【MySQL案例】error.log的Warning：If a crash happens thisconfiguration does not guarantee that the relay lo（转）

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

【环境的叙述性说明】

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复制功能没有不论什么影响。

【报错原因】

         MySQL5.6版本号開始支持把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

         同一时候在MySQL5.6版本号中，添加了 Slave crash-safe replication功能，为了保证mysql的replication可以crash-safe。slave_master_info和slave_relay_log_info表必须使用事务型的存储引擎（InnoDB），不要尝试去手动改动这两张表的内容。

同一时候，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。同一时候开启relay_log_recovery功能。

         改动/etc/my.cnf配置文件，加入下面3项：

                   master-info-repository=table     # 能够使用set global 动态改动

                   relay-log-info-repository=table   # 能够使用setglobal 动态改动

                   relay-log-recovery=1           # 仅仅读參数，必须改动my.cnf重新启动mysql

         然后重新启动mysql实例。

【參考资料】

l  master.info和relay-log.info日志

         在复制的Slave节点上会创建两个日志，各自是master.infor和relay-log.info，位于datadir文件夹中。在MySQL5.6和兴许的版本号中，能够通过设置master-info-file和relay-log-info-file參数来指定写入到mysql的表中或者写入文件。

         这两个文件里包括一些类似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包括文件里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參数：

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，假设要获得slave的实时信息，能够查询slave_master_info和slave_relay_log_info表，或者运行show slave status查看。

l  master-info-repository

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

    假设设置为FILE。也是mysql的默认设置，Slave会在datadir/master.info文件里记录master的信息，从MySQL5.6版本号開始，建议使用TABLE模式。

l  relay-log-info-reposity

         relay-log-info-reposity=file|table。默认值是FILE。这个參数用于设置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。

    假设设置为FILE，也是mysql的默认设置，Slave会在datadir/master.info文件里记录master的信息，从MySQL5.6版本号開始，建议使用TABLE模式。

l  relay-log-recovery

         relay-log-recover=0|1，默认值是0不开启。该參数用于设置是否开启relay log的自己主动恢复功能。

当开启relay_log_recovery功能，slave数据库在启动的时候，会忽略未被运行的relay log。它会又一次连接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，能够有效避免slave运行了relay log里面的讹误记录。

         假设开启relay_log_recovery功能，我们有相同的时间到relay_log_info_reposity至TABLE状态。