基于 MySQL 自带工具 mysqld_multi 实现主从复制

写在前面

正常情况是准备需要主从个数的服务器，每个服务器都安装好 mysql，主库数据内容同步到从库中。

本次记录是在一台机器通过 mysqld_multi 操作一主两从数据库服务。若多台服务，则将配置文件拆分配置即可。

本次安装使用了 HomeBrew，若用其他方式，或者路径不一致，/opt/homebrew/opt/mysql 更改成自己的安装路径即可。

配置文件

brew install mysql

进入 mysql 安装之后的默认启动目录

cd /opt/homebrew/opt/mysql

创建数据目录 data，data 内创建三个文件夹，分别命名为 3306、3307和3308。

mkdir data
cd data
mkdir {3306,3307,3308}

3306、3307和3308 文件夹就是分别放置我们每个实例（mysql 服务器）中的所有数据库、数据表和一些日志文件的地方，每个文件夹可以看到一个 mysql 服务器。

在 mysql 包中新建一个文件，将文件命名为 my.cnf，从此以后，这个文件就是我们需要一直使用的配置文件。

touch my.cnf

打开 my.cnf 配置文件，将下列代码复制进入文件中：

[mysqld]
# mysql 安装目录
basedir=/opt/homebrew/opt/mysql

[mysqld_multi]
mysqld=/opt/homebrew/opt/mysql/bin/mysqld_safe
mysqladmin=/opt/homebrew/opt/mysql/bin/mysqladmin
log=/opt/homebrew/opt/mysql/data/mysql_multi.log

[mysqld3306]
mysqld=mysqld
mysqladmin=mysqladmin
# 数据库目录
datadir=/opt/homebrew/opt/mysql/data/3306/data
# 端口
port=3306
# socket 登录 mysqld_multi 启动自动生成 退出 自动删除
socket=/opt/homebrew/opt/mysql/mysql_3306.sock
server_id=1

[mysqld3307]
mysqld=mysqld
mysqladmin=mysqladmin
datadir=/opt/homebrew/opt/mysql/data/3307/data
port=3307
socket=/opt/homebrew/opt/mysql/mysql_3307.sock
server_id=2

[mysqld3308]
mysqld=mysqld
mysqladmin=mysqladmin
datadir=/opt/homebrew/opt/mysql/data/3308/data
port=3308
socket=/opt/homebrew/opt/mysql/mysql_3308.sock
server_id=3

安装实例

安装实例 3306

❯ mysqld --defaults-file=/opt/homebrew/etc/my.cnf --initialize --basedir=/opt/homebrew/opt/mysql/ --datadir=/opt/homebrew/opt/mysql/data/3306/data
2024-01-25T04:45:17.883145Z 0 [System] [MY-015017] [Server] MySQL Server Initialization - start.
2024-01-25T04:45:17.889196Z 0 [System] [MY-013169] [Server] /opt/homebrew/Cellar/mysql/8.2.0_1/bin/mysqld (mysqld 8.2.0) initializing of server in progress as process 60393
2024-01-25T04:45:17.895958Z 0 [Warning] [MY-010159] [Server] Setting lower_case_table_names=2 because file system for /opt/homebrew/opt/mysql/data/3306/data is case insensitive
2024-01-25T04:45:17.910343Z 1 [System] [MY-013576] [InnoDB] InnoDB initialization has started.
2024-01-25T04:45:18.038467Z 1 [System] [MY-013577] [InnoDB] InnoDB initialization has ended.
2024-01-25T04:45:18.632405Z 6 [Note] [MY-010454] [Server] A temporary password is generated for root@localhost: j.10weTJs)iu
2024-01-25T04:45:18.940457Z 0 [System] [MY-013172] [Server] Received SHUTDOWN from user <via user signal>. Shutting down mysqld (Version: 8.2.0).
2024-01-25T04:45:19.447294Z 0 [System] [MY-015018] [Server] MySQL Server Initialization - end.

记住 root 账户初始密码：j.10weTJs)iu

安装实例 3307

❯ mysqld --defaults-file=/opt/homebrew/etc/my.cnf --initialize --basedir=/opt/homebrew/opt/mysql/ --datadir=/opt/homebrew/opt/mysql/data/3307/data
2024-01-25T04:46:02.653813Z 0 [System] [MY-015017] [Server] MySQL Server Initialization - start.
2024-01-25T04:46:02.661065Z 0 [System] [MY-013169] [Server] /opt/homebrew/Cellar/mysql/8.2.0_1/bin/mysqld (mysqld 8.2.0) initializing of server in progress as process 62369
2024-01-25T04:46:02.667029Z 0 [Warning] [MY-010159] [Server] Setting lower_case_table_names=2 because file system for /opt/homebrew/opt/mysql/data/3307/data is case insensitive
2024-01-25T04:46:02.679468Z 1 [System] [MY-013576] [InnoDB] InnoDB initialization has started.
2024-01-25T04:46:02.771801Z 1 [System] [MY-013577] [InnoDB] InnoDB initialization has ended.
2024-01-25T04:46:03.385917Z 6 [Note] [MY-010454] [Server] A temporary password is generated for root@localhost: a#=MYe)L:8aj
2024-01-25T04:46:03.685023Z 0 [System] [MY-013172] [Server] Received SHUTDOWN from user <via user signal>. Shutting down mysqld (Version: 8.2.0).
2024-01-25T04:46:04.225769Z 0 [System] [MY-015018] [Server] MySQL Server Initialization - end.

