Practical case: using MYCAT to realize read-write separation of MySQL

 Practical cases ： utilize  Mycat  Realization  MySQL  Separation of reading and writing 

System environment of all hosts ：

[[email protected] ~]# cat /etc/centos-release
CentOS Linux release 8.3.2011

There are three servers in total

client       10.0.0.7
mycat-server 10.0.0.8 # Memory recommendations 2G above 
mysql-master 10.0.0.18 MySQL 8.0 
mysql-slave  10.0.0.28 MySQL 8.0 

close SELinu And the firewall

systemctl stop firewalld
setenforce 0
 Time synchronization 

1. establish MySQL Master slave database

# master server 
[[email protected] ~]# yum -y install mysql-server
[[email protected] ~]# systemctl enable --now mysqld
# From the server 
[[email protected] ~]# yum -y install mysql-server
[[email protected] ~]# systemctl enable --now mysqld

1) modify master and slave Configuration file on

#master Upper my.cnf
[[email protected] ~]# vim /etc/my.cnf
[mysqld]
server-id=18
[[email protected] ~]# systemctl restart mysqld
#slave Upper my.cnf
[[email protected] ~]# vim /etc/my.cnf
[mysqld]
server-id=28
[[email protected] ~]# systemctl restart mysqld

2)Master Create a replication user on （10.0.0.8）

[[email protected] ~]# mysql
mysql> show master logs;
+---------------+-----------+-----------+
| Log_name      | File_size | Encrypted |
+---------------+-----------+-----------+
| binlog.000001 |       179 | No        |
| binlog.000002 |       156 | No        |
+---------------+-----------+-----------+
2 rows in set (0.00 sec)
mysql> create user r[email protected]'10.0.0.%' identified by '123456' ;
mysql> grant replication slave on *.* to [email protected]'10.0.0.%';

3) Slave On the implementation （10.0.0.18）

[[email protected] ~]# mysql
mysql> CHANGE MASTER TO
  MASTER_HOST='10.0.0.18',
  MASTER_USER='repluser',
  MASTER_PASSWORD='123456',
  MASTER_PORT=3306,
  MASTER_LOG_FILE='binlog.000002',
  MASTER_LOG_POS=156;
mysql> start slave;
mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for source to send event
                  Master_Host: 10.0.0.18
                  Master_User: repluser
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: binlog.000002
          Read_Master_Log_Pos: 11277
               Relay_Log_File: slave-relay-bin.000002
                Relay_Log_Pos: 11442
        Relay_Master_Log_File: binlog.000002
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
... Omit ...

2、 stay MySQL proxy server 10.0.0.8 install mycat And start the

[[email protected] ~]# yum -y install java
[[email protected] ~]# java -version
# Confirm successful installation 
openjdk version "1.8.0_312"
OpenJDK Runtime Environment (build 1.8.0_312-b07)
OpenJDK 64-Bit Server VM (build 25.312-b07, mixed mode)

# Download and install 
[[email protected] ~]# wge thttp://dl.mycat.org.cn/1.6.7.6/20210303094759/Mycat-server-1.6.7.6-release-20210303094759-linux.tar.gz
[[email protected] ~]# mkdir /apps
[[email protected] ~]# tar xvf Mycat-server-1.6.7.6-release-20210303094759-linux.tar.gz -C /apps/

# Configure environment variables 
[[email protected] ~]# echo 'PATH=/apps/mycat/bin:$PATH' > /etc/profile.d/mycat.sh
[[email protected] ~]# . /etc/profile.d/mycat.sh

# start-up mycat   Be careful :  This step starts slowly , It's going to take a while , In addition, if the memory is too small , Will result in failure to start    Recommended memory 3G
[[email protected] ~]# mycat start
Starting Mycat-server...

