I have a WildFly installation which takes some time during startup due to the count and size of the deployments. So I would like to show a maintenance page until the full application is ready.
In one of the previous WildFly versions I used default-web-module
as configuration option and registered a small WAR file, which was visible right away and was replaced as soon as the big application was available.
Unfortunately this is no longer possible with WildFly 22, instead an exception is thrown as soon as the real root application is deployed:
org.jboss.msc.service.DuplicateServiceException: Service jboss.undertow.deployment.default-server.default-host./.UndertowDeploymentInfoService is already registered
I know that I could put a small web server (nginx or similar) in front of WildFly to return my maintenance webpage as long as WildFly returns a 503 error. The only thing which prevents that is the fact, that the maintenance page still contains some logic which I would need to emulate on nginx.
Is there any other option which ensures that my maintenance page is delivered immediately while the other apps are still starting?