Thanks, Andrew Wang. The metrics system takes a class name as the source/sink to start. It's then instantiated in complete isolation. That works fine in reality, but it's ugly for testing. The alternative to the static suppliedConf is to have the test write out a configuration file and then convince the metrics system to read it. That's also pretty ugly.
On the suppliedFilesystem variable, I still don't exactly understand why I need it. When using a secure mini-cluster, if I try to use FileSystem.get(), all operations fail with a checksum error. Know anything about that?
I have thought about making the interval configurable. And now that you've asked the question, I guess I gotta. Would number of minutes be a reasonable way to configure the rollover interval?