# Check the log , Confirm success , It may take a while to see the hint of success 
[[email protected] ~]# tail -f  /apps/mycat/logs/wrapper.log 
INFO   | jvm 1    | 2021/12/25 00:22:40 | MyCAT Server startup successfully. see logs in logs/mycat.log

# Use the default password 123456 To connect mycat
[[email protected] ~]# mysql -uroot -p123456 -h10.0.0.8 -P8066
mysql> show databases;
+----------+
| DATABASE |
+----------+
| TESTDB   |
+----------+
1 row in set (0.00 sec)

4、 stay mycat Modify on server server.xml File configuration Mycat Connection information (10.0.0.8)

... Omit ...
# Delete Note , And modify the following line 8066 Change it to 3306  
[[email protected] ~]# cat /apps/mycat/conf/server.xml
<property name="serverPort">3306</property>
 46             <property name="managerPort">3306</property>
 47             <property name="idleTimeout">300000</property>
 48             <property name="authTimeout">15000</property>
 49             <property name="bindIp">0.0.0.0</property>
 50             <property name="dataNodeIdleCheckPeriod">300000</property>  # Delete  5 * 60 * 1000L; // Connection free check    Delete # The following part 

110   <user name="root" defaultAccount="true">    # Connect mycat Username 
111     <property name="password">magedu</property>   # Connect mycat Password  
112     <poperty name="schemas">TESTDB</property>    # The database name should be the same as schema.xml Corresponding  
... Omit ...
125     </user>

What we use here is root, The password for magedu, The logical database is TESTDB, This information can be defined at will , Both read and write permissions

Yes , There is no special permission for the table . Focus on the above configuration , Other defaults are ok .

5、 modify schema.xml Implement the read-write separation strategy （10.0.0.8）

[[email protected] ~]# vim /apps/mycat/conf/schema.xml
<!DOCTYPE mycat:schema SYSTEM "schema.dtd">
<mycat:schema xmlns:mycat="http://io.mycat/">
<schema name="TESTDB" checkSQLschema="***false***" sqlMaxLimit="100"
dataNode="***dn1***"></schema>
<dataNode name="dn1" dataHost="localhost1" database="***mycat***" />  # among mycat surface 
 Show the actual database name of the back-end server 
<dataHost name="localhost1" maxCon="1000" minCon="10" balance="***1***"
writeType="0" dbType="mysql" dbDriver="native" switchType="1"
slaveThreshold="100">
<heartbeat>select user()</heartbeat>
***<writeHost host="host1" url="10.0.0.18:3306" user="root"
password="123456">***
***<readHost host="host2" url="10.0.0.28:3306" user="root" password="123456"
/>***
</writeHost>
</dataHost>
</mycat:schema>
# above *** Part indicates the content to be modified in the original configuration file 
# Pay attention to case 

# Final document content 
<?xml version="1.0"?>
<!DOCTYPE mycat:schema SYSTEM "schema.dtd">
<mycat:schema xmlns:mycat="http://io.mycat/">    
	<schema name="TESTDB" checkSQLschema="false" sqlMaxLimit="100" dataNode="dn1">	
	</schema>	
	<dataNode name="dn1" dataHost="localhost1" database="hellodb" />		
	<dataHost name="localhost1" maxCon="1000" minCon="10" balance="1"
	writeType="0" dbType="mysql" dbDriver="native" switchType="1"  slaveThreshold="100">
		<heartbeat>select user()</heartbeat>		
		<writeHost host="host1" url="10.0.0.18:3306" user="root" password="123456">
         <readHost host="host2" url="10.0.0.28:3306" user="root" password="123456" />     
		</writeHost>
			</dataHost>
</mycat:schema>

# Restart mycat
[[email protected] ~]# mycat restart

In the above configuration ,balance Change it to 1, It means separation of reading and writing . The effect of the above configuration is 10.0.0.18 Give priority to the library ,10.0.0.28 by

Slave Library

Be careful ： Be sure to use root/123456 Permission successfully logged in 10.0.0.18 and 10.0.0.28 On top of the machine mysql database . meanwhile ,

