private void add(final List<String> servers) throws IOException {
    synchronized (this.drainingServers) {
      this.drainingServers.clear();
      for (String n : servers) {
        final ServerName sn = ServerName.valueOf(ZKUtil.getNodeName(n));
        this.drainingServers.add(sn);
        this.serverManager.addServerToDrainList(sn);
        LOG.info("Draining RS node created, adding to list [" + sn + "]");

      }
    }
  }
Starts the tracking of draining RegionServers.
<p>
All Draining RSs will be tracked after this method is called.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/DrainingServerTracker.java