一、概念

在企业中，数据库高可用一直是企业的重中之重，中小企业很多都是使用mysql主从方案，一主多从，读写分离等，但是单主存在单点故障，从库切换成主库需要作改动。因此，如果是双主或者多主，就会增加mysql入口，增加高可用。不过多主需要考虑自增长ID问题，这个需要特别设置配置文件，比如双主，可以使用奇偶，总之，主之间设置自增长ID相互不冲突就能完美解决自增长ID冲突问题。

单点故障解决方案：

主主架构：

互为主备，互相监控对方二进制日志文件进行同步

note：当两个sql语句发生冲突的时候主主架构有可能出现数据不一致的现象；

MHA(master high availability)：

HMA可以有多个配置文件，一个配置文件监控一个主从架构

二、主主架构思路

1、两台mysql都可读可写，互为主备，默认只使用一台(masterA)负责数据的写入，另一台(masterB)备用；

2、masterA是masterB的主库，masterB又是masterA的主库，它们互为主从；

3、两台主库之间做高可用，可以采用keepalived等方案(使用VIP对外提供服务)；

4、所有提供服务的从服务器与masterB进行主从同步(双主多从);

5、建议采用高可用策略的时候，masterA或masterB均不因宕机恢复后而抢占VIP(非抢占模式)；

三、演示步骤

环境(主1服务器端IP：192.168.11.7；主2服务器端IP：192.168.11.8)

1、修改配置文件，配置服务器编号，开启bin-log

[root@bi7 ~]# vim /etc/my.cnf.d/server.cnf

[mysqld]

datadir=/var/lib/mysql

socket=/var/lib/mysql/mysql.sock

server-id=7

log_bin=mysql-bin

binlog_format=row

relay-log=relay-mysql

relay-log-index=relay-mysql.index

log_slave_updates=on

auto-increment-increment=2

auto-increment-offset=1

[root@bi8 ~]# vim /etc/my.cnf.d/server.cnf

[mysqld]

datadir=/var/lib/mysql

socket=/var/lib/mysql/mysql.sock

server-id=8

log_bin=mysql-bin

binlog_format=row

relay-log=relay-mysql

relay-log-index=relay-mysql.index

log_slave_updates=on

auto-increment-increment=2

auto-increment-offset=2

2、重启mysql服务(两台主机)

systemctl restart mariadb

ss -tnl |grep 3306

LISTEN     0      80          :::3306                    :::*

3、创建复制用的用户(两台主机)

[root@bi8 ~]# mysql -uroot -proot

Welcome to the MariaDB monitor. Commands end with ; or \g.

Your MariaDB connection id is 9

Server version: 10.2.26-MariaDB-log MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the curbit input statement.

MariaDB [(none)]> grant replication slave on *.* to 'master'@'%' identified by '123';

Query OK, 0 rows affected (0.00 sec)

4、(若第一次同步可忽略此步骤)这里可以清空两台主机的master和slave日志(若之前有开启过同步的，需要先停止同步：stop slave;)

在mysql命令行中输入：

reset master;

reset slave;

5、查看二进制日志文件的位置

--主1

MariaDB [(none)]> show master status;

+------------------+----------+--------------+------------------+

| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |

+------------------+----------+--------------+------------------+

| mysql-bin.000001 | 1087 | | |

+------------------+----------+--------------+------------------+

1 row in set (0.00 sec)

--主2

MariaDB [(none)]> show master status;

+------------------+----------+--------------+------------------+

| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |

+------------------+----------+--------------+------------------+

| mysql-bin.000001 | 520 | | |

+------------------+----------+--------------+------------------+

1 row in set (0.00 sec)

6、为防止配置同步的同时又数据写入，可给数据库加读锁(两台主机)：

MariaDB [(none)]> flush tables with read lock;

Query OK, 0 rows affected (0.00 sec)

7、两台服务器互相连接

--主1连接主2

MariaDB [(none)]> change master to master_host='192.168.11.8',master_user='master',master_password='123',master_log_file='mysql-bin.000001',master_log_pos=520;

Query OK, 0 rows affected (0.01 sec)

--主2连接主1

MariaDB [(none)]> change master to master_host='192.168.11.7',master_user='master',master_password='123',master_log_file='mysql-bin.000001',master_log_pos=1087;

Query OK, 0 rows affected (0.05 sec)

8、启动slave(两台主机)

MariaDB [(none)]> start slave;

Query OK, 0 rows affected (0.01 sec)

