[NUTCH-2391] Spurious Duplications for MD5

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.11
• Fix Version/s: 1.14
• Component/s: commoncrawl
• Assignee: Sebastian Nagel
• Reporter: David Johnson
• Created: 05/Jun/17 18:08
• Updated: 13/Mar/24 14:51
• Resolved: 05/Jul/17 15:29

Description

We're seeing some incidence of a large number of documents being marked as duplicate in our crawl.

We traced it back to one of the crawl plugins returning an empty array for the content field.

We'd like to propose changing the MD5 signature generation from:

public byte[] calculate(Content content, Parse parse) {
    byte[] data = content.getContent();
    if (data == null)
      data = content.getUrl().getBytes();
    return MD5Hash.digest(data).getDigest();
  }

to:

public byte[] calculate(Content content, Parse parse) {
    byte[] data = content.getContent();
    if ((data == null) || (data.length == 0))
      data = content.getUrl().getBytes();
    return MD5Hash.digest(data).getDigest();
  }

to address the issue

Issue Links

• is related to: NUTCH-2393 2.x patch for MD5 duplication issue addressed in NUTCH-2391