protected void suspendRs(ServerName server) throws IOException {
    getLogger().info("Suspending regionserver {}", server);
    cluster.suspendRegionServer(server);
    if (!(cluster instanceof SingleProcessHBaseCluster)) {
      cluster.waitForRegionServerToSuspend(server, killRsTimeout);
    }
    getLogger().info("Suspending regionserver {}. Reported num of rs:{}", server,
      cluster.getClusterMetrics().getLiveServerMetrics().size());
  }
Returns current region servers - active master
hbase-it/src/test/java/org/apache/hadoop/hbase/chaos/actions/Action.java