MySQL5.7主从从配置

主从从，也称为级联主从，数据流向：A(主)->B(从)->C(从从)，主从从级联复制。

应用场景

• 在主从配置的基础上，再增加一个从库，进一步提高数据安全，容灾备份。
• 读写分离，从库只用于查询，提高数据库整体性能。
• 从从库，用于备份，等同在线实时增量备份。

部署环境

​ 注：使用docker部署mysql实例，方便快速搭建演示环境。但本文重点是讲解主从配置，因此简略描述docker环境构建mysql容器实例。

• 数据库：MySQL 5.7.x （相比5.5，5.6而言，5.7同步性能更好，支持多源复制，可实现多主一从，主从库版本应保证一致）
• 操作系统：CentOS 7.x
• 容器：Docker 17.09.0-ce
• 镜像：mysql:5.7
• 主库：IP=192.168.10.212; PORT=4200; server-id=200; database=test; table=user
• 从库：IP=192.168.10.212; PORT=4211; server-id=210; database=test; table=user
• 从从库：IP=192.168.10.212; PORT=4211; server-id=211; database=test; table=userk

配置约束

• 主从库必须保证网络畅通可访问
• 主库必须开启binlog日志
• 主从库的server-id必须不同

事前准备

1. 关闭selinux

setenforce 0
vim /etc/sysconfig/selinux 
SELINUX=disabled

# 若不关闭，使用docker启动mysql5.7镜像容器时启动不起来，查看日志会有如下错误显示：
ERROR: mysqld failed while attempting to check config
command was: "mysqld --verbose --help"
mysqld: Can't read dir of '/etc/mysql/conf.d/' (Errcode: 13 - Permission denied)
mysqld: [ERROR] Fatal error in defaults handling. Program aborted!
ERROR: mysqld failed while attempting to check config
command was: "mysqld --verbose --help"
mysqld: Can't read dir of '/etc/mysql/conf.d/' (Errcode: 13 - Permission denied)
mysqld: [ERROR] Fatal error in defaults handling. Program aborted!

2. 安装并启动docker

yum install epel-release
yum -y install docker
systemctl start docker.service

3. 创建目录

mkdir -p /datavol/mysql-200/{mysql,conf}
mkdir -p /datavol/mysql-210/{mysql,conf}
mkdir -p /datavol/mysql-211/{mysql,conf}

【主库】操作及配置

把该文件放到主库所在配置文件路径下：/datavol/mysql-200/conf

配置my.cnf

[client]
port = 3306
default-character-set = utf8mb4

[mysql]
port = 3306
default-character-set = utf8mb4

[mysqld]
##########################
# summary
##########################
#bind-address = 0.0.0.0
#port = 3306
#datadir=/datavol/mysql/data #数据存储目录

##########################
# log bin
##########################
server-id = 200				#必须唯一
log_bin = mysql-bin 		#开启及设置二进制日志文件名称
binlog_format = MIXED
sync_binlog = 1
expire_logs_days =7			#二进制日志自动删除/过期的天数。默认值为0，表示不自动删除。

#binlog_cache_size = 128m
#max_binlog_cache_size = 512m
#max_binlog_size = 256M

binlog-do-db = test 		#要同步的数据库 

binlog-ignore-db = mysql 	#不需要同步的数据库 
binlog_ignore_db = information_schema
binlog_ignore_db = performation_schema
binlog_ignore_db = sys
			

##########################
# character set
##########################
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci

安装启动主库

[root@localhost ~]# docker run -d -p 4200:3306 --name=mysql-200 -v /datavol/mysql-200/conf:/etc/mysql/conf.d -v /datavol/mysql-200:/datavol/mysql -e MYSQL_ROOT_PASSWORD=123456 mysql:5.7
5691bac538e646db00273e3cad5b350dbe6cce0bd176346b7eefd9a6f9e3a9ad
[root@localhost ~]# docker ps
CONTAINER ID        IMAGE                               COMMAND                  CREATED             STATUS              PORTS                                                NAMES
5691bac538e6        mysql:5.7                           "docker-entrypoint..."   44 seconds ago      Up 43 seconds       33060/tcp, 0.0.0.0:4200->3306/tcp                    mysql-200
[root@localhost ~]# docker exec -it mysql-200 /bin/bash
root@5691bac538e6:/# mysql -u root -p
Enter password: 

