long getMaxSize(HiveConf conf) {
    return MetastoreConf.getLongVar(conf, MetastoreConf.ConfVars.REPL_METRICS_CACHE_MAXSIZE);
  }
MetricCollector.
In memory collection of metrics
ql/src/java/org/apache/hadoop/hive/ql/parse/repl/metric/MetricCollector.java