@Override
  protected void addOptions() {
    this.addRequiredOptWithArg("r", "regionserverhost", "region server <hostname>|<hostname:port>");
    this.addRequiredOptWithArg("o", "operation",
      "Expected: load/unload/unload_from_rack/isolate_regions");
    this.addOptWithArg("m", "maxthreads",
      "Define the maximum number of threads to use to unload and reload the regions");
    this.addOptWithArg("i", "isolateRegionIds",
      "Comma separated list of Region IDs hash to isolate on a RegionServer and put region server"
        + " in draining mode. This option should only be used with '-o isolate_regions'."
        + " By putting region server in decommission/draining mode, master can't assign any"
        + " new region on this server. If one or more regions are not found OR failed to isolate"
        + " successfully, utility will exist without putting RS in draining/decommission mode."
        + " Ex. --isolateRegionIds id1,id2,id3 OR -i id1,id2,id3");
    this.addOptWithArg("x", "excludefile",
      "File with <hostname:port> per line to exclude as unload targets; default excludes only "
        + "target host; useful for rack decommisioning.");
    this.addOptWithArg("d", "designatedfile",
      "File with <hostname:port> per line as unload targets;" + "default is all online hosts");
    this.addOptWithArg("f", "filename",
      "File to save regions list into unloading, or read from loading; "
        + "default /tmp/<usernamehostname:port>");
    this.addOptNoArg("n", "noack",
      "Turn on No-Ack mode(default: false) which won't check if region is online on target "
        + "RegionServer, hence best effort. This is more performant in unloading and loading "
        + "but might lead to region being unavailable for some time till master reassigns it "
        + "in case the move failed");
    this.addOptWithArg("t", "timeout", "timeout in seconds after which the tool will exit "
      + "irrespective of whether it finished or not;default Integer.MAX_VALUE");
  }
Remove the servername whose hostname and port portion matches from the passed array of servers.
Returns as side-effect the servername removed.
@return server removed from list of Region Servers
hbase-server/src/main/java/org/apache/hadoop/hbase/util/RegionMover.java