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  1. Hadoop HDFS
  2. HDFS-9705

Refine the behaviour of getFileChecksum when length = 0



    • Type: Improvement
    • Status: Resolved
    • Priority: Minor
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 2.9.0, 3.0.0-alpha4, 2.8.2
    • Component/s: None
    • Labels:


      FileSystem#getFileChecksum may accept length parameter and 0 is a valid value. Currently it will return null when length is 0, in the following code block:

          //compute file MD5
          final MD5Hash fileMD5 = MD5Hash.digest(md5out.getData());
          switch (crcType) {
          case CRC32:
            return new MD5MD5CRC32GzipFileChecksum(bytesPerCRC,
                crcPerBlock, fileMD5);
          case CRC32C:
            return new MD5MD5CRC32CastagnoliFileChecksum(bytesPerCRC,
                crcPerBlock, fileMD5);
            // If there is no block allocated for the file,
            // return one with the magic entry that matches what previous
            // hdfs versions return.
            if (locatedblocks.size() == 0) {
              return new MD5MD5CRC32GzipFileChecksum(0, 0, fileMD5);
            // we should never get here since the validity was checked
            // when getCrcType() was called above.
            return null;

      The comment says "we should never get here since the validity was checked" but it does. As we're using the MD5-MD5-X approach, and EMPTY--CONTENT actually is a valid case in which the MD5 value is d41d8cd98f00b204e9800998ecf8427e, so suggest we return a reasonable value other than null. At least some useful information in the returned value can be seen, like values from block checksum header.


        1. HDFS-9705-v7.patch
          7 kB
          Sammi Chen
        2. HDFS-9705-v6.patch
          7 kB
          Sammi Chen
        3. HDFS-9705-v5.patch
          7 kB
          Kai Zheng
        4. HDFS-9705-v4.patch
          7 kB
          Kai Zheng
        5. HDFS-9705-v3.patch
          7 kB
          Kai Zheng
        6. HDFS-9705-v2.patch
          5 kB
          Kai Zheng
        7. HDFS-9705-v1.patch
          4 kB
          Kai Zheng
        8. HDFS-9705-branch-2.002.patch
          5 kB
          Sammi Chen
        9. HDFS-9705-branch-2.001.patch
          5 kB
          Sammi Chen

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              • Assignee:
                Sammi Sammi Chen
                drankye Kai Zheng
              • Votes:
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                • Created: