Add Sensible Java Metaspace Size Limit to fits-ngserver.sh

[jpellman]

The FITS nailgun wrapper is currently running using the Java 8 defaults. Under these defaults, there is no limit to the max metaspace size. This leads to the unfortunate side effect that if FITS is under heavy use it might cause out-of-memory errors due to the metaspace eating up all of the host's RAM. It might make sense to have this wrapper use the -XX:MaxMetaspaceSize= parameter when starting up Nailgun along with a sensible value based off the available RAM on the host.

[pwinckles]

@jpellman Have you tried setting that parameter? If so, did it actually work? Metaspace is not supposed to grow unbound. I would expect that putting a limit on it would just cause the service to OOM sooner than later. I wonder if this is an issue that's unique to running FITS through nailgun, or if it's a general problem. It would likely be useful to see what's eating the metaspace. This could either be erroneous class loading, or native allocations that are not being reclaimed (likely culprits for the native allocations are MediaInfo and nailgun itself).