protected final void ack(Tuple t, String url) {
        // keep the URL in the cache
        if (useCache) {
            cache.put(url, "");
        }

        _collector.ack(t);
    }
protected final void ack ( Tuple t , String url ) { if ( useCache ) { cache . put ( url , "" ) ; } _collector . ack ( t ) ; }
Must be called by extending classes to store and collect in one go