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https://issues.apache.org/jira/browse/HBASE-10958?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13970216#comment-13970216
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Lars Hofhansl commented on HBASE-10958:
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Wait. Are you saying the region server itself cannot issue a flush as part of
the bulkLoadHFiles RPC?
The region server is flushing all the time on its own behalf (when the memstore
is full, etc).
> [dataloss] Bulk loading with seqids can prevent some log entries from being
> replayed
> ------------------------------------------------------------------------------------
>
> Key: HBASE-10958
> URL: https://issues.apache.org/jira/browse/HBASE-10958
> Project: HBase
> Issue Type: Bug
> Affects Versions: 0.96.2, 0.98.1, 0.94.18
> Reporter: Jean-Daniel Cryans
> Assignee: Jean-Daniel Cryans
> Priority: Blocker
> Fix For: 0.99.0, 0.94.19, 0.98.2, 0.96.3
>
> Attachments: HBASE-10958-less-intrusive-hack-0.96.patch,
> HBASE-10958-quick-hack-0.96.patch, HBASE-10958-v2.patch, HBASE-10958.patch
>
>
> We found an issue with bulk loads causing data loss when assigning sequence
> ids (HBASE-6630) that is triggered when replaying recovered edits. We're
> nicknaming this issue *Blindspot*.
> The problem is that the sequence id given to a bulk loaded file is higher
> than those of the edits in the region's memstore. When replaying recovered
> edits, the rule to skip some of them is that they have to be _lower than the
> highest sequence id_. In other words, the edits that have a sequence id lower
> than the highest one in the store files *should* have also been flushed. This
> is not the case with bulk loaded files since we now have an HFile with a
> sequence id higher than unflushed edits.
> The log recovery code takes this into account by simply skipping the bulk
> loaded files, but this "bulk loaded status" is *lost* on compaction. The
> edits in the logs that have a sequence id lower than the bulk loaded file
> that got compacted are put in a blind spot and are skipped during replay.
> Here's the easiest way to recreate this issue:
> - Create an empty table
> - Put one row in it (let's say it gets seqid 1)
> - Bulk load one file (it gets seqid 2). I used ImporTsv and set
> hbase.mapreduce.bulkload.assign.sequenceNumbers.
> - Bulk load a second file the same way (it gets seqid 3).
> - Major compact the table (the new file has seqid 3 and isn't considered
> bulk loaded).
> - Kill the region server that holds the table's region.
> - Scan the table once the region is made available again. The first row, at
> seqid 1, will be missing since the HFile with seqid 3 makes us believe that
> everything that came before it was flushed.
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