9、检查连接状态(两台主机)

MariaDB [(none)]> show slave status\G;

*************************** 1. row ***************************

Slave_IO_State: Connecting to master

Master_Host: 192.168.11.7

Master_User: master

Master_Port: 3306

Connect_Retry: 60

Master_Log_File: mysql-bin.000001

Read_Master_Log_Pos: 1087

Relay_Log_File: relay-mysql.000001

Relay_Log_Pos: 4

Relay_Master_Log_File: mysql-bin.000001

Slave_IO_Running: Connecting

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: 1087

Relay_Log_Space: 256

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: NULL

Master_SSL_Verify_Server_Cert: No

Last_IO_Errno: 2003

Last_IO_Error: error connecting to master 'master@192.168.11.7:3306' - retry-time: 60 maximum-retries: 86400 message: Can't connect to MySQL server on '192.168.11.7' (113 "No route to host")

Last_SQL_Errno: 0

Last_SQL_Error:

Replicate_Ignore_Server_Ids:

Master_Server_Id: 0

Master_SSL_Crl:

Master_SSL_Crlpath:

Using_Gtid: No

Gtid_IO_Pos:

Replicate_Do_Domain_Ids:

Replicate_Ignore_Domain_Ids:

Parallel_Mode: conservative

SQL_Delay: 0

SQL_Remaining_Delay: NULL

Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it

1 row in set (0.00 sec)

10、添加防火墙规则

[root@bi7 ~]# firewall-cmd --add-port=3306/tcp

success

[root@bi7 ~]# firewall-cmd --add-port=3306/tcp --permanent

success

[root@bi8 ~]# firewall-cmd --add-port=3306/tcp

success

[root@bi8 ~]# firewall-cmd --add-port=3306/tcp --permanent

success

11、再次检查连接状态(两台主机)

MariaDB [(none)]> show slave status\G;

*************************** 1. row ***************************

Slave_IO_State: Waiting for master to send event

Master_Host: 192.168.11.8

Master_User: master

Master_Port: 3306

Connect_Retry: 60

Master_Log_File: mysql-bin.000001

Read_Master_Log_Pos: 520

Relay_Log_File: relay-mysql.000002

Relay_Log_Pos: 555

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:

Replicate_Wild_Ignore_Table:

Last_Errno: 0

Last_Error:

Skip_Counter: 0

Exec_Master_Log_Pos: 520

Relay_Log_Space: 860

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: 8

Master_SSL_Crl:

Master_SSL_Crlpath:

Using_Gtid: No

Gtid_IO_Pos:

Replicate_Do_Domain_Ids:

Replicate_Ignore_Domain_Ids:

Parallel_Mode: conservative

SQL_Delay: 0

SQL_Remaining_Delay: NULL

Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it

1 row in set (0.00 sec)

12、测试

--解锁(两台主机)

MariaDB [(none)]> unlock tables;

Query OK, 0 rows affected (0.00 sec)

--查看主1的原本数据库

MariaDB [(none)]> show databases;

+--------------------+

| Database |

+--------------------+

| information_schema |

| mysql |

| performance_schema |

| bi |

+--------------------+

4 rows in set (0.00 sec)

--在主1上创建新库yang

MariaDB [(none)]> create database if not exists yang default character set utf8;

Query OK, 1 row affected (0.00 sec)

--查看主2是否有新建的数据库

MariaDB [(none)]> show databases;

+--------------------+

| Database |

+--------------------+

| information_schema |

| mysql |

| performance_schema |

| yang |

+--------------------+

4 rows in set (0.10 sec)

--使用yang数据库

MariaDB [(none)]> use yang;

Database changed

--在主2上创建新表hello，并插入一条数据

MariaDB [yang]> create table hello(id tinyint unsigned primary key auto_increment not null,name varchar(20));

Query OK, 0 rows affected (0.03 sec)

MariaDB [yang]> insert into hello values(0,'李国祥');

Query OK, 1 row affected (0.00 sec)

MariaDB [yang]> select * from hello;

+----+-----------+

| id | name |

+----+-----------+

| 2 | 李国祥 |

+----+-----------+

1 row in set (0.00 sec)

--查看主1是否新插入的数据

MariaDB [(none)]> use yang;

Database changed

MariaDB [yang]> select * from hello;

+----+-----------+

| id | name |

+----+-----------+

| 2 | 李国祥 |

+----+-----------+

1 row in set (0.01 sec)