mysql主从模式：
主从复制：
从服务器：
I/O线程：从master请求二进制日志信息，并保存至中继日志；
SQL线程：从relay log中读取日志信息，在本地完成重放；
配置过程：
1、master
(1) 启用二进制日志；
(2) 设置一个在当前集群中惟一的server-id；
(3) 创建一个有复制权限(REPLICATION SLAVE, REPLICATION CLIENT)账号；
2、slave
(1) 启用中继日志；
(2) 设置一个在当前集群中惟一的server-id；
(3) 使用有复制权限用户账号连接至主服务器，并启动复制线程；
示例：
环境为CentOS7.2,mariadb-server-5.5.52-1.el7.x86_64
主服务器：
[root@node3 /]# vim /etc/my.cnf
log-bin=master-bin###启用二进制日志
server-id=1###设置server-id
skip_name_resolve = ON
innodb_file_per_table = ON
[root@node3 /]# systemctl start mariadb.service###启动服务
MariaDB [(none)]> SHOW GLOBAL VARIABLES LIKE '%log%';###进入mysql查看配置
log_bin | ON
MariaDB [(none)]> SHOW MASTER LOGS;
+-------------------+-----------+
| Log_name | File_size |
+-------------------+-----------+
| master-bin.000001 | 264 |
| master-bin.000002 | 245 |
MariaDB [(none)]> SHOW GLOBAL VARIABLES LIKE '%server%';###查看server-id
+----------------------+-------------------+
| Variable_name | Value |
+----------------------+-------------------+
| character_set_server | latin1 |
| collation_server | latin1_swedish_ci |
| server_id | 1 |
+----------------------+-----------------
MariaDB [(none)]> GRANT REPLICATION SLAVE,REPLICATION CLIENT ON *.* TO 'repluser'@'192.168
.%.%' IDENTIFIED BY 'replpass';Query OK, 0 rows affected (0.05 sec)
###创建一个有复制权限(REPLICATION SLAVE, REPLICATION CLIENT)账号
MariaDB [(none)]> FLUSH PRIVILEGES;###主服务器配置完成
Query OK, 0 rows affected (0.00 sec)
从服务器：
[root@localhost ~]# vim /etc/my.cnf
skip_name_resolve=ON
innodb_file_per_table=ON
relay-log=relay-log###启用中继日志
relay-log-index=relay-log.index ###设置中继日志索引文件名
server-id=2 ###设置server-id
[root@localhost ~]# systemctl start mariadb.service
MariaDB [(none)]> SHOW GLOBAL VARIABLES LIKE '%log%';###查看中继日志
| relay_log | relay-log
relay_log_index | relay-log.index
MariaDB [(none)]> SHOW GLOBAL VARIABLES LIKE '%server%';
+----------------------+-------------------+
| Variable_name | Value |
+----------------------+-------------------+
| character_set_server | latin1 |
| collation_server | latin1_swedish_ci |
| server_id | 2 |###查看server-id
###查看主服务器节点的位置
MariaDBMariaDB [(none)]> SHOW MASTER LOGS;
+-------------------+-----------+
| Log_name | File_size |
+-------------------+-----------+
| master-bin.000001 | 264 |
| master-bin.000002 | 264 |
| master-bin.000003 | 498 |
+-------------------+-----------+###位置为498
MariaDB [(none)]> CHANGE MASTER TO MASTER_HOST='192.168.0.188', MASTER_USER='repluser', MA
STER_PASSWORD='replpass',MASTER_LOG_FILE='master-bin.000003',MASTER_LOG_POS=498;Query OK, 0 rows affected (0.05 sec) ###指向主节点服务器
MariaDB [(none)]> START SLAVE; ###启动复制线程
Query OK, 0 rows affected (0.03 sec)
MariaDB [(none)]> SHOW SLAVE STATUS\G###查看从服务器信息
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.0.188
Master_User: repluser
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: master-bin.000003
Read_Master_Log_Pos: 498
Relay_Log_File: relay-log.000002
Relay_Log_Pos: 530
Relay_Master_Log_File: master-bin.000003
Slave_IO_Running: Yes###IO线程启动
Slave_SQL_Running: Yes###SQL线程启动
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: 498
Relay_Log_Space: 818
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: 1
1 row in set (0.00 sec)
###从服务器配置完成
测试：
从节点不能写，只有主节点可写：
主节点：
MariaDB [(none)]> CREATE DATABASE mydb;###主节点创建一个库
Query OK, 1 row affected (0.00 sec)
MariaDB [(none)]> SHOW MASTER LOGS;
+-------------------+-----------+
| Log_name | File_size |
+-------------------+-----------+
| master-bin.000001 | 264 |
| master-bin.000002 | 264 |
| master-bin.000003 | 581 |###查看二进制日志位置在581
在从节点查看：
MariaDB [(none)]> SHOW SLAVE STATUS\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.0.188
Master_User: repluser
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: master-bin.000003
Read_Master_Log_Pos: 581###位置为581
Relay_Log_File: relay-log.000002
Relay_Log_Pos: 530
Relay_Master_Log_File: master-bin.000003
Slave_IO_Running: Yes
Slave_SQL_Running: No
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 1007
Last_Error: Error 'Can't create database 'mydb'; database exists' on qu
ery. Default database: 'mydb'. Query: 'CREATE DATABASE mydb' Skip_Counter: 0
Exec_Master_Log_Pos: 498
Relay_Log_Space: 901
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: 1007
Last_SQL_Error: Error 'Can't create database 'mydb'; database exists' on qu
ery. Default database: 'mydb'. Query: 'CREATE DATABASE mydb' Replicate_Ignore_Server_Ids:
Master_Server_Id: 1
1 row in set (0.00 sec)
MariaDB [(none)]> SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| hellodb |
| mydb |###显示mydb同步到从节点
| mysql |
| performance_schema |
| test |
+--------------------+
6 rows in set (0.00 sec)
另外：复制架构中应该注意的问题：
1.限制从服务器为只读
在从服务器上设置read_only=ON,此限制对拥有SUPER权限的用户均无效
阻止所有用户：
mysql> FLUSH TABLES WITH READ LOCK; ###启动一个连接线程后不退出终端，所有写操作被阻塞，只能读操作。
2.保证主从复制的事务安全
在master节点启用参数：
sync_binlog=ON
###事务提交时，将binlog缓冲区的事件立即同步至磁盘中二进制日志文件中。
如果用到的为InnoDB存储引擎：
innodb_flush_logs_at_trx_commit=ON ###事务提交时立即将缓冲区与事务相关的数据刷写至事务日志中
innodb_support_xa=ON###分布式事务
在slave节点：
skip_slave_start=ON ###从节点开机不自动启动复制线程（检测无误后手动启动）
mster节点：
sync_master_info###同步master_info信息至磁盘
slave节点：
sync_relay_log###同步relay_log信息至磁盘
sync_relay_log_info
如果主节点已经运行一段时间，且有大量数据时，配置slave节点：
通过备份恢复数据至从服务器
复制起始位置为备份时二进制日志文件及其POS。