Início / dba / Perguntas / 210839
Accepted
Sybil
Asked: 2018-06-29 03:25:55 +0800 CST

o que é MDL? (por exemplo, 'semântica MDL' ou 'bloqueios MDL') Provavelmente relacionado a Galera

  • 772

Encontrei um cara falando sobre semântica MDL em um relatório de bug Galera/XtraDB.

O que é MDL? O termo MDL também nos logs do Galera MDL conflict. Por favor, explique em detalhes.

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 respostas

  1. Best Answer

    Significa "MetaData Locking" vendo as fontes do MySQL https://dev.mysql.com/doc/dev/mysql-server/8.0.0/mdl_8h.html

    É uma forma de manter um banco de dados ACID evitando o acesso simultâneo aos mesmos dados. A ideia é que os metadados de uma tabela sejam "bloqueados" quando uma consulta dentro de uma transação utilizar essa tabela. Fazendo isso, outra transação não terá permissão para fazer consultas DDL nessas tabelas bloqueadas.

    Por exemplo, se você fizer um START TRANSACTIONentão SELECT * FROM tem um aplicativo cliente, os metadados da tabela tserão bloqueados. Nenhum outro cliente poderá fazer um ALTER TABLE t ...porque isso atrapalharia a estrutura da tabela enquanto a 1ª transação do cliente ainda estiver aberta.

    Mais informações no documento MySQL https://dev.mysql.com/doc/refman/5.5/en/metadata-locking.html

    • 3

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