记住 root 账户初始密码：a#=MYe)L:8aj

安装实例 3308

❯ mysqld --defaults-file=/opt/homebrew/etc/my.cnf --initialize --basedir=/opt/homebrew/opt/mysql/ --datadir=/opt/homebrew/opt/mysql/data/3308/data
2024-01-25T04:46:12.066014Z 0 [System] [MY-015017] [Server] MySQL Server Initialization - start.
2024-01-25T04:46:12.067626Z 0 [System] [MY-013169] [Server] /opt/homebrew/Cellar/mysql/8.2.0_1/bin/mysqld (mysqld 8.2.0) initializing of server in progress as process 62774
2024-01-25T04:46:12.069105Z 0 [Warning] [MY-010159] [Server] Setting lower_case_table_names=2 because file system for /opt/homebrew/opt/mysql/data/3308/data is case insensitive
2024-01-25T04:46:12.071151Z 1 [System] [MY-013576] [InnoDB] InnoDB initialization has started.
2024-01-25T04:46:12.171156Z 1 [System] [MY-013577] [InnoDB] InnoDB initialization has ended.
2024-01-25T04:46:12.598694Z 6 [Note] [MY-010454] [Server] A temporary password is generated for root@localhost: HJgqw!Bi6Efb
2024-01-25T04:46:12.866118Z 0 [System] [MY-013172] [Server] Received SHUTDOWN from user <via user signal>. Shutting down mysqld (Version: 8.2.0).
2024-01-25T04:46:13.501326Z 0 [System] [MY-015018] [Server] MySQL Server Initialization - end.

记住 root 账户初始密码：HJgqw!Bi6Efb

查看多实例

使用mysqld_multi命令查看这些MySQL服务是否开启

❯ mysqld_multi --defaults-extra-file=/opt/homebrew/opt/mysql/my.cnf report

Wide character in print at /opt/homebrew/bin/mysqld_multi line 684.
Reporting MySQL servers
MySQL server from group: mysqld3306 is not running
MySQL server from group: mysqld3307 is not running
MySQL server from group: mysqld3308 is not running

开启多实例

使用mysqld_multi命令开启实例

❯ mysqld_multi --defaults-extra-file=/opt/homebrew/opt/mysql/my.cnf start 3306,3307,3308

再次查看多实例

❯ mysqld_multi --defaults-extra-file=/opt/homebrew/opt/mysql/my.cnf report

Wide character in print at /opt/homebrew/bin/mysqld_multi line 684.
Reporting MySQL servers
MySQL server from group: mysqld3306 is running
MySQL server from group: mysqld3307 is running
MySQL server from group: mysqld3308 is running

查看 mysql 任务线程

❯ ps aux | grep mysqld

socket方式登录

使用 socket 的方式登录，必须使用 -S 参数，并且在后面加上.sock 文件的位置，需要注意的是，之后每一次登录，都需要使用这种 -S 方式进行登录

mysql -u root -p -S /opt/homebrew/opt/mysql/mysql_3306.sock

系统会提示输入密码，将上面记录的初始密码输入，进入 mysql 服务器

更改 root 的密码

为了方便，我们将 3306 端口的服务器密码设置为 3306。同样方式更改其他两个。

# 8.0 以下版本 密码模式 mysql_native_password
ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY '3306';
# 8.0 以上版本 密码模式 caching_sha2_password
ALTER USER 'root'@'localhost' IDENTIFIED WITH caching_sha2_password BY '3306';

关闭 mysql 服务器

mysqladmin -S /opt/homebrew/opt/mysql/mysql_3306.sock -uroot -p shutdown

日志文件

MySQL启动日志在哪？

启动动日志记录了MySQL启动时的状态，如果你启动失败可以查看该日志，可以使用最普通的文本编辑器打开，根据ERROR信息进行必要的调整。由于我们的配置文件my.cnf指定了生成路径，该日志在MySQL服务启动后自动生成在你的mysql包内，全称为mysqld_multi.log。

二进制文件在哪？

二进制文件主要记录MySQL数据库的变化，包含了所有更新了数据或者潜在更新了数据（例如没有匹配任何一行的UPDATE）的语句；还包含了每个更新数据库的语句的执行时间信息，使用二进制日志的目的是最大可能的恢复数据库，因为二进制日志包含备份后进行的所有更新，而且二进制文件是主从复制的重要桥梁和关键所在。

