Mariadb简单(主从)复制、

实验环境：centos7.3

centos7自带的mariadb，yum安装

[root@centos7 ~]# rpm -qa mariadb
mariadb-5.5.52-1.el7.x86_64
[root@centos7 ~]# uname -r
3.10.0-514.el7.x86_64

ip 地址：

master：192.168.23.148

slave：192.168.23.149

一.主从复制

主从复制，是用来建立一个和主数据库完全一样的数据库环境，称为从数据库；主数据库一般是实时的业务数据库，从数据库的作用和使用场合一般有几个：

一是作为后备数据库，主数据库服务器故障后，可切换到从数据库继续工作；

二是可在从数据库作备份、数据统计等工作，这样不影响主数据库的性能；

数据分布：能够将数据分散到多个位置，可以实现异地灾备

负载均衡：读操作，适用于读密集型的应用

备份：备份的时候可以停止从节点进行备份，备份更安全

高可用和故障切换：主节点故障，可以将从节点提升为主节点（需要手动实现，或者脚本监控实现，不如corosync或者heartbeat之类高可用方案）

主从原理图：



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；

主库会生成一个 log dump 线程，用来给从库 i/o线程传binlog；

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，而最终数据一致；

1.主从节点的配置

1.1 master节点的配置：

（1）启动二进制日志log-bin

（2）以及唯一的 server-id

[root@centos7 ~]# vim /etc/my.cnf.d/server.cnf

#
# These groups are read by MariaDB server.
# Use it for options that only the server (but not clients)

should see
#
# See the examples of server my.cnf files in

/usr/share/mysql/
#

# this is read by the standalone daemon and embedded servers
[server]

# this is only for the mysqld standalone daemon
[mysqld]
server_id = 1
log_bin = master-bin
skip_name_resolve = ON
当然如果使用绝对路径如：、/mydata/data
必须所属组和所属都必须是mysql，如果不是用chown -R mysql.mysql /mydata/data  修改

完成后重启服务：查看文件

[root@centos7 ~]# systemctl restart mariadb.service
[root@centos7 ~]# cd /var/lib/mysql/
[root@centos7 mysql]# ls
master-bin.000001  master-bin.000002 master-bin.index

创建一个有复制权限的账号：（REPLICATION SLAVE,REPLICATION CLIENT）

MariaDB [mysql]> GRANT REPLICATION SLAVE,REPLICATION CLIENT ON *.* TO 'repluser'@'192.168.%.%' IDENTIFIED BY 'replpass';
Query OK, 0 rows affected (0.09 sec)

MariaDB [mysql]> FLUSH PRIVILEGES; #刷新，生效
Query OK, 0 rows affected (0.00 sec)

1.2 从节点的配置：

[root@cento7 ~]# vim /etc/my.cnf.d/server.cnf

#
# These groups are read by MariaDB server.
# Use it for options that only the server (but not clients) should see
#
# See the examples of server my.cnf files in /usr/share/mysql/
#

# this is read by the standalone daemon and embedded servers
[server]
# this is only for the mysqld standalone daemon
[mysqld]
server_id= 2
relay_log= relay-log #开启中继日志
read_only= ON #开启只读 关闭从服务器的写入功能

先查看一下主服务器的二进制日志位置，确定从服务器的那个位置复制

MariaDB [mysql]> show master status;
+-------------------+----------+--------------+------------------+
| File              | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+-------------------+----------+--------------+------------------+
| master-bin.000002 |      507 |              |                  |
+-------------------+----------+--------------+------------------+
1 row in set (0.00 sec)

启动服务：从服务器使用CHANGE MASTER连接主服务器进行复制

MariaDB [mysql]> change master to master_host='192.168.23.148', master_user='repluser', master_password='replpass', master_log_file='master-bin.000002', master_log_pos=507;
Query OK, 0 rows affected (0.05 sec)

查看IO线程与SQL线程

MariaDB [(none)]> show slave status\G
*************************** 1. row ***************************
Slave_IO_State:
Master_Host: 192.168.23.148
Master_User: repluser
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: master-bin.000002
Read_Master_Log_Pos: 507
Relay_Log_File: relay-log.000001
Relay_Log_Pos: 4
Relay_Master_Log_File: master-bin.000002
Slave_IO_Running: No  #未启动
Slave_SQL_Running: No  #未启动
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: 507
Relay_Log_Space: 245
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: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 0
1 row in set (0.00 sec)

手动开启slave 并查看状态：

MariaDB [(none)]> start slave;
Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.23.148
Master_User: repluser
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: master-bin.000002
Read_Master_Log_Pos: 850
Relay_Log_File: relay-log.000002
Relay_Log_Pos: 873
Relay_Master_Log_File: master-bin.000002
Slave_IO_Running: Yes #yes 表示开启
Slave_SQL_Running: Yes
Replicate_Do_DB:

查看中继日志：

[root@cento7 ~]# cd /var/lib/mysql/
[root@cento7 mysql]# ls
aria_log.00000001  binlog.index  ib_logfile0                relay-log.000001
aria_log_control          ib_logfile1         relay-log.index
binlog.000001      ibdata1       master.info  performance_schema  relay-log.info

验证主从复制：

在主节点上创建一个数据库;

MariaDB [mysql]> create database tb1;
Query OK, 1 row affected (0.03 sec)

MariaDB [mysql]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| han                |
| mydb               |
| mysql              |
| performance_schema |
| tb1                |
| test               |
| wordpress          |
+--------------------+

从服务器上查看：

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| blog               |
| mysql              |
| performance_schema |
| tb1                |
| test               |
+--------------------+

在查看一下从服务器的状态日志的记录已经发生了改变

MariaDB [(none)]> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.23.148
Master_User: repluser
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: master-bin.000002
Read_Master_Log_Pos: 850
Relay_Log_File: relay-log.000002
Relay_Log_Pos: 873
Relay_Master_Log_File: master-bin.000002
Slave_IO_Running: Yes
Slave_SQL_Running: Yes