注：若不熟悉docker，可使用传统方式安装mysql，效果相同。

创建授权用户

连接mysql主数据库，键入命令mysql -u root -p，输入密码后登录数据库。创建用户用于从库同步复制，授予复制、同步访问的权限

mysql> CREATE USER 'slave'@'%' IDENTIFIED BY '123456';
Query OK, 0 rows affected (0.01 sec)

mysql> GRANT REPLICATION SLAVE, REPLICATION CLIENT ON *.* TO 'slave'@'%';
Query OK, 0 rows affected (0.00 sec)

log_bin是否开启

mysql> show variables like 'log_bin';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| log_bin       | ON    |
+---------------+-------+
1 row in set

查看master状态

mysql> show master status;
+------------------+----------+--------------+--------------------------------------------------+-------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB                                 | Executed_Gtid_Set |
+------------------+----------+--------------+--------------------------------------------------+-------------------+
| mysql-bin.000001 |     154  | test         | mysql,information_schema,performation_schema,sys |                   |
+------------------+----------+--------------+--------------------------------------------------+-------------------+
1 row in set

【从库】配置及操作

配置my.cnf

把该文件放到主库所在配置文件路径下：/datavol/mysql-210/conf/

[client]
port = 3306
default-character-set = utf8mb4

[mysql]
port = 3306
default-character-set = utf8mb4

[mysqld]
##########################
# summary
##########################
#bind-address = 0.0.0.0
#port = 3306
#datadir=/datavol/mysql/data #数据存储目录

##########################
# log bin
##########################
server-id = 210				#必须唯一
log_bin = mysql-bin 		#开启及设置二进制日志文件名称
binlog_format = MIXED
sync_binlog = 1
expire_logs_days =7			#二进制日志自动删除/过期的天数。默认值为0，表示不自动删除。
log_slave_updates = 1 		#【关键点】从主服务器接收到的更新同时要写入二进制日志

#binlog_cache_size = 128m
#max_binlog_cache_size = 512m
#max_binlog_size = 256M

binlog-do-db = test 		#要同步的数据库 

binlog-ignore-db = mysql 	#不需要同步的数据库 
binlog_ignore_db = information_schema
binlog_ignore_db = performation_schema
binlog_ignore_db = sys
			

##########################
# character set
##########################
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci

**log_slave_updates = 1 ** #【关键点】从主服务器接收到的更新同时要写入二进制日志

安装启动从库

[root@localhost ~]# docker run -d -p 4210:3306 --name=mysql-210 -v /datavol/mysql-210/conf:/etc/mysql/conf.d -v /datavol/mysql-210:/datavol/mysql -e MYSQL_ROOT_PASSWORD=123456 mysql:5.7
19e93b6d93ca4e6ca0d540e3f6c831b835cdbb35362733867c3977aee4d33bf7
[root@localhost ~]# docker ps
CONTAINER ID        IMAGE                               COMMAND                  CREATED             STATUS              PORTS                                                NAMES
19e93b6d93ca        mysql:5.7                           "docker-entrypoint..."   4 seconds ago       Up 3 seconds        33060/tcp, 0.0.0.0:4210->3306/tcp                    mysql-210
[root@localhost ~]# docker exec -it mysql-210 /bin/bash
root@19e93b6d93ca:/# mysql -u root -p
Enter password: 

设置主库200信息

登录【从数据库】，进入mysql命令行。

mysql> stop slave;
Query OK, 0 rows affected

mysql> CHANGE MASTER TO 
MASTER_HOST='192.168.10.212',
MASTER_PORT=4200,
MASTER_USER='slave',
MASTER_PASSWORD='123456',
MASTER_LOG_FILE='mysql-bin.000001',
MASTER_LOG_POS=154;
Query OK, 0 rows affected

mysql> start slave;
Query OK, 0 rows affected

stop slave; //停止同步
start slave; //开始同步
//必须和【主数据库】的信息匹配。
CHANGE MASTER TO
MASTER_HOST='192.168.10.212', //主库IP
MASTER_PORT=4200, //主库端口
MASTER_USER='slave', //访问主库且有同步复制权限的用户
MASTER_PASSWORD='123456', //登录密码
//【关键处】从主库的该log_bin文件开始读取同步信息，主库show master status返回结果
MASTER_LOG_FILE='mysql-bin.000001',
//【关键处】从文件中指定位置开始读取，主库show master status返回结果
MASTER_LOG_POS=154;

