【MySQL案例】error.log的Warning：If a crash happens thisconf_MySQL

1.1.1. If a crash happens thisconfiguration does not guarantee that the relay log info will be consistent

【环境描述】

msyql5.6.14

【报错信息】

mysql的slave启动时，error.log中出现Warning警告：

[Warning] Slave SQL: If a crash happensthis configuration does not guarantee that the relay log info will beconsistent, Error_code: 0

这条Warning信息对Mysql和MySQL复制功能没有任何影响。

【报错原因】

MySQL5.6版本开始支持把master.info和relay-log.info的内容写入到mysql库的表中，

master.info--> mysql.slave_master_info

relay-log.info--> mysql. slave_relay_log_info

同时在MySQL5.6版本中，增加了Slave crash-safe replication功能，为了保证mysql的replication能够crash-safe，slave_master_info和slave_relay_log_info表必须使用事务型的存储引擎（InnoDB），不要尝试去手动修改这两张表的内容。同时，Slave还要开启relay_log_recovery功能。

【解决方法】

设置master_info_repository和relay_log_info_repository的值为TABLE，同时开启relay_log_recovery功能。

修改/etc/my.cnf配置文件，添加以下3项：

master-info-repository=table     # 可以使用set global 动态修改

relay-log-info-repository=table   # 可以使用setglobal 动态修改

relay-log-recovery=1           # 只读参数，必须修改my.cnf重启mysql

然后重启mysql实例。

【参考资料】

lmaster.info和relay-log.info日志

在复制的Slave节点上会创建两个日志，分别是master.infor和relay-log.info，位于datadir目录中。在MySQL5.6和后续的版本中，可以通过设置master-info-file和relay-log-info-file参数来指定写入到mysql的表中或者写入文件。

这两个文件中包含一些类似showslave status输出的信息，当slave启动的时候会读取master.info和relay-log.info文件来确定从master读取binary log和读取relay log的信息。

Slave的I/O线程负责更新维护master.info文件，

master.info	mysql.slave_master_info	SHOW SLAVE STATUS Column	Description
1	Number_of_lines	[None]	Number of lines in the file
2	Master_log_name	Master_Log_File	The name of the master binary log currently being read from the master
3	Master_log_pos	Read_Master_Log_Pos	The current position within the master binary log that have been read from the master
4	Host	Master_Host	The host name of the master
5	User	Master_User	The user name used to connect to the master
6	User_password	Password (not shown by SHOW SLAVE STATUS)	The password used to connect to the master
7	Port	Master_Port	The network port used to connect to the master
8	Connect_retry	Connect_Retry	The period (in seconds) that the slave will wait before trying to reconnect to the master
9	Enabled_ssl	Master_SSL_Allowed	Indicates whether the server supports SSL connections
10	Ssl_ca	Master_SSL_CA_File	The file used for the Certificate Authority (CA) certificate
11	Ssl_capath	Master_SSL_CA_Path	The path to the Certificate Authority (CA) certificates
12	Ssl_cert	Master_SSL_Cert	The name of the SSL certificate file
13	Ssl_cipher	Master_SSL_Cipher	The list of possible ciphers used in the handshake for the SSL connection
14	Ssl_key	Master_SSL_Key	The name of the SSL key file
15	Ssl_verify_server_cert	Master_SSL_Verify_Server_Cert	Whether to verify the server certificate
16	Heartbeat	[None]	Interval between replication heartbeats, in seconds
17	Bind	Master_Bind	Which of the slave's network interfaces should be used for connecting to the master
18	Ignored_server_ids	Replicate_Ignore_Server_Ids	The number of server IDs to be ignored, followed by the actual server IDs
19	Uuid	Master_UUID	The master's unique ID
20	Retry_count	Master_Retry_Count	Maximum number of reconnection attempts permitted Added in MySQL 5.6.1)

Slave的SQL线程负责维护relay-log.info文件，在MySQL5.6中relay-log.info包含文件中的记录数和复制延迟的秒数。

relaylog.info	slave_relay_log_info	SHOW SLAVE STATUS	Description
1	Number_of_lines	[None]	Number of lines in the file or rows in the table
2	Relay_log_name	Relay_Log_File	The name of the current relay log file
3	Relay_log_pos	Relay_Log_Pos	The current position within the relay log file; events up to this position have been executed on the slave database
4	Master_log_name	Relay_Master_Log_File	The name of the master binary log file from which the events in the relay log file were read
5	Master_log_pos	Exec_Master_Log_Pos	The equivalent position within the master's binary log file of events that have already been executed
6	Sql_delay	SQL_Delay	The number of seconds that the slave must lag the master

设置master_info_repository和relay_log_info_repository参数：

SQL> stop slave;

SQL> set global master_info_repository=table;

SQL> set global relay_log_info_repository=table;

SQL> show variables like '%repository';

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

| Variable_name           | Value |

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

| master_info_repository    | TABLE |

| relay_log_info_repository  | TABLE |

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

查看向Master读取日志的情况：

SQL> select * from slave_master_info;

查看Slave的Relay日志应用情况：

SQL> select * from slave_relay_log_info;

注意：

         master.info和relay-log.info内的数据会有一定的延迟，取决于mysql把slave信息刷到硬盘的时间，如果要获得slave的实时信息，可以查询slave_master_info和slave_relay_log_info表，或者执行show slave status查看。

l  master-info-repository

master-info-repository={ FILE | TABLE }，默认值是FILE，这个参数用于设置Slave节点上把master的信息写入到物理文件中还是写入到mysql. slave_master_info表中。

如果设置为FILE，也是mysql的默认设置，Slave会在datadir/master.info文件中记录master的信息，从MySQL5.6版本开始，建议使用TABLE模式。

l  relay-log-info-reposity

relay-log-info-reposity=file|table，默认值是FILE，这个参数用于设置slave节点上把relay-log.info的信息写入到datadir/relay-log.info文件或者mysql. slave_relay_log_info表。

如果设置为FILE，也是mysql的默认设置，Slave会在datadir/master.info文件中记录master的信息，从MySQL5.6版本开始，建议使用TABLE模式。

l  relay-log-recovery

relay-log-recover=0|1，默认值是0不开启，该参数用于设置是否开启relay log的自动恢复功能。当开启relay_log_recovery功能，slave数据库在启动的时候，会忽略未被执行的relay log，它会重新连接master获取relay log来进行恢复。

当slave发生宕机的时候，建议开启该功能，可以有效避免slave执行了relay log里面的讹误记录。

如果开启relay_log_recovery功能，必须同时把relay_log_info_reposity设置为TABLE模式。