X-Real-IP из запроса.x-real-ip, X-REAL-IP, X-ReAl-iP и т.п. 
SQL_Delay
The number of seconds that the replica must lag the source.
SQL_Remaining_Delay
When Replica_SQL_Running_State is Waiting until SOURCE_DELAY seconds after source executed event, this field contains the number of delay seconds remaining. At other times, this field is NULL.
man bash--signals the end of options and disables further option processing. Any arguments after the -- are treated as filenames and arguments. An argument of - is equivalent to --
-v с помощью grep в текстовом файле: grep -- -v file.txt, если не добавить --, то grep воспримет -v, как свою опцию, а не подстроку для поиска.