<#import "/templates/guide.adoc" as tmpl>
<#import "/templates/links.adoc" as links>

<@tmpl.guide
title="Building blocks multi-site deployments"
summary="Overview of building blocks, alternatives and not considered options" >

The following building blocks are needed to set up a multi-site deployment with synchronous replication.

The building blocks link to a blueprint with an example configuration.
They are listed in the order in which they need to be installed.

include::partials/blueprint-disclaimer.adoc[]

== Prerequisites

* Understanding the concepts laid out in the <@links.ha id="concepts-multi-site"/> {section}.

== Two sites with low-latency connection

Ensures that synchronous replication is available for both the database and the external {jdgserver_name}.

*Suggested setup:* Two AWS Availability Zones within the same AWS Region.

*Not considered:* Two regions on the same or different continents, as it would increase the latency and the likelihood of network failures.
Synchronous replication of databases as a services with Aurora Regional Deployments on AWS is only available within the same region.

== Environment for {project_name} and {jdgserver_name}

Ensures that the instances are deployed and restarted as needed.

*Suggested setup:* Red Hat OpenShift Service on AWS (ROSA) deployed in each availability zone.

*Not considered:* A stretched ROSA cluster which spans multiple availability zones, as this could be a single point of failure if misconfigured.

== Database

A synchronously replicated database across two sites.

*Blueprint:* <@links.ha id="deploy-aurora-multi-az"/>.

== {jdgserver_name}

A deployment of {jdgserver_name} that leverages the {jdgserver_name}'s Cross-DC functionality.

*Blueprint:* <@links.ha id="deploy-infinispan-kubernetes-crossdc" /> using the {jdgserver_name} Operator, and connect the two sites using {jdgserver_name}'s Gossip Router.

*Not considered:* Direct interconnections between the Kubernetes clusters on the network layer.
It might be considered in the future.

== {project_name}

A clustered deployment of {project_name} in each site, connected to an external {jdgserver_name}.

*Blueprint:* <@links.ha id="deploy-keycloak-kubernetes" /> that includes connecting to the Aurora database and the {jdgserver_name} server.

</@tmpl.guide>

== Load balancer

A load balancer which checks the `/lb-check` URL of the {project_name} deployment in each site, plus an automation to detect {jdgserver_name} connectivity problems between the two sites.

*Blueprint:* <@links.ha id="deploy-aws-accelerator-loadbalancer"/> together with  <@links.ha id="deploy-aws-accelerator-fencing-lambda"/>.
