public void process(DocumentUpdate update) {
        if (log.isLoggable(Level.FINE)) {
            log.log(Level.FINE, "Ignored " + update);
        }
    }
Override this to process DocumentUpdates. If this method is not overridden, the implementation in this class
will ignore DocumentUpdates (passing them through un-processed). If processing of this DocumentUpdate fails, the
implementation must throw a {@link RuntimeException}.

@param update the DocumentUpdate to process.
docproc/src/main/java/com/yahoo/docproc/SimpleDocumentProcessor.java