(), fatal=True)
 
-    installed_packages = filter_missing_packages(get_purge_packages())
-    if installed_packages:
-        apt_purge(installed_packages, fatal=True)
-        apt_autoremove(purge=True, fatal=True)
+    remove_old_packages()
+
     # Bug #1802365 neutron-metadata-agent needs restarting after upgrade to
     # rocky.
     if CompareOpenStackReleases(os_release('neutron-common')) == 'rocky':

unit_tests/test_neutron_hooks.py

@@ -61,6 +61,8 @@ TO_PATCH = [
     'configure_apparmor',
     'disable_nova_metadata',
     'remove_legacy_nova_metadata',
+    'services',
+    'remove_old_packages',
 ]
 
 
@@ -160,6 +162,7 @@ class TestQuantumHooks(CharmTestCase):
         _exit.assert_called_with(1)
 
     def test_upgrade_charm(self):
+        self.remove_old_packages.return_value = False
         _install = self.patch('install')
         _config_changed = self.patch('config_changed')
         self._call_hook('upgrade-charm')
@@ -167,6 +170,18 @@ class TestQuantumHooks(CharmTestCase):
         self.assertTrue(_config_changed.called)
         self.assertTrue(self.install_systemd_override.called)
 
+    def test_upgrade_charm_purge(self):
+        self.is_unit_paused_set.return_value = False
+        self.remove_old_packages.return_value = True
+        self.services.return_value = ['neutron-metadata-agent']
+        _install = self.patch('install')
+        _config_changed = self.patch('config_changed')
+        self._call_hook('upgrade-charm')
+        self.assertTrue(_install.called)
+        self.assertTrue(_config_changed.called)
+        self.assertTrue(self.install_systemd_override.called)
+        self.service_restart.assert_called_once_with('neutron-metadata-agent')
+
     def test_amqp_joined(self):
         self._call_hook('amqp-relation-joined')
         self.relation_set.assert_called_with(