Setting Up MySQL Replication: Master-Slave Configuration

Configuring the master

Creating users and granting privileges

CREATE USER 'repl'@'%' IDENTIFIED BY 'password';
GRANT REPLICATION SLAVE ON *.* TO 'repl'@'%';
FLUSH PRIVILEGES;
FLUSH TABLES WITH READ LOCK;

Getting the master status

SHOW MASTER STATUS;

The result should look like this:

+---------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+---------------+----------+--------------+------------------+-------------------+
| binlog.000002 | 1151   |            |               |                 |
+---------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)

Configuring the slave

CHANGE MASTER TO MASTER_HOST='[master_ip]', MASTER_USER='repl', MASTER_PASSWORD='password', MASTER_LOG_FILE='[log_file_from_master]', MASTER_LOG_POS=[log_position_from_master];

In this example, the host name of master is master (name of the docker container) which will be automatically resolved to master's IP, the log file is binlog.000002 and the log position is 1151.

CHANGE MASTER TO MASTER_HOST='master', MASTER_USER='repl', MASTER_PASSWORD='password', MASTER_LOG_FILE='binlog.000002', MASTER_LOG_POS=1151;
START SLAVE;

Note: we used master as the hostname because we are using docker-compose and the containers are on the same network.

Testing the replication

Create a new table on the master:

CREATE TABLE test (id INT NOT NULL PRIMARY KEY AUTO_INCREMENT, name VARCHAR(255));

Insert some data:

INSERT INTO test (name) VALUES ('test');
INSERT INTO test (name) VALUES ('test2');

Now, check and see if the data is replicated on the slave:

SELECT * FROM test;

If you do not see the data, check the slave status:

SHOW SLAVE STATUS;