窥探MySQL集群之主从复制

1 MySQL之主从复制

1.1 MySQL主从复制

1.1.1 MySQL主从复制架构及原理

• 性能扩展
  • 服务性能扩展方式： Scale Up ，Scale Out
• MySQL的扩展
  • 读写分离
  • 复制：每个节点都有相同的数据集，向外扩展，基于二进制日志的单向复制
  • 复制的功用
    • 数据分布
    • 负载均衡读
    • 备份
    • 高可用和故障切换
    • MySQL升级测试
• 复制架构
  • 一主一从复制架构
    
  • 一主一从复制架构
    
• 主从复制原理
  

1.1.2 实现MySQL主从复制配置

• 参考官网
  • https://mariadb.com/kb/en/library/setting-up-replication/
  • https://dev.mysql.com/doc/refman/5.5/en/replication-configuration.html

1.2.2.1 主节点配置

系统选用的CentOS8

• (1) 启用二进制日志

vim /etc/my.cnf.d/mariadb-server.cnf 
[mysqld]
server_id=1 # 为当前节点设置一个全局惟一的ID号
log_bin=/data/mysql/logbin/mysql-bin #启用二进制日志，及其日志存放路径（根据个人来选择二进制日志存放位置）
binlog_format=row
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
log-error=/var/log/mariadb/mariadb.log
pid-file=/run/mariadb/mariadb.pid
# 保存退出
systemctl start mariadb

• （2）创建有复制权限的用户账号
  语法：

GRANT REPLICATION SLAVE ON *.* TO 'repluser'@'HOST' IDENTIFIED BY 'replpass';
#范例：
# MariaDB [(none)]> grant replication slave on *.* to repluser@'192.168.66.%' identified by 'magedu';
Query OK, 0 rows affected (0.001 sec)
# MariaDB [(none)]> select host,user,password from mysql.user;
+--------------+----------+-------------------------------------------+
| host         | user     | password                                  |
+--------------+----------+-------------------------------------------+
| localhost    | root     |                                           |
| centos8      | root     |                                           |
| 127.0.0.1    | root     |                                           |
| ::1          | root     |                                           |
| 192.168.66.% | repluser | *6B8CCC83799A26CD19D7AD9AEEADBCD30D8A8664 |
+--------------+----------+-------------------------------------------+
# MariaDB [(none)]> show master logs;
+------------------+-----------+
| Log_name         | File_size |
+------------------+-----------+
| mysql-bin.000001 |       529 |
+------------------+-----------+

1.2.2.2 从节点配置

系统选用的CentOS7

• (1) 启用中继日志

# vim /etc/my.cnf.d/server.cnf
[mysqld]
server_id=# #为当前节点设置一个全局惟的ID号
read_only=ON #设置数据库只读，针对supper user无效
relay_log=relay-log #relay log的文件路径，默认值hostname-relay-bin
relay_log_index=relay-log.index #默认值hostname-relay-bin.index
# systemctl restart mariadb.service

+（2）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
语法：

CHANGE MASTER TO MASTER_HOST='host',
MASTER_USER='repluser',
MASTER_PASSWORD='replpass',
MASTER_LOG_FILE='mariadb-bin.xxxxxx',
MASTER_LOG_POS=#;
#范例：    #范例内容与主节点相对应
change master to master_host='192.168.66.8',
master_user='repluser',
master_password='magedu',
master_port=3306,
master_log_file='mysql-bin.000001',
master_log_pos=529;

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

show slave status;
MariaDB [(none)]> show slave status\G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.66.8
                  Master_User: repluser
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000001
          Read_Master_Log_Pos: 529
               Relay_Log_File: mariadb-relay-bin.000002
                Relay_Log_Pos: 540
        Relay_Master_Log_File: mysql-bin.000001
             Slave_IO_Running: Yes # 当前主要观察项
            Slave_SQL_Running: Yes # 当前主要观察项
              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: 529
              Relay_Log_Space: 836
              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 #复制的延迟时间
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)

1.1.3 实验 ：主服务器非新建时，实现主从

• 如果主节点已经运行了一段时间，且有大量数据时，如何配置并启动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
• 范例：
  • 主服务器运行一段时间后，新增从节点服务器

#在主服务器完全备份
[root@master ~]#mysqldump -A -F --single-transaction --master-data=1 >
/backup/fullbackup_`date +%F_%T`.sql
[root@master ~]#ll /backup/
total 2988
-rw-r--r-- 1 root root 3055918 Nov 27 17:41 fullbackup_2019-11-27_17:41:17.sql
[root@master ~]#scp /data/backup/fullbackup_2019-11-28_17\:37\:31.sql  192.168.66.18:/data
#将完全备份还原到新的从节点
[root@slave ~]#dnf -y install mariadb-server
[root@slave ~]#vim /etc/my.cnf.d/mariadb-server.cnf
[mysqld]
server-id=18
read-only
[root@slave ~]#systemctl restart mariadb

#配置从节点，从完全备份的位置之后开始复制
[root@slave ~]#grep -i '^change master' /data/fullbackup_2019-11-28_17\:37\:31.sql 
CHANGE MASTER TO MASTER_LOG_FILE='mariadb-bin.000003', MASTER_LOG_POS=389;

