if (memoryUsage == null) None
      else Some(new GaugeMetric(

Use [Option's apply method](https://github.com/scala/scala/blob/v2.10.1/src/library/scala/Option.scala#L25) instead: ```Option(memPool.getUsage).map(new GaugeMetric......```

You should almost never have to write explicit null checks in Scala.