MySQL 主从同步复制实现步骤技术
MySQL 主从复制手把手教程，本文以最精简的命令实现整个过程，不折腾，不冗长，真材实料。
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主从复制最好遵守从服务器的版本不低于主服务器的版本原则，MariaDB 和 MySQL 之间也许会有一些问题（笔者测试过能正常复制）。整个过程遇到各种问题在所难免，本文基于安全的缘故，增加了 ssl 的步骤。
先配置服务器
主：
[mysqld] server-id=2 log-bin=mysql-bin innodb_flush_log_at_trx_commit=1 sync_binlog=1 ssl ssl-ca=/var/lib/mysql/certs/ca-cert.pem ssl-cert=/var/lib/mysql/certs/server-cert.pem ssl-key=/var/lib/mysql/certs/server-key.pem bind-address = 0.0.0.0
从
[mysqld] server-id=3 replicate_wild_do_table=lmlphp.% replicate_wild_do_table=db_prefix%.%
创建证书
在 /var/lib/mysql 下 创建文件夹 certs，这里需要注意的是 MySQL 生成证书输入的所有信息都必须一致，MariaDB 和 MySQL 不同的是输入的用户信息服务端和客户端不能一致。如下：
openssl genrsa 2048 > ca-key.pem openssl req -new -x509 -nodes -days 3600 -key ca-key.pem -out ca-cert.pem openssl req -newkey rsa:2048 -days 3600 -nodes -keyout server-key.pem -out server-req.pem openssl rsa -in server-key.pem -out server-key.pem openssl x509 -req -in server-req.pem -days 3600 -CA ca-cert.pem -CAkey ca-key.pem -set_serial 01 -out server-cert.pem openssl req -newkey rsa:2048 -days 3600 -nodes -keyout client-key.pem -out client-req.pem openssl rsa -in client-key.pem -out client-key.pem openssl x509 -req -in client-req.pem -days 3600 -CA ca-cert.pem -CAkey ca-key.pem -set_serial 01 -out client-cert.pem chown -R mysql.mysql /var/lib/mysql/certs
复制证书到从服务器
把 ca-cert.pem，client-cert.pem，client-key.pem 复制到从服务器上的 /var/log/mysql/certs/repl 下
scp -p master:/var/lib/mysql/certs/* slave:/var/lib/mysql/certs/repl/
在主服务器上创建复制账户
CREATE USER 'repl_all'@'%' IDENTIFIED BY '123456'; GRANT REPLICATION SLAVE ON *.* TO 'repl_all'@'%' require ssl; FLUSH PRIVILEGES;
重启服务
在主从服务器分别执行（mysql 这点做的很不好，必须重启才能生效）
service mysql restart
创建备份数据
推荐使用 mysqldump 生成
mysqldump --all-databases --default-character-set=utf8mb4 --master-data > dump.db // or mysqldump --databases db1 db2 --default-character-set=utf8mb4 --master-data > dump.db
使用 vim 或者 head 查看主服务信息
head -n 100 dump.db | less
将数据传给从服务器
将 dump.db 传给从服务器，然后导入到 mysql 中，使用 source 导入
source dump.db
CHANGE MASTER TO
在从服务器上执行，修改成对应 IP，密码，文件，位置
change master to master_host='119.119.119.119', master_user='repl_all', master_password='123456', master_log_file='mysql-bin.000001', master_log_pos=312065, master_ssl=1, master_ssl_ca='/var/lib/mysql/certs/repl/ca-cert.pem', master_ssl_cert='/var/lib/mysql/certs/repl/client-cert.pem',master_ssl_key='/var/lib/mysql/certs/repl/client-key.pem';
启动复制
在从库上执行
start slave
查看状态
到此，同步工作已经完成。查看从服务器：
MariaDB > show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 119.119.119.119
Master_User: repl_all
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000001
Read_Master_Log_Pos: 550149
Relay_Log_File: mysqld-relay-bin.000002
Relay_Log_Pos: 215940
Relay_Master_Log_File: mysql-bin.000001
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table: lmlphp.%,db_prefix%.%
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 550149
Relay_Log_Space: 216239
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: Yes
Master_SSL_CA_File: /var/lib/mysql/certs/repl/ca-cert.pem
Master_SSL_CA_Path:
Master_SSL_Cert: /var/lib/mysql/certs/repl/client-cert.pem
Master_SSL_Cipher:
Master_SSL_Key: /var/lib/mysql/certs/repl/client-key.pem
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: 2
Master_SSL_Crl: /var/lib/mysql/certs/repl/ca-cert.pem
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)
MariaDB > show processlist;
+----+-------------+-----------+----------------+---------+------+-----------------------------------------------------------------------------+------------------+----------+
| Id | User | Host | db | Command | Time | State | Info | Progress |
+----+-------------+-----------+----------------+---------+------+-----------------------------------------------------------------------------+------------------+----------+
| 2 | root | localhost | lmlphp | Query | 0 | init | show processlist | 0.000 |
| 3 | system user | | NULL | Connect | 167 | Waiting for master to send event | NULL | 0.000 |
| 4 | system user | | NULL | Connect | 4 | Slave has read all relay log; waiting for the slave I/O thread to update it | NULL | 0.000 |
+----+-------------+-----------+----------------+---------+------+-----------------------------------------------------------------------------+------------------+----------+
3 rows in set (0.00 sec)
查看主服务器
mysql> show master status; +------------------+----------+--------------+------------------+-------------------+ | File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set | +------------------+----------+--------------+------------------+-------------------+ | mysql-bin.000001 | 575885 | | | | +------------------+----------+--------------+------------------+-------------------+ 1 row in set (0.00 sec) mysql> show processlist; +-----+----------+------------------------------------+--------+-------------+------+---------------------------------------------------------------+------------------+ | Id | User | Host | db | Command | Time | State | Info | +-----+----------+------------------------------------+--------+-------------+------+---------------------------------------------------------------+------------------+ | 2 | root | localhost | lmlphp | Query | 0 | starting | show processlist | | 664 | repl_all | 119.119.119.119:34330 | NULL | Binlog Dump | 194 | Master has sent all binlog to slave; waiting for more updates | NULL | +-----+----------+------------------------------------+--------+-------------+------+---------------------------------------------------------------+------------------+ 2 rows in set (0.00 sec)
半同步复制 semi
半同步复制是 Google 开发的 MySQL 插件，笔者认为，半同步复制应用场景不多，并不适合中小企业。半同步复制必须等待至少一个从服务器同步完成才提交事务，这种机制在大多数情况下是不适用的。有些问题，可以从应用层面乃至业务层面去避免。
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