Check for final setting enabled in clickhouse (#21)

mysql_ch_replicator/clickhouse_api.py

@@ -187,3 +187,9 @@ def select(self, table_name, where=None):
         for row in rows:
             results.append(dict(zip(columns, row)))
         return results
+
+    def get_system_setting(self, name):
+        results = self.select('system.settings', f"name = '{name}'")
+        if not results:
+            return None
+        return results[0].get('value', None)

mysql_ch_replicator/db_replicator.py

@@ -136,9 +136,21 @@ def __init__(self, config: Settings, database: str, target_database: str = None,
     def create_state(self):
         return State(os.path.join(self.config.binlog_replicator.data_dir, self.database, 'state.pckl'))
 
+    def validate_database_settings(self):
+        if not self.initial_only:
+            final_setting = self.clickhouse_api.get_system_setting('final')
+            if final_setting != '1':
+                logger.warning('settings validation failed')
+                logger.warning(
+                    '\n\n\n    !!!  WARNING - MISSING REQUIRED CLICKHOUSE SETTING  (final)  !!!\n\n'
+                    'You need to set <final>1</final> in clickhouse config file\n'
+                    'Otherwise you will get DUPLICATES in your SELECT queries\n\n\n'
+                )
+
     def run(self):
         try:
             logger.info('launched db_replicator')
+            self.validate_database_settings()
 
             if self.state.status != Status.NONE:
                 # ensure target database still exists