synchronized JvmMetrics init(String processName, String sessionId) {
      if (impl == null) {
        impl = create(processName, sessionId, DefaultMetricsSystem.instance());
      }
      return impl;
    }
JVM and logging related metrics. Ported from Hadoop JvmMetrics.
Mostly used by various servers as a part of the metrics they export.
common/src/java/org/apache/hadoop/hive/common/JvmMetrics.java