查看同步状态

mysql> show slave status \G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.10.212
                  Master_User: slave
                  Master_Port: 4200
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000003
          Read_Master_Log_Pos: 617
               Relay_Log_File: 5f0d9861bcb1-relay-bin.000002
                Relay_Log_Pos: 320
        Relay_Master_Log_File: mysql-bin.000003
             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: 617
              Relay_Log_Space: 534
              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: 200
                  Master_UUID: b6df98cf-e71f-11e8-9987-0242ac110007
             Master_Info_File: /var/lib/mysql/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 
     Last_SQL_Error_Timestamp: 
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 
            Executed_Gtid_Set: 
                Auto_Position: 0
         Replicate_Rewrite_DB: 
                 Channel_Name: 
           Master_TLS_Version: 
1 row in set (0.00 sec)

只有【Slave_IO_Running】和【Slave_SQL_Running】都是Yes，则同步是正常的。
如果是No或者Connecting都不行，可查看mysql-error.log，以排查问题。

mysql> show variables like 'log_error%';
+---------------------+--------+
| Variable_name       | Value  |
+---------------------+--------+
| log_error           | stderr |
| log_error_verbosity | 3      |
+---------------------+--------+
2 rows in set

配置完成，则主从数据库开始自动同步。此外，【从库】相当于【从从库】的主库，也需要设置账号及同步权限。

创建授权用户

创建用户用于从库同步复制，授予复制、同步访问的权限

mysql> CREATE USER 'slave'@'%' IDENTIFIED BY '123456';
Query OK, 0 rows affected (0.01 sec)

mysql> GRANT REPLICATION SLAVE, REPLICATION CLIENT ON *.* TO 'slave'@'%';
Query OK, 0 rows affected (0.00 sec)

log_bin是否开启

mysql> show variables like 'log_bin';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| log_bin       | ON    |
+---------------+-------+
1 row in set

查看master状态

mysql> show master status;
+------------------+----------+--------------+--------------------------------------------------+-------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB                                 | Executed_Gtid_Set |
+------------------+----------+--------------+--------------------------------------------------+-------------------+
| mysql-bin.000003 |     617  | test         | mysql,information_schema,performation_schema,sys |                   |
+------------------+----------+--------------+--------------------------------------------------+-------------------+
1 row in set

【从从库】配置及操作

配置my.cnf

把该文件放到主库所在配置文件路径下：/datavol/mysql-211/conf/

[client]
port = 3306
default-character-set = utf8mb4

[mysql]
port = 3306
default-character-set = utf8mb4

[mysqld]
##########################
# summary
##########################
#bind-address = 0.0.0.0
#port = 3306
#datadir=/datavol/mysql/data 	#数据存储目录

##########################
# log bin
##########################
server-id = 211
		

##########################
# character set
##########################
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci

安装启动从从库

[root@localhost ~]# docker run -d -p 4211:3306 --name=mysql-211 -v /datavol/mysql-211/conf:/etc/mysql/conf.d -v /datavol/mysql-211:/datavol/mysql -e MYSQL_ROOT_PASSWORD=123456 mysql:5.7
19e93b6d93ca4e6ca0d540e3f6c831b835cdbb35362733867c3977aee4d33bf7
[root@localhost ~]# docker ps
CONTAINER ID        IMAGE                               COMMAND                  CREATED             STATUS              PORTS                                                NAMES
19e93b6d93ca        mysql:5.7                           "docker-entrypoint..."   4 seconds ago       Up 3 seconds        33060/tcp, 0.0.0.0:4211->3306/tcp                    mysql-211
[root@localhost ~]# docker exec -it mysql-211 /bin/bash
root@19e93b6d93ca:/# mysql -u root -p
Enter password: 

