Step-by-Step Guide to Upgrading MySQL Group Replication (MGR) from 5.7 to 8.0.26

1. Determine MGR mode and version

Check whether the cluster is in single‑primary mode and identify the primary node and each instance's MySQL version.

show variables like '%group_replication_single_primary_mode%';

select * from performance_schema.replication_group_members;

SHOW STATUS LIKE 'group_replication_primary_member';

select @@version;

In MySQL 8 you can verify everything with a single query:

select * from performance_schema.replication_group_members;

2. Backup the database

Perform a full backup before starting the upgrade to allow rollback if needed.

3. Upgrade the first replica

3.1 Install MySQL Shell

Download and install the MySQL Shell package:

https://dev.mysql.com/downloads/repo/yum/
rpm -Uvh mysql80-community-release-el7-3.noarch.rpm
yum install -y mysql-shell

3.2 Check compatibility and fix issues

mysqlsh --util check-for-server-upgrade { --user=root --socket=/opt/mysql/data/3307/mysqld.sock } --target-version=8.0.26 --output-format=JSON --config-path=/opt/mysql/etc/3307/my.cnf

3.3 Stop group replication

stop group_replication;

3.4 Shut down the instance

SET GLOBAL innodb_fast_shutdown=0;
systemctl stop mysqld_3306

3.5 Install the new MySQL binaries

tar xf mysql-8.0.26-linux-glibc2.12-x86_64.tar.xz -C /opt/mysql/base/

Replace the old base directory or symlink:

rm -rf /opt/mysql/base/5.7.25/
ln -s mysql-8.0.26-linux-glibc2.12-x86_64/ /opt/mysql/base/5.7.25

3.6 Start the upgraded instance with auto‑upgrade

/opt/mysql/base/5.7.25/bin/mysqld --defaults-file=/opt/mysql/etc/3306/my.cnf --daemonize --pid-file=/opt/mysql/data/3306/mysqld.pid --user=actiontech-mysql --socket=/opt/mysql/data/3306/mysqld.sock --port=3306 --upgrade=auto

After the upgrade the server does not need a restart, and subsequent starts omit the --upgrade=auto flag.

3.7 Re‑join the replica to the cluster

RESET SLAVE ALL;
set global group_replication_group_name="964fe9c5-03e4-11ec-8aa2-02000aba4034";
SET GLOBAL group_replication_local_address = "10.186.64.71:33061";
SET GLOBAL group_replication_group_seeds = "10.186.64.52:33061";
SET GLOBAL group_replication_bootstrap_group = OFF;
CHANGE MASTER TO MASTER_USER="repl",MASTER_PASSWORD="repl" FOR CHANNEL "group_replication_recovery";
START GROUP_REPLICATION;
select * from performance_schema.replication_group_members;

4. Upgrade the primary node

Repeat the same steps as for the replica. After stopping group replication the primary will automatically fail‑over; verify the new primary before proceeding.

SET GLOBAL group_replication_local_address = "10.186.64.71:33061";
SET GLOBAL group_replication_group_seeds = "10.186.64.52:33061";

5. Change the primary back to the original host (if needed)

SELECT group_replication_set_as_primary('ab8900ff-03e4-11ec-b68a-02000aba4034');

6. Upgrade the communication protocol

After the cluster version is upgraded, the communication protocol remains at the old version and must be updated manually.

6.1 Check current protocol

SELECT group_replication_get_communication_protocol();

6.2 Set the new protocol

SELECT group_replication_set_communication_protocol("8.0.26");

6.3 Verify the change

SELECT group_replication_get_communication_protocol();

Following these steps completes a safe, online, in‑place upgrade of a MySQL 5.7 single‑primary MGR cluster to MySQL 8.0.26.