@Override
    public synchronized Clock updateHWMark(String source, long hwm) {
        _sourceWaterMarks.saveHWMark(source, hwm);
        return current();
    }
@ Override public synchronized Clock updateHWMark ( String source , long hwm ) { _sourceWaterMarks . saveHWMark ( source , hwm ) ; return current ( ) ; }
Save the high water mark of a given source.

@param source
@param hwm