Improve snap channel refresh mechanism

- stop vault.service before rephrasing it
- added a warning note that changing the channel config option will
  cause the vault to be sealed

Related-Bug: 2007587
Change-Id: I240ebb4bd14932a6bf95f41da3f2cd7776742266
(cherry picked from commit 9e927889d0)

src/config.yaml

@@ -56,6 +56,9 @@ options:
     default: 1.7/stable
     description: >-
       The snap channel to install from.
+      WARNING: Changing this value will cause ALL the vault units to become
+      sealed, due to the snap refresh and the service being restarted on each
+      unit.
   dns-ha-access-record:
     type: string
     default:

src/reactive/vault_handlers.py

@@ -42,8 +42,8 @@ from charmhelpers.core.hookenv import (
 from charmhelpers.core.host import (
     service,
     service_reload,
-    service_restart,
     service_running,
+    service_stop,
     write_file,
     is_container,
 )
@@ -185,12 +185,13 @@ def snap_refresh():
     channel = config('channel') or 'stable'
     if validate_snap_channel(channel):
         clear_flag('snap.channel.invalid')
-        snap.refresh('vault', channel=channel)
+        if snap.get_installed_channel("vault") != channel:
-        if vault.can_restart():
+            log("Stopping the vault.service to perform a snap refresh")
-            log("Restarting vault", level=DEBUG)
+            service_stop("vault")
-            service_restart('vault')
+            snap.refresh("vault", channel=channel)
-            if config('totally-unsecure-auto-unlock'):
+            log("Vault was refreshed to {}".format(channel))
-                vault.prepare_vault()
+            start_vault()
+            log("The vault.service has been started")
     else:
         set_flag('snap.channel.invalid')
 

unit_tests/test_reactive_vault_handlers.py

@@ -57,8 +57,8 @@ class TestHandlers(unit_tests.test_utils.CharmTestCase):
             'log',
             'network_get_primary_address',
             'open_port',
-            'service_restart',
             'service_running',
+            'service_stop',
             'service',
             'set_state',
             'status_set',
@@ -549,31 +549,28 @@ class TestHandlers(unit_tests.test_utils.CharmTestCase):
         self.config.assert_called_with('channel')
         self.set_flag.assert_called_with('snap.channel.invalid')
 
-    @patch.object(handlers.vault, 'can_restart')
+    @mock.patch.object(handlers, "start_vault")
-    def test_snap_refresh_restartable(self, can_restart):
+    def test_snap_refresh_version_not_changed(self, mock_start_vault):
-        conf = {
+        conf = {'channel': '1.8/edge'}
-            'channel': 'edge',
-            'totally-unsecure-auto-unlock': False}
         self.config.side_effect = lambda x: conf[x]
-        can_restart.return_value = True
+        self.snap.get_installed_channel.return_value = "1.8/edge"
         handlers.snap_refresh()
-        self.snap.refresh.assert_called_with('vault', channel='edge')
+        self.config.assert_called_once_with("channel")
-        self.service_restart.assert_called_with('vault')
+        self.clear_flag.assert_called_once_with('snap.channel.invalid')
-        self.clear_flag.assert_called_with('snap.channel.invalid')
+        self.snap.refresh.assert_not_called()
-        config_calls = [
+        mock_start_vault.assert_not_called()
-            mock.call('channel'),
-            mock.call('totally-unsecure-auto-unlock')]
-        self.config.assert_has_calls(config_calls)
 
-    @patch.object(handlers.vault, 'can_restart')
+    @mock.patch.object(handlers, "start_vault")
-    def test_snap_refresh_not_restartable(self, can_restart):
+    def test_snap_refresh_version_changed(self, mock_start_vault):
-        self.config.return_value = 'edge'
+        conf = {'channel': '1.8/edge'}
-        can_restart.return_value = False
+        self.config.side_effect = lambda x: conf[x]
+        self.snap.get_installed_channel.return_value = "1.8/stable"
         handlers.snap_refresh()
-        self.snap.refresh.assert_called_with('vault', channel='edge')
+        self.config.assert_called_with("channel")
-        self.config.assert_called_with('channel')
+        self.clear_flag.assert_called_once_with('snap.channel.invalid')
-        self.service_restart.assert_not_called()
+        self.service_stop.assert_called_once_with("vault")
-        self.clear_flag.assert_called_with('snap.channel.invalid')
+        self.snap.refresh.assert_called_once_with("vault", channel="1.8/edge")
+        mock_start_vault.assert_called_once()
 
     def test_snap_refresh_invalid_channel(self):
         self.config.return_value = 'foorbar'