Zheng Hu created HBASE-22582:
--------------------------------

             Summary: The Compaction writer may access the lastCell whose 
memory has been released when appending fileInfo in the final
                 Key: HBASE-22582
                 URL: https://issues.apache.org/jira/browse/HBASE-22582
             Project: HBase
          Issue Type: Bug
            Reporter: Zheng Hu


Copy the comment from [~javaman_chen] under HBASE-21879: 
https://issues.apache.org/jira/browse/HBASE-21879?focusedCommentId=16862244&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-16862244

In Compactor#compact, we have the following:

{code}
protected List<Path> compact(final CompactionRequest request...
  ...
  try {
    ...
  } finally {
    Closeables.close(scanner, true);
    if (!finished && writer != null) {
      abortWriter(writer);
    }
  }
  assert finished : "We should have exited the method on all error paths";
  assert writer != null : "Writer should be non-null if no error";
  return commitWriter(writer, fd, request);
}
{code}
should we call writer#beforeShipped() before Closeables.close(scanner, true);
In order to copy some cell's data out of the ByteBuff before it released, or 
commitWriter may be wrong in the following call stack

{code}
Compactor#commitWriter
    -> HFileWriterImpl#close
         -> HFileWriterImpl#writeFileInfo
               -> HFileWriterImpl#finishFileInfo
{code}

{code}
protected void finishFileInfo() throws IOException {
  if (lastCell != null) {
    // Make a copy. The copy is stuffed into our fileinfo map. Needs a clean
    // byte buffer. Won't take a tuple.
    byte [] lastKey = 
PrivateCellUtil.getCellKeySerializedAsKeyValueKey(this.lastCell);
    fileInfo.append(FileInfo.LASTKEY, lastKey, false);
  }
  ...
}
{code}
Because the lastCell may refer to a reused ByteBuff. 



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