mariadb master-slave replication (the master database already has data)

A certain database in the production environment of the company needs to perform master-slave replication on the basis of the existing data in the master database. When it comes to the production environment, be cautious, so first test it in the test environment and record the operation process by the way.

1. Install the slave database

The main library already exists, the intranet IP is 10.200.9.183, and the slave library is ready to be built on 10.200.9.188.

(1) Download and unzip the database compression package

The database version used is mariadb-10.0.33, download method:

wget https://downloads.mariadb.com/MariaDB/mariadb-10.0.33/bintar-linux-x86_64/mariadb-10.0.33-linux-x86_64.tar.gz

Unzip the database compressed package:

tar  -xzvf  mariadb-10.0.33-linux-x86_64.tar.gz 

Move to the specified location:

mv mariadb-10.0.33-linux-x86_64 /data/mariadb-10.0.33

(2) Change configuration

Backup the default database configuration file under /etc:

mv /etc/my.cnf  /etc/my.cnf.bak

Copy the configuration file template in the database to /etc/

cp support-files/my-innodb-heavy-4G.cnf  /etc/my.cnf

Edit configuration file

vim /etc/my.cnf

Change the following

basedir=/data/mariadb-10.0.33
datadir=/data/mariadb-10.0.33/data

(3) Create a mysql user and change permissions

Create a mysql user:

useradd -s /sbin/nologin -M mysql

Change the user and group of all mysql files to mysql

chown -R mysql:mysql /data/mariadb-10.0.33

Specify user and file path to initialize mysql

./scripts/mysql_install_db  --basedir=/data/mariadb-10.0.33 --datadir=/data/mariadb-10.0.33/data/ --user=mysql

(4) Set the startup script to start mysql

Mariadb provides a startup script. In the support-files directory of the installation directory, the file name is mysql.server, and copy it to /etc/init.d

cp support-files/mysql.server /etc/rc.d/init.d/mysqld

Start mysql

/etc/init.d/mysqld start

or

service mysqld start

mysql startup self-start setting:

chkconfig --add mysqld
chkconfig mysqld on

Check whether mysql is added to the startup list:

chkconfig --list

As shown below, the addition is successful

(5) mysql root user authorization:

Login to mysql

/data/mariadb-10.0.33/bin/mysql -u root

Authorization:

grant all privileges on *.* to 'root'@'%' identified by '123456';
grant all privileges on *.* to 'root'@'localhost' identified by '123456';
grant all privileges on *.* to 'root'@'127.0.0.1' identified by '123456';

Refresh permissions:

flush privileges;

(6) Add the mysql command to the environment variable

Edit the /etc/profile file:

vim /etc/profile

Add the following to the last line

export PATH=$PATH:/data/mariadb-10.0.33/bin

Refresh environment variables

source /etc/profile

2. Main library settings

(1) Edit the main library configuration file:

vim /etc/my.cnf

Configure the binlog file name:

log-bin = mysql-bin

Set the server-id (server-id must be unique and cannot be duplicated from the library):

server-id = 1

Set master-slave synchronization to synchronize only a certain database

binlog-do-db = newenergy

Set the binlog expiration time:

expire_logs_days = 2

Set log format

binlog_format = mixed

• statement saves the SQL statement
• row saves the impact record data
• The combination of the first two is
  recommended to be set to mxed mode

(2) Create an account with copy permissions

IP is from the library IP

GRANT REPLICATION SLAVE,REPLICATION CLIENT ON *.* TO 'repluser'@' 10.200.9.188' IDENTIFIED BY 'replpass';

Refresh permissions

FLUSH PRIVILEGES;

Restart the database

service mysqld restart

4. Set from the library

(1) Edit the configuration file from the library

vim /etc/my.cnf

Set relay log relay-log

relay-log = relay-bin

Set server-id (server-id must be unique, and cannot conflict with the main library and other slave libraries):

server-id = 2

(2) Restart the database
service mysqld restart

5. Synchronize the main database from the database

(1) Lock the main library so that it has only read-only permissions.

flush table with read lock;

(2) Check the master status and remember the backup point

The content in the red box needs to be kept and recorded, and the backup is started from this place.

(3) Back up the main database

Because only one database is synchronized, it is sufficient to back up this one database.

mysqldump -uroot -p123456 newenergy > newenergy.sql

(4) Unlock table

unlock tables;

(5) Import the backup from the library

mysql -uroot -p123456
source newenergy.sql

(6) From the library to the main library

It is recommended to use the SQL statement "CHANGE MASTER TO" to modify the relevant configuration. The main modifications are:

• master_host: master host IP
• master_port: port of the master database
• master_user: The user name used by the slave to connect to the master for authentication
• master_password: the password used by the slave to connect to the master for authentication
• master_log_file: The name of the master binary log
• master_log_pos: the starting position of the binary log where the slave starts to replicate

The setting contents of the latter two parameters master_log_file and master_log_pos are the contents of File and Position that were previously required to be retained during show master status.
Log in to the slave database

mysql -u root -p123456

Connect to the main library

 CHANGE MASTER TO MASTER_HOST='10.200.9.183',MASTER_USER='repluser',MASTER_PASSWORD='replpass',MASTER_LOG_FILE='mysql-bin.000002',master_port=3307,MASTER_LOG_POS=154;

(7) Start the slave

start slave;

(8) View slave status

show slava status\G;

As shown below, both Slave_SQL_Running and Slave_IO_Running show Yes to prove that the slave successfully connected to the master.

(9) Troubleshooting

If Slave_IO_Running does not display yes, Last_IO_Error will display the cause of the error, as shown in the figure:
Here the server-id of the master-slave database of the table name is duplicated, and one of the server-id needs to be modified and restarted.
This means that it cannot be connected to the main database, which may be due to the failure of the main database port or the unreachable IP. Check whether the slave library can be connected to the master library.

6. Check whether the synchronization is successful

Create a table or add a field in the newenergy database of the main library, and you can see it in the slave library to indicate that the synchronization is successful. You can also see the synchronization delay by viewing the value of Seconds_Behind_Master.