[HBASE-22582] The Compaction writer may access the lastCell whose memory has been released when appending fileInfo in the final

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0.0-alpha-1, 2.3.0, 2.0.6, 2.2.1, 2.1.6
• Component/s: Compaction
• Hadoop Flags: Reviewed
• Assignee: Zheng Hu
• Reporter: Zheng Hu
• Created: 14/Jun/19 07:47
• Updated: 01/Jul/22 21:47
• Resolved: 04/Jul/19 07:03

Description

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:

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);
}

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

Compactor#commitWriter
    －> HFileWriterImpl#close
         －> HFileWriterImpl#writeFileInfo
               －> HFileWriterImpl#finishFileInfo

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);
  }
  ...
}

Because the lastCell may refer to a reused ByteBuff.

Checked the code, It's a bug and will need to fix in all 2.x & master branch.

Issue Links

• relates to: HBASE-21879 Read HFile's block to ByteBuffer directly instead of to byte for reducing young gc purpose
• links to: GitHub Pull Request #341