We should think a bit about the right way to expose the "rebuild a UI" logic inside of Spark. The first goal here is that the existing standalone cluster manager should, once an application completes, be able to re-render the existing UI for that application. The ideal semantics would be that you can just point to a directory in HDFS known to contain the logs and have it add new handlers to an existing jetty server. Right now the SparkUI starts its own server always so that might need to be altered. 

A second goal is to have simple standalone version that can run in it's own JVM that basically "watches" a base directory and reports new applications as they arrive. This one would also need to create multiple SparkUI's in the same JVM.