https://wiki.shibboleth.net/confluence/display/IDP30/Jetty93#Jetty93-JettyLogging
The above wiki page recommends "logback for all Jetty logging"
Considering that 3 of the 4 libraries recommended to use are already provided with the IdP - it would be nice to have the final package (logback-access) included with distribution and the documentation changed to simply borrow these files (I've simply used symlinks in the JETTY_BASE/lib/logging/) - rather than also having to manual maintaining components that are mostly already provided.