code: public void setOnline(boolean isOnline, boolean allowQuery, boolean dropStaleIndexes) throws IOException
     {
        handler.setOnline(isOnline, allowQuery, dropStaleIndexes);
     }
docs: Switches index into corresponding ONLINE or OFFLINE mode. Offline mode means that new indexing data is
  collected but index is guaranteed to be unmodified during offline state. Passing the allowQuery flag, can
  allow or deny performing queries on index during offline mode. AllowQuery is not used when setting index
  back online. When dropStaleIndexes is set, indexes present on the moment of switching index offline will be
  marked as stale and removed on switching it back online.
  
  @param isOnline
  @param allowQuery
  doesn't matter, when switching index to online
  @param dropStaleIndexes
  doesn't matter, when switching index to online
  @throws IOException