[root@slave ~]#vim /data/fullbackup_2019-11-28_17\:37\:31.sql

# CHANGE MASTER TO
  MASTER_HOST='192.168.66.8',
  MASTER_USER='repluser',
  MASTER_PASSWORD='magedu',
  MASTER_PORT=3306,
# MASTER_LOG_FILE='mariadb-bin.000003', MASTER_LOG_POS=389; 
**注意：**
	上述注释的两行在备份文件中是存在的，所以将change master to 语句中的其他部分补上
[root@slave ~]#mysql < /data/fullbackup_2019-11-28_17\:37\:31.sql
**注意**
	 经自己实验CentOS8与CentOS7可能存在差异，当导入完全备份时报错，不可导入。（有可能是我人品差）
[root@slave ~]#mysql
MariaDB [(none)]> start slave;
Query OK, 0 rows affected (0.001 sec)

MariaDB [(none)]> show slave status\G;
*************************** 1. row ***************************
                Slave_IO_State: Waiting for master to send event
                   Master_Host: 192.168.66.8
                   Master_User: repluser
                   Master_Port: 3306
                 Connect_Retry: 60
               Master_Log_File: mariadb-bin.000003
           Read_Master_Log_Pos: 389
                Relay_Log_File: mariadb-relay-bin.000002
                 Relay_Log_Pos: 557
         Relay_Master_Log_File: mariadb-bin.000003
              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: 389
               Relay_Log_Space: 868
               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
              Slave_DDL_Groups: 0
Slave_Non_Transactional_Groups: 0
    Slave_Transactional_Groups: 0
1 row in set (0.001 sec)

1.1.4 主从复制相关

1. 限制从服务器只读

read_only=on
#注意：此限制对拥有super权限的用户均无效

注意：以下命令会阻止所有用户，包括主服务器复制的更新

FLUSH TABLES WITH READ LOCK;

2.在从节点清除信息

• 注意：以下都需要先 STOP SLAVE

RESET SLAVE #从服务器清除master.info ，relay-log.info, relay log ，开始新的relay log
RESET SLAVE ALL #清除所有从服务器上设置的主服务器同步信息，如PORT, HOST, USER和PASSWORD 等

3.复制错误解决方法

• 可以在从服务器忽略几个主服务器的复制事件，此为global变量

sql_slave_skip_counter = N #global
[mysqld]
slave_skip_errors=1007|ALL # 静态，需写进配置文件

范例：
1.构建错误，先在从服务器创建一个错误：

MariaDB [(none)]> create database db4;
Query OK, 1 row affected (0.001 sec)

2.再在主服务器上构建

MariaDB [(none)]> create database db4;
Query OK, 1 row affected (0.001 sec)

3.从服务器上查看slave状态

MariaDB [(none)]> show slave status\G;
*************************** 1. row ***************************
                Slave_IO_State: Waiting for master to send event
                   Master_Host: 192.168.66.8
                   Master_User: repluser
                   Master_Port: 3306
                 Connect_Retry: 60
               Master_Log_File: mariadb-bin.000003
           Read_Master_Log_Pos: 643
                Relay_Log_File: mariadb-relay-bin.000002
                 Relay_Log_Pos: 684
         Relay_Master_Log_File: mariadb-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 #错误代码
                    Last_Error: Error 'Can't create database 'db4'; database exists' on query. Default database: 'db4'. Query: 'create database db4' # 错误信息
                  Skip_Counter: 0
           Exec_Master_Log_Pos: 516
               Relay_Log_Space: 1122
               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 #错误代码
                Last_SQL_Error: Error 'Can't create database 'db4'; database exists' on query. Default database: 'db4'. Query: 'create database db4' #错误信息
   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_DDL_Groups: 2
Slave_Non_Transactional_Groups: 0
    Slave_Transactional_Groups: 0
1 row in set (0.000 sec)

ERROR: No query specified

4.解决方法

#方法1
MariaDB [(none)]> stop slave;  需停掉该线程
MariaDB [(none)]> set global sql_slave_skip_counter=1;
MariaDB [(none)]> start slave;
#方法2
[root@slave1 ~]#vim /etc/my.cnf.d/mariadb-server.cnf
[mysqld]
slave_skip_errors=1007|ALL
[root@slave1 ~]#systemctl restart mariadb

方法1实例如下

# 从服务操作
MariaDB [(none)]> stop slave;
Query OK, 0 rows affected (0.002 sec)

MariaDB [(none)]> set global sql_slave_skip_counter=1;
Query OK, 0 rows affected (0.001 sec)

MariaDB [(none)]> start slave;
Query OK, 0 rows affected (0.002 sec)
#主服务操作
MariaDB [(none)]> create database db5;
Query OK, 1 row affected (0.001 sec)
#从操作
MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| db1                |
| db2                |
| db3                |
| db4                |
| db5                |
| hellodb            |
| information_schema |
| mysql              |
| performance_schema |
+--------------------+
9 rows in set (0.001 sec)
**发现实现同步**

1.1.5 保证主从复制的事务安全

参看：https://mariadb.com/kb/en/library/server-system-variables/

• 1 在master节点启用参数

sync_binlog=1 每次写后立即同步二进制日志到磁盘，性能差
#如果用到的为InnoDB存储引擎：
innodb_flush_log_at_trx_commit=1 #每次事务提交立即同步日志写磁盘
innodb_support_xa=ON #分布式事务MariaDB10.3.0废除
sync_master_info=# #次事件后master.info同步到磁盘

• 2 在slave节点启用服务器选项

skip-slave-start=ON #不自动启动slave

• 3 在slave节点启用参数

sync_relay_log=# #次写后同步relay log到磁盘
sync_relay_log_info=# #次事务后同步relay-log.info到磁盘