[jira] [Commented] (HBASE-16931) Setting cell's seqId to zero in compaction flow might cause RS down.

["Anoop Sam John (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-16931?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15625068#comment-15625068 ] 

Anoop Sam John commented on HBASE-16931:
----------------------------------------

bq.We dont clone the seqId and all cloned cells will give seqId of 0!.
Seems there is no issue. Only this method affects the mentioned area
{code}
public static KeyValue toNewKeyCell(final Cell cell) {
    byte[] bytes = new byte[keyLength(cell)];
    appendKeyTo(cell, bytes, 0);
    KeyValue kv = new KeyValue.KeyOnlyKeyValue(bytes, 0, bytes.length);
    // Set the seq id. The new key cell could be used in comparisons so it
    // is important that it uses the seqid also. If not the comparsion would fail
    kv.setSequenceId(cell.getSequenceId());
    return kv;
  }
{code}
And we are copying the seqId also. So all good

> Setting cell's seqId to zero in compaction flow might cause RS down.
> --------------------------------------------------------------------
>
>                 Key: HBASE-16931
>                 URL: https://issues.apache.org/jira/browse/HBASE-16931
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver
>    Affects Versions: 2.0.0, 1.3.0
>            Reporter: binlijin
>            Assignee: binlijin
>            Priority: Critical
>             Fix For: 2.0.0, 1.3.0, 1.4.0, 1.2.4, 1.1.8
>
>         Attachments: HBASE-16931-master.patch, HBASE-16931.branch-1.patch, HBASE-16931.branch-1.v2.patch, HBASE-16931_master_v2.patch, HBASE-16931_master_v3.patch, HBASE-16931_master_v4.patch, HBASE-16931_master_v5.patch
>
>
> Compactor#performCompaction
>       do {
>         hasMore = scanner.next(cells, scannerContext);
>         // output to writer:
>         for (Cell c : cells) {
>           if (cleanSeqId && c.getSequenceId() <= smallestReadPoint) {
>             CellUtil.setSequenceId(c, 0);
>           }
>           writer.append(c);
>         }
>         cells.clear();
>       } while (hasMore);
> scanner.next will choose at most "hbase.hstore.compaction.kv.max" kvs, the last cell still reference by StoreScanner.prevCell, so if cleanSeqId is called when the scanner.next call StoreScanner.checkScanOrder may throw exception and cause regionserver down.



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