DPE-3896 report_host as static config (#435)

* report_host is static config

* refactor flow to avoid event deferral

Author: paulomach

src/charm.py

@@ -452,7 +452,7 @@ def _on_peer_relation_joined(self, _) -> None:
         self.unit_peer_data.setdefault("member-role", "unknown")
         self.unit_peer_data.setdefault("member-state", "waiting")
 
-    def _on_config_changed(self, event: EventBase) -> None:
+    def _on_config_changed(self, _: EventBase) -> None:
         """Handle the config changed event."""
         if not self._is_peer_data_set:
             # skip when not initialized
@@ -463,12 +463,6 @@ 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
-
         config_content = self._mysql.read_file_content(MYSQLD_CONFIG_FILE)
         if not config_content:
             # empty config means not initialized, skipping
@@ -492,8 +486,11 @@ def _on_config_changed(self, event: EventBase) -> None:
 
             # persist config to file
             self._mysql.write_content_to_file(path=MYSQLD_CONFIG_FILE, content=new_config_content)
-            self.on[f"{self.restart.name}"].acquire_lock.emit()
-            return
+
+            if self._mysql.is_mysqld_running():
+                # restart the service
+                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

src/config.py

@@ -24,6 +24,7 @@ class MySQLConfig:
         "innodb_buffer_pool_chunk_size",
         "group_replication_message_cache_size",
         "log_error",
+        "report_host",
     }
 
     def keys_requires_restart(self, keys: set) -> bool: