# Package org.apache.nutch.hostdb

- Interface Summary
  Interface | Description
  --- | ---
  CrawlDatumProcessor | These are instantiated once for each host.

- Class Summary
  Class | Description
  --- | ---
  FetchOverdueCrawlDatumProcessor | Simple custom crawl datum processor that counts the number of records that are overdue for fetching, e.g.
  HostDatum |
  ReadHostDb |
  ResolverThread | Simple runnable that performs DNS lookup for a single host.
  UpdateHostDb | Tool to create a HostDB from the CrawlDB.
  UpdateHostDbMapper | Mapper ingesting HostDB and CrawlDB entries.
  UpdateHostDbReducer |