我们的二进制文件就在我们最初创建的3306文件夹内，具体路径是mysql/data/3306/data，使用 mysqlbinlog查看二进制文件。

每次重启服务器，都会新生成一个二进制日志，后缀以.000001开始递增。

其它日志文件在哪？

在配置文件中加上一行代码，就可以开启错误日志，当 mysql 需要记录错误发生时，就会保存在我们设置的路径上的日志中

log_error = /opt/homebrew/opt/mysql/data/3306/data/my_error.log

如果我们需要开启通用查询日志，可以在 mysql 中使用命令开启

mysql> set @@global.general_log = 1;
Query OK, 0 rows affected (0.01 sec)

执行成功之后，就会在 mysql/data/3306/data目录下新增一个.log 的日志文件

如果我们需要开启慢羊羊日志

mysql> set @@global.slow_query_log = 1;
Query OK, 0 rows affected (0.01 sec)

执行成功之后，就会在 mysql/data/3306/data目录下新增一个-slow.log 的日志文件

主从复制

配置文件

主库配置开启 binlog 参数

log_bin = mysql-bin

完整的 my.cnf 配置文件内容如下：

[mysqld]
basedir=/opt/homebrew/opt/mysql

[mysqld_multi]
mysqld=/opt/homebrew/opt/mysql/bin/mysqld_safe
mysqladmin=/opt/homebrew/opt/mysql/bin/mysqladmin
log=/opt/homebrew/opt/mysql/data/mysql_multi.log

[mysqld3306]
mysqld=mysqld
mysqladmin=mysqladmin
datadir=/opt/homebrew/opt/mysql/data/3306/data
port=3306
socket=/opt/homebrew/opt/mysql/mysql_3306.sock
server_id=1
log_error=/opt/homebrew/opt/mysql/data/3306/data/my_error.log
character-set-server=UTF8MB4

#设置二进制日志名称为mysql-bin
log_bin=mysql-bin
#需要主从复制的数据库 ，如多个则重复配置
binlog-do-db=boot
#复制过滤：也就是指定哪个数据库不用同步（mysql库一般不同步） ，如多个则重复配置
binlog-ignore-db=mysql
#主从复制的格式（mixed,statement,row，默认格式是statement。建议是设置为row，主从复制时数据更加能够统一）
binlog_format=row
#mysql8.0以上版本通过设置全局参数binlog_expire_logs_seconds修改binlog保存时间 以秒为单位；默认2592000 30天
binlog_expire_logs_seconds=604800


[mysqld3307]
mysqld=mysqld
mysqladmin=mysqladmin
datadir=/opt/homebrew/opt/mysql/data/3307/data
port=3307
socket=/opt/homebrew/opt/mysql/mysql_3307.sock
server_id=2
log_error=/opt/homebrew/opt/mysql/data/3306/data/my_error.log
character-set-server=UTF8MB4

#设置中继日志名称为slave-relay-bin
relay_log=slave-relay-bin
replicate-do-db=boot
binlog-ignore-db=mysql
binlog_format=row
read_only=ON
binlog_expire_logs_seconds=604800


[mysqld3308]
mysqld=mysqld
mysqladmin=mysqladmin
datadir=/opt/homebrew/opt/mysql/data/3308/data
port=3308
socket=/opt/homebrew/opt/mysql/mysql_3308.sock
server_id=3
log_error=/opt/homebrew/opt/mysql/data/3306/data/my_error.log
character-set-server=UTF8MB4

#设置中继日志名称为slave-relay-bin
relay_log=slave-relay-bin
replicate-do-db=boot
binlog-ignore-db=mysql
binlog_format=row
read_only=ON
binlog_expire_logs_seconds=604800

设置完成并保存后记得重启服务。

同步账号

主库操作

主库创建从库同步账号

mysql> CREATE USER 'replication'@'%' IDENTIFIED BY '123456';

赋予 REPLICATION 账号 salve 权限

mysql> GRANT REPLICATION SLAVE ON *.* TO 'replication'@'%';

刷新

mysql> FLUSH PRIVILEGES;

查看主库状态

mysql> show master status\G
*************************** 1. row ***************************
             File: mysql-bin.000008
         Position: 575
     Binlog_Do_DB: boot
 Binlog_Ignore_DB: mysql
Executed_Gtid_Set:
1 row in set, 1 warning (0.00 sec)

从库操作

设定从主库同步

change master to
    MASTER_HOST='localhost',
    MASTER_PORT=3306,
    MASTER_USER='replication',
    MASTER_PASSWORD='123456',
    MASTER_LOG_FILE='mysql-bin.000008',
    MASTER_LOG_POS=575,
    GET_MASTER_PUBLIC_KEY=1;

从库同步开关

mysql> stop slave;
mysql> start slave;

查看从库状态

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for source to send event
                  Master_Host: localhost
                  Master_User: replication
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000008
          Read_Master_Log_Pos: 575
               Relay_Log_File: slave-relay-bin.000002
                Relay_Log_Pos: 744
        Relay_Master_Log_File: mysql-bin.000008
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: boot

总结

此文仅记录使用 mysqld_multi ，正式环境还是以实际方案为准。