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  1. Hadoop Common
  2. HADOOP-16049

DistCp result has data and checksum mismatch when blocks per chunk > 0

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    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 2.9.2
    • Fix Version/s: 2.9.3
    • Component/s: tools/distcp
    • Labels:
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      Description

      In 2.9.2 RetriableFileCopyCommand.copyBytes,

      int bytesRead = readBytes(inStream, buf, sourceOffset);
      while (bytesRead >= 0) {
        ...
        if (action == FileAction.APPEND) {
          sourceOffset += bytesRead;
        }
        ... // write to dst
        bytesRead = readBytes(inStream, buf, sourceOffset);
      }

      it does a positioned read but the position (`sourceOffset` here) is never updated when blocks per chunk is set to > 0 (which always disables append action). So for chunk with offset != 0, it will keep copying the first few bytes again and again, causing result to have data & checksum mismatch.

      To re-produce this issue, in branch-2, update BLOCK_SIZE to 10240 (> default copy buffer size) in class TestDistCpSystem and run it.

      HADOOP-15292 has resolved the issue reported in this ticket in trunk/branch-3.1/branch-3.2 by not using the positioned read, but has not been backported to branch-2 yet

       

       

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