How to configure Oracle traffic director for full site failover to have high availability?
For a true HA architecture, HTTP traffic must be balanced with a front-end load balancer on a separate host. See here for a list of open source balancers (any of which would be simpler and cheaper to implement than OTD):

https://geekflare.com/open-source-load-balancer/

Oracle DB connections should be configured for high availability failover as described here (use the architecture that best fits your technology stack):

https://www.oracle.com/technetwork/database/availability/client-failover-2280805.pdf

An example of how to implement tomcat's native clustering to compliment the load balancing can be found here on my blog site:

https://pmdba.files.wordpress.com/2019/09/ha-oracle-ords-apex-with-http-header-authentication.pdf