Major Description
Tez UI can throw a 503 error when hosted on a server that cannot reach public IPs like java.sun.com which are listed as servers for DTDs in web.xml. This behavior change comes from moving to jetty 9 (Tez and Hadoop 3.0) which removed provided schemas that were being shipped with earlier versions. It is suboptimal even in cases where public IPs are accessible to fetch the DTD for a very very simple web.xml file. We can choose to either remove the DTD validation or add dependency explicitly to org.eclipse.jetty.toolchain ยป jetty-osgi-servlet-api to allow for this jetty change to not affect the behavior of tez-ui.