Deal with obsolete packages during charm upgrade

For Rocky, we switch the payload execution environent from py2->py3
post initial charm release; ensure that any existing py2 based
deployments are automatically switched over to py3 during any
charm upgrade.

This is implemented in the default upgrade-charm handler code; if
packages are removed as part of the upgrade, all services associated
with the charm will be restarted.

Change-Id: Ib5f11d21dd26cb2918f5d5044ed56d688bba3b5d
Closes-Bug: 1803451

charms_openstack/charm/core.py

@@ -826,8 +826,14 @@ class BaseOpenStackCharmActions(object):
         that the ports that are closed should be closed.  If the charm upgrade
         alters the ports then update_api_ports() function will adjust the ports
         as needed.
+
+        Obsolete packages will also be assessed for removal; if packages are
+        removed, then services will be restarted to pickup any changes.
         """
         self.update_api_ports()
+        self.install()
+        if self.remove_obsolete_packages():
+            self.restart_all()
 
     def update_api_ports(self, ports=None):
         """Update the ports list supplied (or the default ports defined in the
@@ -949,6 +955,14 @@ class BaseOpenStackCharmActions(object):
             packages=self.all_packages,
             options=dpkg_opts,
             fatal=True)
+        self.remove_obsolete_packages()
+        self.release = new_os_rel
+
+    def remove_obsolete_packages(self):
+        """Remove any packages that are no longer needed for operation
+
+        :returns: boolean indication where packages where removed.
+        """
         if self.purge_packages:
             # NOTE(jamespage):
             # Ensure packages that should be purged are actually installed
@@ -960,7 +974,8 @@ class BaseOpenStackCharmActions(object):
                 fetch.apt_purge(packages=installed_packages,
                                 fatal=True)
                 fetch.apt_autoremove(purge=True, fatal=True)
-        self.release = new_os_rel
+                return True
+        return False
 
     def do_openstack_upgrade_config_render(self, interfaces_list):
         """Render configs after upgrade

unit_tests/charms_openstack/charm/test_core.py

@@ -780,6 +780,30 @@ class TestMyOpenStackCharm(BaseOpenStackCharmTest):
         (target_charm.do_openstack_upgrade_db_migration.
             assert_called_once_with())
 
+    def test_remove_obsolete_packages(self):
+        self.patch_object(chm_core.charmhelpers.fetch, 'apt_purge')
+        self.patch_object(chm_core.charmhelpers.fetch, 'apt_autoremove')
+        self.patch_object(chm_core.charmhelpers.fetch,
+                          'filter_installed_packages',
+                          return_value=['python-notinstalled'])
+        self.assertTrue(self.target.remove_obsolete_packages())
+        self.apt_purge.assert_called_once_with(
+            packages=['python-obsolete'],
+            fatal=True)
+        self.apt_autoremove.assert_called_once_with(
+            purge=True,
+            fatal=True)
+
+    def test_remove_obsolete_packages_noop(self):
+        self.patch_object(chm_core.charmhelpers.fetch, 'apt_purge')
+        self.patch_object(chm_core.charmhelpers.fetch, 'apt_autoremove')
+        self.patch_object(chm_core.charmhelpers.fetch,
+                          'filter_installed_packages',
+                          return_value=self.target.purge_packages)
+        self.assertFalse(self.target.remove_obsolete_packages())
+        self.apt_purge.assert_not_called()
+        self.apt_autoremove.assert_not_called()
+
     def test_do_openstack_pkg_upgrade_package(self):
         self.patch_target('config',
                           new={'openstack-origin': 'cloud:natty-kilo'})
@@ -874,3 +898,27 @@ class TestMyOpenStackCharm(BaseOpenStackCharmTest):
         self.is_leader.return_value = True
         self.target.do_openstack_upgrade_db_migration()
         self.check_call.assert_called_once_with(['my-sync-cmd', 'param1'])
+
+    def test_upgrade_charm(self):
+        self.target.update_api_ports = mock.MagicMock()
+        self.target.install = mock.MagicMock()
+        self.target.remove_obsolete_packages = mock.MagicMock()
+        self.target.remove_obsolete_packages.return_value = True
+        self.target.restart_all = mock.MagicMock()
+        self.target.upgrade_charm()
+        self.target.update_api_ports.assert_called_once()
+        self.target.install.assert_called_once()
+        self.target.remove_obsolete_packages.assert_called_once()
+        self.target.restart_all.assert_called_once()
+
+    def test_upgrade_charm_no_purge(self):
+        self.target.update_api_ports = mock.MagicMock()
+        self.target.install = mock.MagicMock()
+        self.target.remove_obsolete_packages = mock.MagicMock()
+        self.target.remove_obsolete_packages.return_value = False
+        self.target.restart_all = mock.MagicMock()
+        self.target.upgrade_charm()
+        self.target.update_api_ports.assert_called_once()
+        self.target.install.assert_called_once()
+        self.target.remove_obsolete_packages.assert_called_once()
+        self.target.restart_all.assert_not_called()