mysql基础之mariadb集群双主（主主）架构

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 statusG;
*************************** 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 statusG;
*************************** 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)