code: public void init() throws ConfigurationException {
  		if(index == null) {
  			throw new ConfigurationException("No index target");
  		}
  		if(!index.isUpdatable()) {
  			throw new ConfigurationException("ResourceIndex is not updatable");
  		}
  		if(incoming == null) {
  			throw new ConfigurationException("No incoming");			
  		}
  		if(runInterval > 0) {
  			thread = new UpdateThread(this,runInterval);
  			thread.start();
  		}
  	}
docs: start the background index merging thread
  @throws ConfigurationException