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https://issues.apache.org/jira/browse/BOOKKEEPER-572?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13633665#comment-13633665
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Sijie Guo commented on BOOKKEEPER-572:
--------------------------------------
{quote}
This problem (assuming your referring to corrupt journal entry) is easily
handled the same way we handle it today. If LedgerStorage#addEntry throws an
IOException, send an error back to the client,
{quote}
the problem is you only get the exception after added the entry to journal. so
the entry lives in journal. when bookie started, replaying this journal tried
to add the entry to ledger storage, but it would failed. so the bookie could
not start.
{quote}
I like the COW idea. This is effectively what the skiplists do. However, I
think we should continue to support interleaved and skiplist for the moment
anyhow.
{quote}
the COW is just for ledger index. it works for both skiplists and interleaved.
> Make the journal a write ahead log
> ----------------------------------
>
> Key: BOOKKEEPER-572
> URL: https://issues.apache.org/jira/browse/BOOKKEEPER-572
> Project: Bookkeeper
> Issue Type: Bug
> Reporter: Ivan Kelly
> Assignee: Ivan Kelly
> Fix For: 4.3.0
>
> Attachments:
> 0001-BOOKKEEPER-572-Write-to-the-journal-before-writing-t.patch,
> 0001-BOOKKEEPER-572-Write-to-the-journal-before-writing-t.patch,
> 0001-BOOKKEEPER-572-Write-to-the-journal-before-writing-t.patch,
> 0001-BOOKKEEPER-572-Write-to-the-journal-before-writing-t.patch,
> 0003-BOOKKEEPER-572-Write-to-the-journal-before-writing-t.patch,
> 0003-BOOKKEEPER-572-Write-to-the-journal-before-writing-t.patch,
> BookieServer-2013-02-22.snapshot
>
>
> A bookie adds to the LedgerStorage before writing to the journal. This is the
> fundamental problem behind BOOKKEEPER-447 and blocks a nice solution to
> BOOKKEEPER-530. By writing to the memory state before the journal, we exposed
> ourselves to bugs if the bookie crashed before we wrote to the journal. The
> entry may exist in index, but not in the entrylog, a situation which cannot
> be distinguished from an I/O error. The comments on BOOKKEEPER-447 goes into
> more details.
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