private void initReporting() {
    if (!(initCodahaleMetricsReporterClasses() || initMetricsReporter())) {
      LOGGER.warn("Unable to initialize metrics reporting");
    }
    if (reporters.isEmpty()) {
      // log a warning incase no reporters were successfully added
      LOGGER.warn("No reporters configured for codahale metrics!");
    }
  }
Initializes reporters from HIVE_CODAHALE_METRICS_REPORTER_CLASSES or HIVE_METRICS_REPORTER if the former is not defined.
Note: if both confs are defined, only  HIVE_CODAHALE_METRICS_REPORTER_CLASSES will be used.
standalone-metastore/metastore-common/src/main/java/org/apache/hadoop/hive/common/metrics/metrics2/CodahaleMetrics.java