Implementing Active-Active replication with SQL Galera Cluster for load balancing

26 Sep 2023

Load balancing is a crucial aspect of modern applications that need to handle high traffic and ensure high availability. When it comes to databases, implementing active-active replication can help distribute the workload and provide seamless failover capabilities.

One way to achieve active-active replication is by using SQL Galera Cluster, a multi-master synchronous replication solution for MySQL or MariaDB databases. In this blog post, we will explore how to set up SQL Galera Cluster to achieve load balancing in a highly available configuration.

Prerequisites

Before we begin, make sure you have the following prerequisites in place:

Three or more servers running MySQL or MariaDB with a compatible version.
Each server should have a dedicated network interface for Galera traffic.
A common storage backend, such as network-attached storage (NAS) or a clustered file system.

Step 1: Install SQL Galera Cluster

The first step is to install SQL Galera Cluster on each server. Follow the installation instructions specific to your operating system and distribution. Ensure that you install the same version of SQL Galera Cluster on every server.

Step 2: Configure Galera Cluster

Once the installation is complete, configure Galera Cluster on each server. Open the configuration file (usually located at /etc/mysql/my.cnf) and make the following adjustments:

Set the cluster name using the wsrep_cluster_name directive. For example: wsrep_cluster_name=my_cluster.
Specify the addresses of all the nodes in the cluster using the wsrep_cluster_address directive. Example: wsrep_cluster_address=gcomm://node1_ip,node2_ip,node3_ip.
Set the network interface for Galera traffic using the wsrep_provider_options directive. Example: wsrep_provider_options="gcache.size=256M; gcs.fc_limit=1000; evs.keepalive_period=PT3S; evs.suspect_timeout=PT10S".
Enable Galera Cluster by setting wsrep_on to ON.

Step 3: Start Galera Cluster

After configuring Galera Cluster on all servers, start the cluster by running the following command on each node:

$ sudo systemctl start mysql

Ensure that all nodes start successfully without any errors. You can check the status of the cluster using the following command:

$ sudo systemctl status mysql

Step 4: Load Balancing

With Galera Cluster up and running, you can now configure your applications to connect to the cluster for load balancing. You can achieve this by using a load balancer such as HAProxy or Nginx.

Configure your load balancer to distribute incoming database connections across nodes in the Galera Cluster. Ensure that the load balancer is properly configured for session persistence so that the same client is directed to the same database node throughout a session.

Conclusion

By implementing active-active replication with SQL Galera Cluster, you can achieve load balancing and high availability for your database infrastructure. With proper configuration and setup, you can distribute the workload across multiple nodes and ensure seamless failover in case of any node failures.

Remember to regularly monitor the health and performance of your Galera Cluster and make adjustments as needed. By doing so, you can ensure that your database infrastructure is robust and can handle high volumes of traffic effectively.

#loadbalancing #galeracluster