MySQL Replication

一般来说，应用系统性能扩展不外乎Scale up如用性能更好的主机，或者Scale out增加主机数量通过负载均衡的方式

MySQL的扩展：Scale up的扩展瓶颈很容易突破，在Scale out的扩展方式下，数据如何同步是其核心的管理模块。如下图所示，slave节点向主节点请求二进制日志并在本地replay。应用访问数据库时必须通过7层的读写分离器R/W spliter，能够把应用使用的SQL语句按照按读写类型，把写的请求只发给Master，把读的请求按照负载均衡的方式发送给多个从节点Slaves。

复制的功用：

1. 数据分布
2. 负载均衡读请求
3. 备份
4. 高可用性和故障切换
5. MySQL升级测试

主Master节点：

二进制日志，主服务器必须开启binary log
开启dump Thread：为每个Slave的I/O thread启动一个dump线程，用于向其发送binary log events
单向复制：主-->从

从Slave节点：

IO Thread：从Master请求二进制日志事件，并保存于继日志中
SQL Thread：从中继日志中读取日志事件，在本地完成重放

MySQL复制特点：

异步复制
主从数据不一致比较常见

复制架构：

一主多从
从服务器还可以再有从服务器（第一个从服务器必须开启binary log，同时第一个从服务器使用blackhole存储引擎，不需要存数据，只要记录binary log）
多主环状复制（不常用）

主从复制配置过程：

主节点：
启动二进制日志；
为当前节点设置一个全局唯一的ID号；
创建有复制权限的用户账号(权限是指REPLICATION CLIENT REPLICATION SLAVE )；
从节点
启动中继日志；
为当前节点设置一个全局唯一的ID号；
使用有复制权限的用户账号连接至主服务器，并启动复制线程；

实验1（两个全新的M/S）：

主节点更改/etc/my.cnf配置文件
log-bin = /data/mysqlbinlog/mysql-bin
server_id=1
systemctl restart mysqld
主节点授权
GRANT REPLICATION SLAVE,REPLICATION CLIENT ON . TO 'repluser'@'172.20.%.%' IDENTIFIED BY 'replpass';
FLUSH PRIVILEGES;
从节点更改/etc/my.cnf配置文件
server_id=2 --必须区别于主节目的service_id
relay_log=relay-log
relay_log_index=relay-log.index
read-only
systemctl restart mysqld
检查从节点，确保配置更改
MariaDB [(none)]> SHOW VARIABLES LIKE 'server_id';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| server_id | 2 |
+---------------+-------+
MariaDB [(none)]> SHOW VARIABLES LIKE 'relay_log';
+---------------+-----------+
| Variable_name | Value |
+---------------+-----------+
| relay_log | relay-log |
+---------------+-----------+
MariaDB [(none)]> SHOW VARIABLES LIKE 'relay_log_index';
+-----------------+-------------------------------+
| Variable_name | Value |
+-----------------+-------------------------------+
| relay_log_index | /data/mysqldb/relay-log.index |
+-----------------+-------------------------------+

从节点，开始同步
```
MariaDB [(none)]> HELP CHANGE MASTER TO
MariaDB [(none)]> CHANGE MASTER TO MASTER_HOST='172.20.42.204',MASTER_USER='repluser',MASTER_PASSWORD='replpass',MASTER_LOG_FILE='mysql-bin.000015',MASTER_LOG_POS=685;
MariaDB [(none)]> SHOW SLAVE STATUSG;
*************************** 1. row ***************************
Slave_IO_State:
Master_Host: 172.20.42.204
Master_User: repluser
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000015
Read_Master_Log_Pos: 685
Relay_Log_File: relay-log.000001
Relay_Log_Pos: 4
Relay_Master_Log_File: mysql-bin.000015
Slave_IO_Running: No
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: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 685
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: 0
Last_IO_Error:
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:

MariaDB [(none)]> START SLAVE;
MariaDB [(none)]> SHOW SLAVE STATUSG;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 172.20.42.204
                  Master_User: repluser
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000015
          Read_Master_Log_Pos: 685
               Relay_Log_File: relay-log.000002
                Relay_Log_Pos: 555
        Relay_Master_Log_File: mysql-bin.000015
             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: 685
              Relay_Log_Space: 858
              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
               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)

主节点模拟数据变化
MariaDB [mydb]>create table testtb(name varchar(10),age int);
调用存储过程生成10万行数据：
MariaDB [mydb]> DELIMITER // #修改语句结束符为“//”
MariaDB [mydb]> CREATE PROCEDURE pro_testtb() #写一个存储过程，目的是生成十万条记录测试用
-> BEGIN
-> declare i int;
-> set i = 1;
-> while i < 100000
-> do INSERT INTO testtb(name,age) VALUES (CONCAT('testuser',i),i);
-> SET i = i + 1;
-> END while;
-> END//
MariaDB [mydb]> DELIMITER ; #记得将语句结束符再改回来
MariaDB [mydb]> CALL pro_testtb; #调用存储过程来
MariaDB [mydb]> SELECT COUNT() FROM testtb; #查看一下表中有十万条记录
MariaDB [mydb]> select count() from testtb;
+----------+
| count(*) |
+----------+
| 100000 |
+----------+
从节点上查看同步状态
MariaDB [mydb]> SHOW GLOBAL VARIABLES LIKE 'server_id'; +---------------+-------+ | Variable_name | Value | +---------------+-------+ | server_id | 2 | +---------------+-------+ MariaDB [mydb]> SHOW SLAVE STATUSG; MariaDB [mydb]> SELECT COUNT(*) FROM testtb; +----------+ | COUNT(*) | +----------+ | 100000| +----------+

实验二（模拟生产环境，主库已经有很多的数据，需要扩容只读库满足性能需求）

更改从节点上配置/etc/my.cnf
server_id=3
relay_log=relay-log
relay_log_index=relay-log.index
systemctl restart mysqld
检查从节点，确保配置更改
主节点上做全备
mysqldump -A -F --single-transaction --master-data=2 --flush-privileges > fullbackup.sql
把fullbackup.sql复制到从节点
从节点
更改fullbackup.sql
CHANGE MASTER TO MASTER_HOST='172.20.42.204',MASTER_USER='repluser',MASTER_PASSWORD='replpass',MASTER_LOG_FILE='mysql-bin.000019', MASTER_LOG_POS=385;
mysql < fullbackup.sql
START SLAVE;
检查从同步状态：
MariaDB [mydb]> SHOW SLAVE STATUSG;
Slave_IO_Running: Yes
Slave_SQL_Running: Yes