db: logging option for cursor

In some cases we expect query to fail (LOCK NOWAIT) but it still
clutters the logs. Option for not logging cursor-level errors.

Fixes: https://pagure.io/koji/issue/2837

hub/kojihub.py

@@ -5421,10 +5421,13 @@ def _singleValue(query, values=None, strict=True):
         return None
 
 
-def _dml(operation, values):
-    """Run an insert, update, or delete. Return number of rows affected"""
+def _dml(operation, values, log=True):
+    """Run an insert, update, or delete. Return number of rows affected
+    If log is False, errors will not be logged. It makes sense only for
+    queries which are expected to fail (LOCK NOWAIT)
+    """
     c = context.cnx.cursor()
-    c.execute(operation, values)
+    c.execute(operation, values, log=log)
     ret = c.rowcount
     logger.debug("Operation affected %s row(s)", ret)
     c.close()

koji/db.py

@@ -132,7 +132,7 @@ class CursorWrapper:
                     params[i] = tuple(item)
         return sql, params
 
-    def execute(self, operation, parameters=()):
+    def execute(self, operation, parameters=(), log=True):
         debug = self.logger.isEnabledFor(logging.DEBUG)
         operation, parameters = self.preformat(operation, parameters)
         if debug:
@@ -141,7 +141,8 @@ class CursorWrapper:
         try:
             ret = self.cursor.execute(operation, parameters)
         except Exception:
-            self.logger.error('Query failed. Query was: %s', self.quote(operation, parameters))
+            if log:
+                self.logger.error('Query failed. Query was: %s', self.quote(operation, parameters))
             raise
         if debug:
             self.logger.debug("Execute operation completed in %.4f seconds", time.time() - start)

plugins/hub/protonmsg.py

@@ -356,7 +356,7 @@ def handle_db_msgs(urls, CONFIG):
     # we're running in postCommit, so we need to handle new transaction
     c.execute('BEGIN')
     try:
-        c.execute('LOCK TABLE proton_queue IN ACCESS EXCLUSIVE MODE NOWAIT')
+        c.execute('LOCK TABLE proton_queue IN ACCESS EXCLUSIVE MODE NOWAIT', log=False)
     except psycopg2.OperationalError:
         LOG.debug('skipping db queue due to lock')
         return