max_binlog_files，是Percona MySQL分支提供的限制binlog文件数量的参数，在删除归档数据、binlog增长很快的情况下，很实用的一个参数。

该参数也对正在被使用的binlog提供了保护，是purge不掉的，如下。

[root@mysql.sock][(none)]>purge binary logs to 'bin.016222';

Query OK, 0 rows affected, 1 warning (0.01 sec)

[root@mysql.sock][(none)]>>show warnings;

+---------+------+------------------------------------------------------------------------------------------------------+

| Level   | Code | Message                                                                                                        |

+---------+------+------------------------------------------------------------------------------------------------------+

| Warning | 1867 | file ./bin.016215 was not purged because it was being read by 1 thread(s), purged only 0 out of 7 files. |

+---------+------+------------------------------------------------------------------------------------------------------+

1 row in set (0.00 sec)

$ perror 1867

MySQL error code 1867 (ER_WARN_PURGE_LOG_IN_USE): file %s was not purged because it was being read by %d thread(s), purged only %d out of %d files.

error日志中也是用体现的。

2019-09-18T01:02:56.643574+08:00 10326541 [Warning] file ./bin.016215 was not purged because it was being readby thread number 17218543

2019-09-18T01:03:18.196285+08:00 17244031 [Warning] file ./bin.016215 was not purged because it was being readby thread number 17218543