And you have to empower mycat Machines can use root/123456 Permission to successfully log in to these two machines mysql database ！！ It's important , no

Will cause login mycat after , Operation on Library and table failed ！

Example ：schema.xml

6. Create a user on the back-end master server and update it mycat to grant authorization （10.0.0.18）

[[email protected] ~]# mysql
mysql> create [email protected]'10.0.0.%' identified by '123456';
mysql> grant all on *.* to [email protected]'10.0.0.%'; 

7、 Connect and test on the client (10.0.0.7)

[[email protected] ~]# mysql -uroot -pmagedu -h10.0.0.8
mysql> show databases;
+----------+
| DATABASE |
+----------+
| TESTDB   |
+----------+
1 row in set (0.00 sec)
mysql> use TESTDB;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> show tables;
+-------------------+
| Tables_in_hellodb |
+-------------------+
| classes           |
| coc               |
| courses           |
| scores            |
| students          |
| teachers          |
| toc               |
+-------------------+

8. Read / write separation is realized through general log confirmation

stay mysql View the general log in

# Check whether the slow log is enabled 
mysql> show variables like 'general%';
+------------------+--------------------------+
| Variable_name    | Value                    |
+------------------+--------------------------+
| general_log      | OFF                       |
| general_log_file | /var/lib/mysql/slave.log |
+------------------+--------------------------+
2 rows in set (0.01 sec)
# Open slow log 
mysql> set global general_log =1;
#
mysql> show variables like 'general_log_file';
+------------------+--------------------------+
| Variable_name    | Value                    |
+------------------+--------------------------+
| general_log_file | /var/lib/mysql/slave.log |
+------------------+--------------------------+
1 row in set (0.00 sec)

Enable common logging on master and slave servers respectively , View read write separation

[[email protected] ~]#vim /etc/my.cnf.d/mariadb-server.cnf
[mysqld]
general_log=ON
[[email protected] ~]#systemctl restart mariadb
[[email protected] ~]#tail -f /var/lib/mysql/centos8.log

9、 Stop from node ,MyCAT Automatically schedule read requests to the master node

[[email protected] ~]#systemctl stop mysqld
[[email protected] ~]#mysql -uroot -pmagedu -h10.0.0.8 -P8066
mysql> select @@server_id;
+-------------+
| @@server_id |
+-------------+
|          1 |
+-------------+ 1 row in set (0.00 sec)
mysql> 
# Stop master ,MyCAT Write requests to the slave node are not automatically scheduled 
MySQL [TESTDB]> insert teachers values(5,'wang',30,'M');
ERROR 1184 (HY000): java.net.ConnectException: Connection refused

10、MyCAT Health check methods for back-end servers select user()

# Open the general log 
[[email protected] ~]#mysql
mysql> set global  general_log=1;
[[email protected] ~]#mysql
mysql> set global  general_log=1;

# View general log 
[[email protected] ~]# tail -f /var/lib/mysql/master.log
/usr/libexec/mysqld, Version: 8.0.26 (Source distribution). started with:
Tcp port: 3306  Unix socket: /var/lib/mysql/mysql.sock
Time                 Id Command    Argument
2022-01-02T15:42:42.887840Z	   60 Query	select user()
2022-01-02T15:42:52.889744Z	   58 Query	select user()
2022-01-02T15:43:02.887842Z	   57 Query	select user()

[[email protected] ~]# tail -f /var/lib/mysql/slave.log 
/usr/libexec/mysqld, Version: 8.0.26 (Source distribution). started with:
Tcp port: 3306  Unix socket: /var/lib/mysql/mysql.sock
Time                 Id Command    Argument
2021-12-25T17:38:29.668676Z	   45 Query	select user()
2021-12-25T17:38:32.291701Z	   46 Query	show variables like 'general%'
2021-12-25T17:38:39.670626Z	   42 Query	select user()
2021-12-25T17:38:49.669060Z	   43 Query	select user()
2021-12-25T17:38:59.673280Z	   44 Query	select user()