DPE-5628 Skip set unknown config keys

src/charm.py

@@ -276,9 +276,6 @@ def _on_config_changed(self, _) -> None:
             # the upgrade already restart the daemon
             return
 
-        # restart not required if mysqld is not running
-        mysqld_running = self._mysql.is_mysqld_running()
-
         previous_config = self.mysql_config.custom_config
         if not previous_config:
             # empty config means not initialized, skipping
@@ -298,30 +295,33 @@ def _on_config_changed(self, _) -> None:
 
         changed_config = compare_dictionaries(previous_config, new_config_dict)
 
-        if self.mysql_config.keys_requires_restart(changed_config):
-            # there are static configurations in changed keys
-            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
-            )
-            if mysqld_running:
-                logger.info("Configuration change requires restart")
+        logger.info("Persisting configuration changes to file")
+        # always persist config to file
+        self._mysql.write_content_to_file(
+            path=MYSQLD_CUSTOM_CONFIG_FILE, content=new_config_content
+        )
 
-                if "loose-audit_log_format" in changed_config:
-                    # plugins are manipulated running daemon
-                    if self.config.plugin_audit_enabled:
-                        self._mysql.install_plugins(["audit_log", "audit_log_filter"])
-                    else:
-                        self._mysql.uninstall_plugins(["audit_log", "audit_log_filter"])
+        if (
+            self.mysql_config.keys_requires_restart(changed_config)
+            and self._mysql.is_mysqld_running()
+        ):
+            logger.info("Configuration change requires restart")
+            if "loose-audit_log_format" in changed_config:
+                # plugins are manipulated on running daemon
+                if self.config.plugin_audit_enabled:
+                    self._mysql.install_plugins(["audit_log", "audit_log_filter"])
+                else:
+                    self._mysql.uninstall_plugins(["audit_log", "audit_log_filter"])
 
-                self.on[f"{self.restart.name}"].acquire_lock.emit()
-                return
+            self.on[f"{self.restart.name}"].acquire_lock.emit()
 
-        if dynamic_config := self.mysql_config.filter_static_keys(changed_config):
+        elif dynamic_config := self.mysql_config.filter_static_keys(changed_config):
             # if only dynamic config changed, apply it
             logger.info("Configuration does not requires restart")
             for config in dynamic_config:
+                if config not in new_config_dict:
+                    # skip removed configs
+                    continue
                 self._mysql.set_dynamic_variable(config, new_config_dict[config])
 
     def _on_start(self, event: StartEvent) -> None:

tests/integration/high_availability/test_upgrade_skip_pre_upgrade_check.py

@@ -3,6 +3,7 @@
 
 import asyncio
 import logging
+import subprocess
 from time import sleep
 
 import pytest
@@ -71,7 +72,37 @@ async def test_refresh_without_pre_upgrade_check(ops_test: OpsTest):
     #   2. Rolling restart, if there's a configuration change
     # for both, operations should continue to work
     # and there's a mismatch between the charm and the snap
-    logger.info("Wait for rolling restart OR continue to writes")
+    logger.info("Wait (120s) for rolling restart OR continue to writes")
+    count = 0
+    while count < 2 * 60:
+        if "maintenance" in {unit.workload_status for unit in application.units}:
+            # Case when refresh triggers a rolling restart
+            logger.info("Waiting for rolling restart to complete")
+            await ops_test.model.wait_for_idle(
+                apps=[MYSQL_APP_NAME], status="active", idle_period=30, timeout=TIMEOUT
+            )
+            break
+        else:
+            count += 1
+            sleep(1)
+
+    await ensure_all_units_continuous_writes_incrementing(ops_test)
+
+
+@pytest.mark.group(1)
+@markers.amd64_only  # TODO: remove after arm64 stable release
+async def test_rollback_without_pre_upgrade_check(ops_test: OpsTest):
+    """Test refresh back to stable channel."""
+    application = ops_test.model.applications[MYSQL_APP_NAME]
+
+    logger.info("Refresh the charm back to stable channel")
+    # pylibjuju refresh dont work for switch:
+    # https://github.com/juju/python-libjuju/issues/924
+    subprocess.check_output(
+        f"juju refresh {MYSQL_APP_NAME} --switch ch:{MYSQL_APP_NAME} --channel 8.0/stable".split()
+    )
+
+    logger.info("Wait (120s) for rolling restart OR continue to writes")
     count = 0
     while count < 2 * 60:
         if "maintenance" in {unit.workload_status for unit in application.units}:
@@ -85,5 +116,4 @@ async def test_refresh_without_pre_upgrade_check(ops_test: OpsTest):
             count += 1
             sleep(1)
 
-    logger.info("Ensure continuous_writes")
     await ensure_all_units_continuous_writes_incrementing(ops_test)