详解MySQL主从复制实战 - 基于日志点的复制
Payon 人气:0基于日志点的复制
1、在主库与从库上建立专用的复制账号
MariaDB [employees]> create user 'repl'@'172.%' identified by '123456';
注意在生产上的密码必须依照相关规范以达到一定的密码强度, 并且规定在从库上的特定网段上才能访问主库
2、在主库与从库上授予复制权限
MariaDB [employees]> grant replication slave on *.* to 'repl'@'172.%';
3、配置主库
注意启用二进制日志需要重启服务, 而server_id是一个动态参数, 可以结合命令行与配置文件以达到免重启的持久化配置. 注意server_id在集群中是唯一的.
[mysqld] log_bin = /var/log/mysql/mariadb-bin log_bin_index = /var/log/mysql/mariadb-bin.index binlog_format = row server_id = 101
NOTE: 把日志与数据分开是个好习惯, 最好能放到不同的数据分区
4、配置从库
选项log_slave_update决定是否把中继日志relay_log存放到本机的binlog中, 如果是配置链路复制, 那么该选项必填. 注意server_id在集群中是唯一的.
[mysqld] # replication log_bin = /var/log/mysql/mariadb-bin log_bin_index = /var/log/mysql/mariadb-bin.index server_id = 102 # slaves relay_log = /var/log/mysql/relay-bin relay_log_index = /var/log/mysql/relay-bin.index relay_log_info_file = /var/log/mysql/relay-bin.info log_slave_updates = ON read_only
5、初始化从库的数据
此处使用mysqldump在主库上进行备份, 在生产上建议大家用xtrabackup进行无锁的热备(基于innodb引擎).
备份主库上的employees数据库的数据
mysqldump --single-transaction --master-data=1 --triggers --routines --databases employees -u root -p >> backup.sql
将备份文件backup.sql通过scp或者docker volume卷挂载到从服务器上, 并且导入至从库中
mysql -u root -p < backup.sql
6、启动复制链路
现有master@172.20.0.2和slave@172.20.0.3, 并且已经通过mysqldump将数据同步至从库slave中. 现在在从服务器slave上配置复制链路
MariaDB [(none)]> CHANGE MASTER TO MASTER_HOST='master', MASTER_USER='repl', MASTER_PASSWORD='123456', MASTER_LOG_FILE='mariadb-bin.000029', MASTER_LOG_POS=516; Query OK, 0 rows affected (0.02 sec)
在从库上启动复制链路
MariaDB [(none)]> start slave; Query OK, 0 rows affected (0.01 sec)
7、在从库上检查slave状态
Slave_IO_Running与Slave_SQL_Running必须为YES, 如果出现错误须详细阅读Last_IO_Error或Last_SQL_Error的提示信息
MariaDB [(none)]> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: master
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mariadb-bin.000029
Read_Master_Log_Pos: 516
Relay_Log_File: relay-bin.000002
Relay_Log_Pos: 539
Relay_Master_Log_File: mariadb-bin.000029
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 516
Relay_Log_Space: 831
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 101
Master_SSL_Crl:
Master_SSL_Crlpath:
Using_Gtid: No
Gtid_IO_Pos:
Replicate_Do_Domain_Ids:
Replicate_Ignore_Domain_Ids:
Parallel_Mode: conservative
1 row in set (0.00 sec)
8、在主库检查dump线程
检测是否已经正确启动binlog dump线程
MariaDB [(none)]> show processlist \G *************************** 1. row *************************** Id: 7 User: root Host: 172.20.0.1:41868 db: employees Command: Sleep Time: 56 State: Info: NULL Progress: 0.000 *************************** 2. row *************************** Id: 10 User: repl Host: 172.20.0.3:45974 db: NULL Command: Binlog Dump Time: 246 State: Master has sent all binlog to slave; waiting for binlog to be updated Info: NULL Progress: 0.000
可以看到row 2上有Command为Binlog Dump的命令被启动, 证明复制线程已经被成功启动
9、总结
优点
- 技术成熟, BUG相对较少
- 对SQL查询没有任何限制, 如基于GTID复制时不是所有SQL都可以使用
缺点
- 故障转移时重新获取新主的日志偏移量较为困难
在一主多从环境下, 若旧master宕机后在集群中选举出新master, 其他的从库要对这个新的master进行重新同步, 由于每个DB的binlog都是独立存在, 所以很难找出开始同步的日志点
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