MySQL database master-slave configuration

1. Install MySQL database
2. Modify the master database configuration
1. Set the service id in /etc/my.cnf (note: ensure that it is inconsistent with the slave database), restart the database

2. Query the basic data of the database master, and save the records for backup;
(1).mysql -u(userName)-p enter the database command line

(2). Enter show master status; query master data

Record file, Position data file "binlog.000015" and offset "2832";
3. Create a cross-domain account to ensure that the slave server can log in to the mysql database of the master server
createuser 'rep'@'%' identified by '1234567'; ----Create a mysql user for synchronization from the server
grant replication slave,replication client on . to 'rep'@'%'; ----Authorized created user permissions
(Note: If it is mysql8.0 or later, the encryption method needs to be modified, the command is as follows: alter user 'root'@'%' identified with mysql_native_password by 'root';)
flush privileges; ------ Immediately refresh the permissions to make the permissions changes take effect immediately
3. Modify the configuration of the slave database
1. Install the database on the slave server (guarantee the same version as the master database)
2. Log in to the main database cross-domain to ensure that the new cross-domain account can be used mysql -h "ip" -u"userName" -p
Entering the mysql data line means the link is successful

3. Modify the configuration of the slave database, the server_id is guaranteed to be inconsistent with the master database, and restart the database

4. If it is a newly installed database, it does not need to be processed, and the master-slave relationship is set directly. If there is data in the database, it needs to be synchronously initialized first, that is, to ensure that the contents of the master and slave databases are consistent;
5. Enter the commandLine to set the master-slave relationship
change master to master_host='the ip of the server where the master database is located', master_user='the account name of the set cross-domain account', master_password='password', master_log_file='in the master database masterfile name', master_log_pos='offset of master database master';

6. Start the slave server process
start slave;
7. View the slave server process status
show slave statusG;

Slave_IO_Running: write status
Slave_SQL_Running: local database running status
When both statuses are yes, it proves that the database master-slave status is set successfully
(1) If the Slave_IO_Running status is connecting, checkThe communication status of the two servers, if the ping result is normal, check the firewall status of the two servers, adjust the external access rights of the firewall or directly close the firewall (both master and slave servers need to be adjusted);
If the status of Slave_IO_Running is No, you need to check the error information, there are too many error information in the log, you can see the latest one displayed in the slave status

According to the error information;
(2) If the Slave_SQL_Running status is No, it is generally caused by the inconsistency of the initial data of the master and slave databases

In this state, you can try to close the slave database process;
stop slave;
Back up the master database, import the slave database, make the master and slave databases consistent, and then restart;
start slave;
> View the status of the slave database;
If an error is still reported, you can execute the skip process command;
set global sql_slave_skip_counter=1;
After restarting, query the status, and repeat the skip command if the same type of error is reported. Generally,Adjust 2-3 times;
4. Test
When the status is normal, you can add, delete, modify and check the database in the master database, and then check the data status of the database in the slave database.Completed from configuration.
Five, gtid-based master-slave relationship
When configuring the settings file of the master database, you need to configure the following parameters:
From the database settings file, the configuration parameters are as follows:

When changing the master parameter from the database, replace the master_log_file and master_log_pos parameters with the master_auto_position parameter (1. When using GTID-based replication MASTER_AUTO_POSITION = 1 2. After using GTID, want to revert to the old file-based replication protocol MASTER_AUTO_POSITION =0);

After the modification is completed, start the slave database process, start slave; check the running status of the slave database, show slave statusG;

The status is normal, you can test it;
Reference: https://zhuanlan.zhihu.com/p/335142300

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