MySQL Upgrade from 8.0.4 to 8.4.x (RHEL) Internet

This article describes the steps, checks, and dependencies required to upgrade MySQL from version 8.0.4 to 8.4.x on RHEL 8 systems. It covers prerequisites, pre-upgrade tasks, upgrade execution, post-upgrade validations, and rollback procedures to ensure a safe and reliable production upgrade.

Prerequisites

OS Compatibility

Verify that the operating system supports MySQL 8.4.
Recommended: RHEL 8.x or later.
Check the OS version:
```
cat /etc/os-release
```

System Requirements

Ensure sufficient disk space for backup and rollback (df -Th).
Confirm root or sudo access.
All listed commands must be executed.

Pre-Upgrade Checks

Backup

Perform a logical backup of the MySQL database.
Log Management Procedure

Confirm you are backing up the correct schema.

mkdir /home/ec2-user/mysql_backup  
mysqldump -u root -p ovaledgedb > /home/ec2-user/mysql_backup/ovaledgedb_backup.sql

Ensure sufficient space is available before running the mysqldump command.

Back up configuration files:

sudo cp /etc/my.cnf /home/ec2-user/mysql_backup/  
sudo cp -a /var/lib/mysql /home/ec2-user/mysql_backup/

Database Size and Row Count Check

Run the following queries before upgrading:

Database size query:

SELECT 
    table_schema AS "Database Name", 
    ROUND(SUM(data_length + index_length) / 1024 / 1024, 1) AS "DB Size (MB)"
FROM information_schema.tables 
GROUP BY table_schema;

Row count query: (Download SQL script)

Save outputs for post-upgrade comparison.

Upgrade Execution

Stop MySQL Services

Stop MySQL services by running the following command

mysql --version  
sudo systemctl stop mysqld

Install MySQL 8.4.x

Download repository package:

wget https://dev.mysql.com/get/mysql84-community-release-el8-1.noarch.rpm

Install repository:

sudo yum localinstall mysql84-community-release-el8-1.noarch.rpm

Disable any existing MySQL 8.0 repositories:

sudo vi /etc/yum.repos.d/mysql-community.repo
# enable=0 (disable) / enable=1 (enabled)

Disable MySQL module in the package manager:
```
sudo yum module disable mysql -y
```
Install MySQL 8.4.x:
```
sudo yum install mysql-community-server
```
Check installed version:
```
mysql --version
```

Update Configuration

Edit the configuration file:

sudo vi /etc/my.cnf
mysql_native_password=ON

Save file and restart MySQL:

sudo systemctl restart mysqld  
sudo systemctl status mysqld

Verify upgrade by checking MySQL version.

Post-Upgrade Validations

Verify Row Counts and Database Size

Connect to MySQL:
```
mysql -u root -p
```

Run validation queries:

Row count query: SQL Script

Database size query:

SELECT 
    table_schema AS "Database Name", 
    ROUND(SUM(data_length + index_length) / 1024 / 1024, 1) AS "DB Size (MB)"
FROM information_schema.tables 
GROUP BY table_schema;

Compare results with pre-upgrade outputs.

Update MySQL Parameters

Add/update parameters in /etc/my.cnf:

max_binlog_size=1GB
binlog_expire_logs_seconds=2592000
group_concat_max_len=50000
max_connections=600
innodb_buffer_pool_size=10GB
max_allowed_packet=1G
bind-address=0.0.0.0

Adjust values as per client instance size.
Restart MySQL:
```
sudo systemctl restart mysqld
```

Update Application User Passwords (Optional)

Change OvalEdge MySQL user passwords:

ALTER USER 'ovaledge'@'localhost' IDENTIFIED BY '<Password>';  
ALTER USER 'ovaledge'@'%' IDENTIFIED BY '<Password>';  
FLUSH PRIVILEGES;

At this stage, the MySQL database has been upgraded to version 8.4 and the default OvalEdge MySQL password has been changed.

Rollback Plan (if required)

Take backup of MySQL 8.4 installation before rollback:

mkdir /home/ec2-user/mysql8.4_backup  
sudo cp /etc/my.cnf /home/ec2-user/mysql8.4_backup  
sudo cp -a /var/lib/mysql /home/ec2-user/mysql8.4_backup

Stop MySQL services, reinstall MySQL 8.0.4, start the service, and restore data from backups.

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