void initializeXidMetric(final AtomicLong currentXid) {
    helixClusterManagerCurrentXid = currentXid::get;
    registry.gauge(MetricRegistry.name(HelixClusterManager.class, "currentXid"), () -> helixClusterManagerCurrentXid);
  }
Metrics for the {@link HelixClusterManager}
@param registry The {@link MetricRegistry} associated with the {@link HelixClusterManager}
@param  clusterMapCallback The {@link HelixClusterManagerQueryHelper} used to query information
                           from {@link HelixClusterManager}
ambry-clustermap/src/main/java/com/github/ambry/clustermap/HelixClusterManagerMetrics.java