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https://issues.apache.org/jira/browse/BOOKKEEPER-572?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13626785#comment-13626785
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Flavio Junqueira commented on BOOKKEEPER-572:
---------------------------------------------
I'm sorry for joining the discussion late, but I'm not convinced of the problem
reported here. The description says:
{noformat}
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
{noformat}
My recollection of ZOOKEEPER-447 is that it is about flushing the index before
the entries, but the case here is different. I don't think having an entry in
the ledger device and not in the journal is a problem. The journal is there to
guarantee durability; if it is already in the ledger device, it is not a
problem to not have it in the journal. What am I missing?
> 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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