设置从库210信息

登录【从数据库】，进入mysql命令行。

mysql> stop slave;
Query OK, 0 rows affected

mysql> CHANGE MASTER TO MASTER_HOST='192.168.10.212',
MASTER_PORT=4210,
MASTER_USER='slave',
MASTER_PASSWORD='123456',
MASTER_LOG_FILE='mysql-bin.000003',
MASTER_LOG_POS=617;
Query OK, 0 rows affected

mysql> start slave;
Query OK, 0 rows affected

stop slave; //停止同步
start slave; //开始同步
//必须和【主数据库】的信息匹配。
CHANGE MASTER TO
MASTER_HOST='192.168.10.212', //主库IP
MASTER_PORT=4210, //主库端口(在这里是指从库)
MASTER_USER='slave', //访问主库且有同步复制权限的用户
MASTER_PASSWORD='123456', //登录密码
//【关键处】从主库的该log_bin文件开始读取同步信息，主库show master status返回结果
MASTER_LOG_FILE='mysql-bin.000003',
//【关键处】从文件中指定位置开始读取，主库show master status返回结果
MASTER_LOG_POS=617;

查看同步状态

mysql> show slave status \G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.10.212
                  Master_User: slave
                  Master_Port: 4210
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000003
          Read_Master_Log_Pos: 617
               Relay_Log_File: a3d52e314640-relay-bin.000002
                Relay_Log_Pos: 783
        Relay_Master_Log_File: mysql-bin.000003
             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: 617
              Relay_Log_Space: 997
              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: 210
                  Master_UUID: 088c2c93-e720-11e8-8e80-0242ac110009
             Master_Info_File: /var/lib/mysql/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 
     Last_SQL_Error_Timestamp: 
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 
            Executed_Gtid_Set: 
                Auto_Position: 0
         Replicate_Rewrite_DB: 
                 Channel_Name: 
           Master_TLS_Version: 
1 row in set (0.00 sec)

只有【Slave_IO_Running】和【Slave_SQL_Running】都是Yes，则同步是正常的。
如果是No或者Connecting都不行，可查看mysql-error.log，以排查问题。

mysql> show variables like 'log_error%';
+---------------------+--------+
| Variable_name       | Value  |
+---------------------+--------+
| log_error           | stderr |
| log_error_verbosity | 3      |
+---------------------+--------+
2 rows in set

配置完成，则从从数据库开始自动同步。

验证数据同步

建库

使用root账号登录【主服务器】，创建test数据库

mysql> CREATE DATABASE test;
Query OK, 1 row affected (0.00 sec)

mysql> USE test;
Database changed

建表

在【主库】中创建user表

CREATE TABLE `user` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `name` varchar(20) COLLATE utf8mb4_unicode_ci NOT NULL,
  `age` tinyint(3) unsigned NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

新增

在【主库】中向user表插入一条数据：

mysql> use test;
Database changed
mysql> INSERT INTO user (id, name, age) VALUES (1, '张三', 18);
Database changed
mysql> SELECT * FROM user;
+----+------+-----+
| id | name | age |
+----+------+-----+
|  1 | 张三 |  18 |
+----+------+-----+
1 row in set

在【从库】及【从从库】中查询user表数据：

mysql> use test;
Database changed
mysql> SELECT * FROM user;
+----+------+-----+
| id | name | age |
+----+------+-----+
|  1 | 张三 |  18 |
+----+------+-----+
1 row in set

新增记录同步成功。

更新

在【主库】中修改刚才插入的数据：

mysql> UPDATE user SET name='李四' where id=1;
Database changed
Rows matched: 1  Changed: 1  Warnings: 0
mysql> SELECT * FROM user;
+----+------+-----+
| id | name | age |
+----+------+-----+
|  1 | 李四 |  18 |
+----+------+-----+
1 row in set

在【从库】及【从从库】中查询user表数据：

mysql> SELECT * FROM user;
+----+------+-----+
| id | name | age |
+----+------+-----+
|  1 | 李四 |  18 |
+----+------+-----+
1 row in set

更新记录同步成功。

删除

在【主库】中删除刚才更新的数据：

mysql> DELETE FROM user WHERE id=1;
Database changed
mysql> SELECT * FROM user;
Empty set

在【从库】及【从从库】中查询user表数据：

mysql> SELECT * FROM user;
Empty set

删除记录同步成功。

补充：

• 如果【主服务器】重启mysql服务，【从服务器】会等待与【主服务器】重连。当主服务器恢复正常后，从服务器会自动重新连接上主服务器，并正常同步数据。
• 如果某段时间内，【从数据库】服务器异常导致同步中断（可能是同步点位置不匹配），可以尝试以下恢复方法：进入【主数据库】服务器（正常），在bin-log中找到【从数据库】出错前的position，然后在【从数据库】上执行change master，将master_log_file和master_log_pos重新指定后，开始同步。