public boolean isOnline() {
    return online.get();
  }
Report the status of the server. A server is online once all the startup is completed (setting
up filesystem, starting executorService threads, etc.). This method is designed mostly to be
useful in tests.
@return true if online, false if not.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegionServer.java