avoid restart being triggered after upgrade (#451)

Author: paulomach

src/charm.py

@@ -240,11 +240,8 @@ def _on_config_changed(self, event: EventBase) -> None:
             # the upgrade already restart the daemon
             return
 
-        if not self._mysql.is_mysqld_running():
-            # defer config-changed event until MySQL is running
-            logger.debug("Deferring config-changed event until MySQL is running")
-            event.defer()
-            return
+        # restart not required if mysqld is not running
+        restart = self._mysql.is_mysqld_running()
 
         previous_config = self.mysql_config.custom_config
         if not previous_config:
@@ -263,14 +260,15 @@ def _on_config_changed(self, event: EventBase) -> None:
 
         if self.mysql_config.keys_requires_restart(changed_config):
             # there are static configurations in changed keys
-            logger.info("Configuration change requires restart")
-
+            logger.info("Persisting configuration changes to file")
             # persist config to file
             self._mysql.write_content_to_file(
                 path=MYSQLD_CUSTOM_CONFIG_FILE, content=new_config_content
             )
-            self.on[f"{self.restart.name}"].acquire_lock.emit()
-            return
+            if restart:
+                logger.info("Configuration change requires restart")
+                self.on[f"{self.restart.name}"].acquire_lock.emit()
+                return
 
         if dynamic_config := self.mysql_config.filter_static_keys(changed_config):
             # if only dynamic config changed, apply it
@@ -796,6 +794,11 @@ def join_unit_to_cluster(self) -> None:
 
     def _restart(self, event: EventBase) -> None:
         """Restart the MySQL service."""
+        if self.peers.units != self.restart_peers.units:
+            # defer restart until all units are in the relation
+            logger.debug("Deferring restart until all units are in the relation")
+            event.defer()
+            return
         if self._mysql.is_unit_primary(self.unit_label):
             restart_states = {
                 self.restart_peers.data[unit].get("state", "unset") for unit in self.peers.units

src/upgrade.py

@@ -183,6 +183,11 @@ def _on_upgrade_granted(self, event: UpgradeGrantedEvent) -> None:  # noqa: C901
                 return
             self.charm.unit.status = MaintenanceStatus("check if upgrade is possible")
             self._check_server_upgradeability()
+            # override config, avoid restart
+            self.charm._mysql.write_mysqld_config(
+                profile=self.charm.config.profile,
+                memory_limit=self.charm.config.profile_limit_memory,
+            )
             self.charm.unit.status = MaintenanceStatus("starting services...")
             self.charm._mysql.start_mysqld()
             self.charm._mysql.setup_logrotate_and_cron()

tests/unit/test_upgrade.py

@@ -131,6 +131,7 @@ def test_pre_upgrade_prepare(
         mock_get_primary_label.assert_called_once()
         assert mock_set_dynamic_variable.call_count == 2
 
+    @patch("mysql_vm_helpers.MySQL.write_mysqld_config")
     @patch("upgrade.MySQLVMUpgrade._check_server_unsupported_downgrade")
     @patch("upgrade.MySQLVMUpgrade._reset_on_unsupported_downgrade")
     @patch("mysql_vm_helpers.MySQL.hold_if_recovering")
@@ -158,6 +159,7 @@ def test_upgrade_granted(
         mock_hold_if_recovering,
         mock_reset_on_unsupported_downgrade,
         mock_check_server_unsupported_downgrade,
+        mock_write_mysqld_config,
     ):
         """Test upgrade-granted hook."""
         self.charm.on.config_changed.emit()
@@ -176,6 +178,7 @@ def test_upgrade_granted(
         mock_install_workload.assert_called_once()
         mock_get_mysql_version.assert_called_once()
         mock_setup_logrotate_and_cron.assert_called_once()
+        mock_write_mysqld_config.assert_called_once()
 
         self.harness.update_relation_data(
             self.upgrade_relation_id, "mysql/0", {"state": "upgrading"}