The image shows an Oracle Cloud Infrastructure (OCI) architecture that automates failover to show a custom maintenance page for applications running on OCI. The arhitecture comprises the following components:

• A region

  • A virtual cloud network (VCN) within the region
    • A public subnet (10.0.1.0/26) within the VCN
      • Users reach applications by using an Internet Gateway and an OCI Load Balancer.
      • The OCI Load Balancer exposes Listener 1 (Application) and Listener 2 (Maintenance Page), and forwards requests to the virtual machines or the OCI API Gateway.
    • A private subnet (10.0.1.64/26) within the VCN
      • Two (or more) OCI Virtual Machine (VM) instances serve applications as the load balancer backends.
      • OCI API Gateway provides a mechanism to serve a custom error page to the load balancer via Listener 2.
      • OCI Functions runs automation that updates the load balancer ruleset by calling the API.
  • An OCI Service Gateway enables private access from within the VCN to the services in the Oracle Services Network (OSN).

• Within the region but outside the VCN, OSN is shown with the following OCI Monitoring services:

  • Alarms uses an alarm definition to monitor OCI Load Balancer metrics and determine health of the backend VMs. Alarms are sent to OCI Notifications.
  • OCI Notifications sends a message that triggers OCI Functions when an alarm occurs.