We concepts behind clustering are [here](https://gluu.org/docs/gluu-server/4.2/installation-guide/cluster/)
The [code for Cluster Manager](https://github.com/GluuFederation/cluster-mgr), or commercial deployment tool is source available. This tool automates many of the steps described in the docs referenced above.
You can also use the Gluu [Kubernetes Instructions](https://gluu.org/docs/gluu-server/4.2/installation-guide/install-kubernetes/)
Beyond this, clustering is deemed a requirement for enterprise customers, and a commercial support contract is necessary.