MySQL 5.6搭建主从复制

使用MySQL 5.6，搭建主从复制。关于5.6的安装，可以参考《MySQL 5.6 rpm安装方法和碰见的问题》。

主库创建slave用户，设置复制权限，

mysql> create user 'slave'@'1.1.1.2' identified by 'root';
Query OK, 0 rows affected (0.00 sec)

mysql> grant replication slave on *.* to 'slave'@'1.1.1.2' identified by 'root';
Query OK, 0 rows affected (0.00 sec)

编辑my.cnf配置文件，设置主库server-id=1，定义需要复制的库为test，忽略mysql数据库

[root@vm-kvm10000-app mysql]# vi /etc/my.cnf

[mysqld]
server-id=1
log-bin=mysql-bin
binlog_do_db=test
binlog_ignore_db=mysql

重启主库MySQL服务，

[root@vm-kvm10000-app mysql]# service mysql restart
Shutting down MySQL.. SUCCESS!
Starting MySQL. SUCCESS!

看一下主库状态，

mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000002 |      120 | test         | mysql            |                   |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)

或者
mysql> show master status \G
*************************** 1. row ***************************
File: mysql-bin.000002
Position: 120
Binlog_Do_DB: test

Binlog_Ignore_DB: mysql
Executed_Gtid_Set:
1 row in set (0.00 sec)

从库，编辑my.cnf配置，设置server-id=2，区别于主库，
[root@vm-kvm10001-app mysql]# vi /etc/my.cnf
[mysqld]
server-id=2

重启MySQL服务，

[root@vm-kvm10001-app mysql]# service mysql restart
Shutting down MySQL.. SUCCESS!
Starting MySQL. SUCCESS!

设置主库信息，

mysql> change master to master_host='1.1.1.1',master_user='slave',master_password='root',master_log_file='mysql-bin.000001',master_log_pos=120,master_connect_retry=10;
Query OK, 0 rows affected, 2 warnings (0.03 sec)

检索从库状态，

mysql> show slave status \G;
*************************** 1. row ***************************
Slave_IO_State:
Master_Host: 10.221.3.129
Master_User: slave
Master_Port: 3306
Connect_Retry: 10
Master_Log_File: mysql-bin.000001
Read_Master_Log_Pos: 120
Relay_Log_File: vm-kvm11853-app-relay-bin.000001
Relay_Log_Pos: 4
Relay_Master_Log_File: mysql-bin.000001
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: 120
Relay_Log_Space: 120
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_UUID:
Master_Info_File: /var/lib/mysql/master.info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State:
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp:
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set:
Executed_Gtid_Set:
Auto_Position: 0
1 row in set (0.00 sec)

其中最重要的就是，这两个参数，要求YES，但此处为NO，
Slave_IO_Running: No
Slave_SQL_Running: No

检索错误日志，提示无法找见./performance_schema/cond_instances.frm文件，
[root@vm-kvm10001-app mysql]# vm-kvm10001-app.err
2017-08-29 16:10:37 22933 [ERROR] /usr/sbin/mysqld: Can't find file: './performance_schema/cond_instances.frm' (errno: 13 - Permission denied)

看一下其目录，发现performance_schema文件夹，是root权限，mysql用户无法访问，因此需要修改一下其权限，
[root@vm-kvm10001-app mysql]# ls -rlht
total 109M
...
drwx------ 2 root  root  4.0K Aug 29 15:05 performance_schema
...

[root@vm-kvm10001-app mysql]# chown -R mysql:mysql *

[root@vm-kvm10001-app mysql]# ls -rlht
total 109M
...
drwx------ 2 mysql mysql 4.0K Aug 29 15:05 performance_schema
...

重启服务，

[root@vm-kvm10001-app mysql]# service mysql restart
Shutting down MySQL.... SUCCESS!
Starting MySQL. SUCCESS!

再看从库状态，

mysql> show slave status \G
*************************** 1. row ***************************
...
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
...

主库导出数据，用于导入从库，首先需要设置读锁，避免数据不一致，

mysql> flush tables with read lock;

mysql> show master logs;
+------------------+-----------+
| Log_name         | File_size |
+------------------+-----------+
| mysql-bin.000001 |       143 |
| mysql-bin.000002 |       222 |
| mysql-bin.000003 |       545 |
+------------------+-----------+
3 rows in set (0.00 sec)

执行mysqldump将test库，导出test.sql文件，
[root@vm-kvm10000-app mysql]# mysqldump -uroot -p -B test > test.sql

然后解锁表，

mysql> unlock tables;

从库执行导入，
[root@vm-kvm10001-app mysql]# mysql -uroot -p < test.sql

要确保从库，这两个值正确，

Slave_IO_Running: Yes    
Slave_SQL_Running: Yes

此时就完成了主从复制，向主库插入一条记录，
mysql> INSERT INTO test
    -> (id, name)
    -> VALUES
    -> (1, "a");
Query OK, 1 rows affected (0.00 sec)

从库中可以检索出来，
mysql> select * from test;

+-------+--------+
|     id    |  name  |
+-------+--------+
|      1    |     a      |
+-------+--------+

总结：
1. MySQL相关文件、文件夹需要的权限，可能会因为不正确，例如需要mysql权限，但却是root，导致数据库异常。

2. 主从复制，需要关注从库，这两个参数值，需要均为YES，出现NO，则可以检索错误日志，进一步定位。

Slave_IO_Running: Yes
Slave_SQL_Running: Yes

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