public List<ServerName> getOnlineServersList() {
    // TODO: optimize the load balancer call so we don't need to make a new list
    // TODO: FIX. THIS IS POPULAR CALL.
    return new ArrayList<>(this.onlineServers.keySet());
  }
Returns A copy of the internal list of online servers.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/ServerManager.java