private void refreshSummary(ClusterMetrics clusterMetrics) {
    String currentTime = ISO_8601_EXTENDED_TIME_FORMAT.format(EnvironmentEdgeManager.currentTime());
    String version = clusterMetrics.getHBaseVersion();
    String clusterId = clusterMetrics.getClusterId();
    int liveServers = clusterMetrics.getLiveServerMetrics().size();
    int deadServers = clusterMetrics.getDeadServerNames().size();
    int regionCount = clusterMetrics.getRegionCount();
    int ritCount = clusterMetrics.getRegionStatesInTransition().size();
    double averageLoad = clusterMetrics.getAverageLoad();
    long aggregateRequestPerSecond = clusterMetrics.getLiveServerMetrics().entrySet().stream()
      .mapToLong(e -> e.getValue().getRequestCountPerSecond()).sum();

    summary = new Summary(currentTime, version, clusterId, liveServers + deadServers, liveServers,
      deadServers, regionCount, ritCount, averageLoad, aggregateRequestPerSecond);
  }
The data and business logic for the top screen.
hbase-hbtop/src/main/java/org/apache/hadoop/hbase/hbtop/screen/top/TopScreenModel.java