[HIVE-17169] Avoid extra call to KeyProvider::getMetadata()

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.0.0
• Fix Version/s: 2.3.2, 2.4.0, 3.0.0
• Component/s: Shims
• Hadoop Flags: Reviewed
• Assignee: Mithun Radhakrishnan
• Reporter: Mithun Radhakrishnan
• Created: 25/Jul/17 17:23
• Updated: 23/May/18 00:00
• Resolved: 16/Aug/17 17:30

Description

Here's the code from Hadoop23Shims:

Hadoop23Shims.java

    @Override
    public int comparePathKeyStrength(Path path1, Path path2) throws IOException {
      EncryptionZone zone1, zone2;

      zone1 = hdfsAdmin.getEncryptionZoneForPath(path1);
      zone2 = hdfsAdmin.getEncryptionZoneForPath(path2);

      if (zone1 == null && zone2 == null) {
        return 0;
      } else if (zone1 == null) {
        return -1;
      } else if (zone2 == null) {
        return 1;
      }

      return compareKeyStrength(zone1.getKeyName(), zone2.getKeyName());
    }

    private int compareKeyStrength(String keyname1, String keyname2) throws IOException {
      KeyProvider.Metadata meta1, meta2;

      if (keyProvider == null) {
        throw new IOException("HDFS security key provider is not configured on your server.");
      }

      meta1 = keyProvider.getMetadata(keyname1);
      meta2 = keyProvider.getMetadata(keyname2);

      if (meta1.getBitLength() < meta2.getBitLength()) {
        return -1;
      } else if (meta1.getBitLength() == meta2.getBitLength()) {
        return 0;
      } else {
        return 1;
      }
    }
  }

It turns out that EncryptionZone already has the cipher's bit-length stored in a member variable. One shouldn't need an additional name-node call (KeyProvider::getMetadata()) only to fetch it again.