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Sybil
Asked: 2018-06-29 03:25:55 +0800 CST

什么是 MDL？（例如“MDL 语义”或“MDL 锁”）可能与 Galera 相关

  • 772

我发现一个人在 Galera/XtraDB 错误报告中谈论MDL 语义。

什么是 MDL？术语 MDL 也在 Galera 日志MDL conflict中。请详细说明。

2018-06-14 17:07:10 140112699321088 [Note] WSREP: cluster conflict due to certification failure for threads:
2018-06-14 17:07:10 140112699321088 [Note] WSREP: Victim thread:
2018-06-14 17:07:10 140112690834176 [Note] WSREP: cluster conflict due to high priority abort for threads:
2018-06-14 17:07:10 140112690834176 [Note] WSREP: Winning thread:
2018-06-14 17:07:10 140112690834176 [Note] WSREP: Victim thread:
2018-06-14 17:07:10 140112690834176 [Note] WSREP: MDL conflict db=APC_MYSQLMON_DB table=TABLE1 ticket=4 solved by abort
2018-06-14 17:07:10 140112695683840 [Note] WSREP: MDL conflict db=APC_MYSQLMON_DB table=TABLE1 ticket=8 solved by abort
2018-06-14 17:07:10 140112695683840 [Note] WSREP: cluster conflict due to certification failure for threads:
2018-06-14 17:07:10 140112695683840 [Note] WSREP: Victim thread:
2018-06-14 17:26:47 140112698108672 [Note] WSREP: cluster conflict due to certification failure for threads:
2018-06-14 17:26:47 140112698108672 [Note] WSREP: Victim thread:


2018-06-14 17:34:48 140087340817152 [Note] WSREP: cluster conflict due to certification failure for threads:
2018-06-14 17:34:48 140087340817152 [Note] WSREP: Victim thread:
2018-06-14 17:36:48 140076554697472 [Note] WSREP: cluster conflict due to high priority abort for threads:
2018-06-14 17:36:48 140076554697472 [Note] WSREP: Winning thread:
2018-06-14 17:36:48 140076554697472 [Note] WSREP: Victim thread:
2018-06-14 17:36:48 140076554697472 [Note] WSREP: MDL conflict db=APC_MYSQLMON_DB table=TABLE1 ticket=4 solved by abort
2018-06-14 17:36:48 140087340817152 [Note] WSREP: MDL conflict db=APC_MYSQLMON_DB table=TABLE1 ticket=8 solved by abort
2018-06-14 17:36:48 140087340817152 [Note] WSREP: cluster conflict due to certification failure for threads:
2018-06-14 17:36:48 140087340817152 [Note] WSREP: Victim thread:


2018-06-14 17:37:50 139917573339904 [Note] WSREP: cluster conflict due to certification failure for threads:
2018-06-14 17:37:50 139917573339904 [Note] WSREP: Victim thread:

2018-06-14 17:05:12 139927950939904 [Warning] WSREP: Failed to report last committed 1941199495, -4 (Interrupted system call)
2018-06-14 17:09:41 139900840323840 [Note] WSREP: cluster conflict due to high priority abort for threads:
2018-06-14 17:09:41 139900840323840 [Note] WSREP: Winning thread:
2018-06-14 17:09:41 139900840323840 [Note] WSREP: Victim thread:
mysql mariadb

1 个回答

  1. Best Answer

    它代表“元数据锁定”查看 MySQL https://dev.mysql.com/doc/dev/mysql-server/8.0.0/mdl_8h.html的来源

    这是一种通过避免并发访问相同数据来保持 ACID 数据库的方法。这个想法是，当事务中的查询使用该表时，表的元数据被“锁定”。这样做，将不允许另一个事务对这些锁定的表执行 DDL 查询。

    例如，如果您在一个客户端应用程序中执行START TRANSACTION然后SELECT * FROM t，则表的元数据将t被锁定。没有其他客户端能够执行此操作，ALTER TABLE t ...因为它会在第一个客户端事务仍然打开时弄乱表结构。

    MySQL 文档中的更多信息https://dev.mysql.com/doc/refman/5.5/en/metadata-locking.html

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