This bug was already remarked some posts ago on the mailing list, but thanks anyway for reporting.

I have created issue for keeping track: https://issues.apache.org/jira/browse/NUTCH-1456


On Wed, Aug 15, 2012 at 1:59 PM, lin weijian <linweijian8@gmail.com> wrote:
        i find a bug in nutch 2.0, which causes  Mark.UPDATEDB_MARK could not mark it's bat chid.

        Here in org.apache.nutch.crawl.DbUpdateReducer.java ,  reduce function:

    Utf8 mark = Mark.PARSE_MARK.removeMarkIfExist(page);
    if (mark != null) {
      Mark.UPDATEDB_MARK.putMark(page, mark);

    it clear the generate, fetch & parse bat chid, and set updated bat chid,
    but Mark.UPDATEDB_MARK.putMark(page, mark) could not execute, because
    mark is always null. 

    In gora 0.2, the remove function of StatefulHashMap ,which is called 
     by WebPage's Markers always return null.