[keycloak-user] Return 503 (Service Unvailable) instead of 404 (File Not found) during keycloak server restarts

[Thomas Darimont]

Hello group,

the undertow servlet-container is started pretty early during the startup
of the
wildfly application server. However the initialization of the keycloak
server
application might take a while to complete. Within this period requests
that are
sent to the keycloak endpoints result in responses with HTTP Status Code
404.

Is it possible to configure undertow to return a HTTP Status Code 503
(Service Unvailable)
until the keycloak application startup has completed?

This would ease configuring load-balancers and to avoid showing a 404
to users during server restarts.

Cheers,
Thomas