In a MariaDB Galera Cluster, asynchronous replication is not a built-in feature. Galera Cluster uses a synchronous multi-master replication approach, meaning all nodes in the cluster have the same data at the same time. However, if you want to set up asynchronous replication alongside the Galera Cluster, you can do so by creating a separate MariaDB server acting as a standalone asynchronous replica.
Here's a general outline of the steps to configure asynchronous replication alongside a MariaDB Galera Cluster:
Set up a new MariaDB server: Install and configure another MariaDB server that will serve as the asynchronous replica.
Enable binary logging: On the asynchronous replica server, make sure to enable binary logging by adding the following line to the my.cnf or my.ini configuration file under the [mysqld] section:
log-bin=mysql-bin
Set up replication user: Create a user on the Galera Cluster that will be used by the asynchronous replica to connect and replicate data. For example:
CREATE USER 'replication_user'@'asynchronous_replica_ip' IDENTIFIED BY 'password';
GRANT REPLICATION SLAVE ON *.* TO 'replication_user'@'asynchronous_replica_ip';
FLUSH PRIVILEGES;
Replace asynchronous_replica_ip with the IP address or hostname of the asynchronous replica server.
Restart MariaDB: After making these changes, restart the MariaDB server on the asynchronous replica to apply the configurations.
Connect and set up replication: On the asynchronous replica server, connect to the Galera Cluster as the replication user and set up the replication:
CHANGE MASTER TO MASTER_HOST='galera_cluster_ip', MASTER_USER='replication_user', MASTER_PASSWORD='password', MASTER_LOG_FILE='mysql-bin.xxxxxx', MASTER_LOG_POS=xxxx;
Replace galera_cluster_ip with the IP address or hostname of one of the Galera nodes.
Replace mysql-bin.xxxxxx with the binary log file and position information you want to start replication from. You can find this information on the Galera node by running SHOW MASTER STATUS;.
Start replication: After setting up the replication configuration, start the replication process on the asynchronous replica:
START SLAVE;
Verify replication: Monitor the replication status on the asynchronous replica using the following command:
SHOW SLAVE STATUS\G
Check the Slave_IO_Running and Slave_SQL_Running fields to ensure that both are Yes, indicating that replication is working correctly.
Please note that asynchronous replication can lead to data discrepancies between the Galera Cluster and the asynchronous replica, especially in cases of failures or conflicts. Use this approach with caution and ensure you have a solid backup and disaster recovery strategy in place. It is generally recommended to stick with Galera Cluster's synchronous replication for high availability and data consistency. Asynchronous replication is more suitable for scenarios where a delay in replication and potential data inconsistency can be tolerated.
