Solved: Jetty doesn’t show errors on web application start-up
From a certain version of the "jetty" package in Debian Linux, if the web application didn't start up (servlet init() throws an Exception), this error wasn't logged anywhere. The solution is to install the libjetty-extra package.
sudo apt-get install libjetty-extra
It took some amount of experimentation to find the solution. I don't know why you'd ever want to not log errors; i.e. why the logging of errors is an "extra".
Jetty is a Java web server, similar to Tomcat, it's my server of choice. It's simple, doesn't seem to do much apart from run WARs, and (apart from this issue) I've rarely had any problems with it.