目录
1. 主从简介
在现代企业中，数据显得尤为重要，而存储数据的数据库选择又五花八门，但无论是何种数据库，均存在着一种隐患。
想几个问题：
用一台数据库存放数据，若此数据库服务器宕机了导致数据丢失怎么办？
业务量大了，数据多了，访问的人多了，一台数据库无法保证服务质量了怎么办？
1.1 主从作用
实时灾备，用于故障切换
读写分离，提供查询服务
备份，避免影响业务
1.2 主从形式
一主一从
主主复制
一主多从---扩展系统读取的性能，因为读是在从库读取的
多主一从---5.7开始支持
联级复制
2. 主从复制原理
主从复制步骤：
主库将所有的写操作记录到binlog日志中并生成一个log dump线程，将binlog日志传给从库的I/O线程
从库生成两个线程，一个I/O线程，一个SQL线程
I/O线程去请求主库的binlog，并将得到的binlog日志写到relay log（中继日志） 文件中
SQL线程，会读取relay log文件中的日志，并解析成具体操作，来实现主从的操作一致，达到最终数据一致的目的
3. 主从复制配置
3.1主从复制配置步骤：
确保从数据库与主数据库里的数据一样
在主数据库里创建一个同步账号授权给从数据库使用
配置主数据库（修改配置文件）
配置从数据库（修改配置文件）
需求：
搭建两台MySQL服务器，一台作为主服务器，一台作为从服务器，主服务器进行写操作，从服务器进行读操作
3.2 mysql主从配置
3.2.1 确保从数据库与主数据库里的数据一样
为确保从数据库与主数据库里的数据一样，先全备主数据库并还原到从数据库中
//先查看主库有哪些库
[root@localhost ~]# mysql -uroot -p123456 -e 'show databases;'
mysql: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
//再查看从库有哪些库
[root@localhost ~]# mysql -uroot -p123456 -e 'show databases;'
mysql: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
//全备主库
//全备主库时需要另开一个终端，给数据库加上读锁，避免在备份期间有其他人在写入导致数据不一致
mysql> FLUSH TABLES WITH READ LOCK;
Query OK, 0 rows affected (0.14 sec)
//此锁表的终端必须在备份完成以后才能退出
//备份主库并将备份文件传送到从库
[root@localhost ~]# mysqldump -uroot -p123456 --all-databases > /opt/all-20191224.sql
mysqldump: [Warning] Using a password on the command line interface can be insecure.
[root@localhost ~]# ls /opt/
all-20191224.sql data
[root@localhost ~]# scp /opt/all-20191224.sql root@192.168.136.145:/opt/
root@192.168.136.145's password:
all-20191224.sql 100% 782KB 2.7MB/s 00:00
//解除主库的锁表状态，直接退出交互式界面即可
mysql> quit
Bye
//在从库上恢复主库的备份并查看从库有哪些库，确保与主库一致
[root@localhost ~]# mysql -uroot -p123456 < /opt/all-20191224.sql
mysql: [Warning] Using a password on the command line interface can be insecure.
[root@localhost ~]# mysql -uroot -p123456 -e 'show databases;'
mysql: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
3.2.2 在主数据库里创建一个同步账号授权给从数据库使用
mysql> CREATE USER 'repl'@'192.168.136.145' IDENTIFIED BY '123456';
Query OK, 0 rows affected (0.03 sec)
mysql> GRANT REPLICATION SLAVE ON *.* TO 'repl'@'192.168.136.145';
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
3.2.3 配置主数据库
[root@localhost ~]# vim /etc/my.cnf
[mysqld]
basedir = /usr/local/mysql
datadir = /opt/data
socket = /tmp/mysql.sock
port = 3306
pid-file = /opt/data/mysql.pid
user = mysql
skip-name-resolve
log-bin=mysql-bin
server-id=1
//重启mysql服务
[root@localhost ~]# vim /etc/my.cnf
[root@localhost ~]# service mysqld restart
Shutting down MySQL.. SUCCESS!
Starting MySQL.... SUCCESS!
[root@localhost ~]# ss -antl
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 0 128 *:22 *:*
LISTEN 0 100 127.0.0.1:25 *:*
LISTEN 0 128 :::22 :::*
LISTEN 0 100 ::1:25 :::*
LISTEN 0 80 :::3306 :::*
//查看主库的状态
mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000001 | 154 | | | |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
3.2.4 配置从数据库
[root@localhost ~]# vim /etc/my.cnf
[mysqld]
basedir = /usr/local/mysql
datadir = /opt/data
socket = /tmp/mysql.sock
port = 3306
pid-file = /opt/data/mysql.pid
user = mysql
skip-name-resolve
server-id=2
relay-log=mysql-relay-bin
//重启从库的mysql服务
[root@localhost ~]# vim /etc/my.cnf
[root@localhost ~]# service mysqld restart
Shutting down MySQL.. SUCCESS!
Starting MySQL........................... SUCCESS!
[root@localhost ~]# ss -antl
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 0 128 *:22 *:*
LISTEN 0 100 127.0.0.1:25 *:*
LISTEN 0 128 *:10050 *:*
LISTEN 0 25 *:514 *:*
LISTEN 0 128 :::22 :::*
LISTEN 0 100 ::1:25 :::*
LISTEN 0 25 :::514 :::*
LISTEN 0 80 :::3306 :::*
//配置并启动主从复制
mysql> CHANGE MASTER TO
-> MASTER_HOST='192.168.136.144',
-> MASTER_USER='repl',
-> MASTER_PASSWORD='123456',
-> MASTER_LOG_FILE='mysql-bin.000001',
-> MASTER_LOG_POS=154;
Query OK, 0 rows affected, 2 warnings (0.05 sec)
mysql> start slave;
Query OK, 0 rows affected (0.04 sec)
//查看从服务器状态
mysql> show slave status G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.136.144
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000001
Read_Master_Log_Pos: 154
Relay_Log_File: mysql-relay-bin.000002
Relay_Log_Pos: 320
Relay_Master_Log_File: mysql-bin.000001
Slave_IO_Running: Yes //此处必须为Yes
Slave_SQL_Running: Yes //此处必须为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: 154
Relay_Log_Space: 527
Until_Condition: None
Until_Log_File:
3.2.5 测试验证
在主服务器的student库的student表中插入数据：
mysql> create database student;
Query OK, 1 row affected (0.03 sec)
mysql> use student;
Database changed
mysql> create table student (id int not null,name varchar(100) not null,age tinyint);
Query OK, 0 rows affected (0.09 sec)
mysql> insert into student (id,name,age) value (1,'tom',20);
Query OK, 1 row affected (0.16 sec)
mysql> select * from student;
+----+------+------+
| id | name | age |
+----+------+------+
| 1 | tom | 20 |
+----+------+------+
1 row in set (0.00 sec)
在从数据库中查看数据是否同步：
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| student |
| sys |
+--------------------+
5 rows in set (0.00 sec)
mysql> use student;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> show tables;
+-------------------+
| Tables_in_student |
+-------------------+
| student |
+-------------------+
1 row in set (0.00 sec)
mysql> select * from student;
+----+------+------+
| id | name | age |
+----+------+------+
| 1 | tom | 20 |
+----+------+------+
1 row in set (0.00 sec)