Setting Up MySQL 8.0 to MySQL 5.7 Replication

This article demonstrates how to set up replication from MySQL 8.0 (master) to MySQL 5.7 (slave), which can be useful in upgrade or master‑master migration scenarios.

Supported version matrix :

master 5.7 → slave 8.0 : supported

master 8.0 → slave 5.7 : not supported

Because MySQL replication only works between consecutive major versions and from lower to higher, the only viable direction for a mixed‑version topology is 5.7 master to 8.0 slave; however, the article shows how to make 8.0 → 5.7 work by adjusting settings.

Character set and collation changes – MySQL 8 defaults to utf8mb4 and utf8mb4_0900_ai_ci . To avoid “character set not compiled” errors on the slave, modify the master’s my.cnf :

[client]
default-character-set=utf8
[mysqld]
character-set-server=utf8
collation-server=utf8_unicode_ci

Restart MySQL 8.0 after editing the configuration.

Authentication plugin – MySQL 8 uses caching_sha2_password by default, which MySQL 5.7 does not understand. Create the replication user with the legacy mysql_native_password plugin:

CREATE USER 'replica_user'@'%' IDENTIFIED WITH mysql_native_password BY 'repli$cat';
GRANT REPLICATION SLAVE ON *.* TO 'replica_user'@'%';

Change master command – after the user is created, run on the slave:

CHANGE MASTER TO MASTER_HOST='127.0.0.1',
MASTER_USER='replica_user',
MASTER_PASSWORD='repli$cat',
MASTER_PORT=19025,
MASTER_LOG_FILE='mysql-bin.000007',
MASTER_LOG_POS=155;
START SLAVE;

For GTID‑enabled setups you can use MASTER_AUTO_POSITION = 1 instead of specifying log file and position.

Verification – check the replication status on the slave:

SHOW SLAVE STATUS\G

Key fields such as Slave_IO_Running and Slave_SQL_Running should be Yes , and Last_Errno should be 0.

Quick test – create a test database on the master and confirm it appears on the slave:

CREATE DATABASE vinnie;
SHOW DATABASES LIKE 'vinnie';

Important notes – using MySQL 8 features like RULE , invisible indexes, or caching_sha2_password will cause replication to stop with errors such as Last_SQL_Errno: 1396 . Stick to the legacy authentication plugin for cross‑version replication.

Conclusion – Replication from MySQL 8.0 to MySQL 5.7 is possible with the adjustments described, but it is not recommended for heterogeneous topologies because of compatibility risks.