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https://issues.apache.org/jira/browse/HDFS-2018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13082105#comment-13082105
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Jitendra Nath Pandey commented on HDFS-2018:
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A few comments:
getFirstTxnId and getLastTxnId seem a bit redundant in the EditLogInputStream
interface. The first txnid must be the last read plus one. The last txnid can
be obtained using getNumberOfTransactions.
Similarly in the constructor of EditLogFileInputStream. It might lead to
inconsistent use of EditLogFileInputStream, for example if the file contents
don't match the transaction ids being passed.
> what's the story on exclusive locking of journal managers after this? Do we
> still assume that they'll be locked by FSImage? Or should we push
> down locking to the journal managers as well?
I think JournalManagers should not be assumed to be locked by FSImage.
FSEditLog should manage the synchronization for JournalManagers where they
interact with namesystem.
> not sure I follow why getNumberOfTransactions throws a CorruptionException if
> you've asked for a transaction ID in the middle of a gap. Isn't
> it more consistent to just return 0? ie that journal just wasn't being
> written to for that txid?
Is it intended to distinguish between the cases when there is gap or if the
journal doesn't have any more transactions? It may be useful to distinguish
between the two, but I agree that CorruptionException is not very convincing,
because the journal is not really corrupt, it can still serve valid ranges of
transactions.
> 1073: Move all journal stream management code into one place
> ------------------------------------------------------------
>
> Key: HDFS-2018
> URL: https://issues.apache.org/jira/browse/HDFS-2018
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Ivan Kelly
> Assignee: Ivan Kelly
> Fix For: 0.23.0
>
> Attachments: HDFS-2018.diff, HDFS-2018.diff, HDFS-2018.diff,
> HDFS-2018.diff, HDFS-2018.diff, HDFS-2018.diff, HDFS-2018.diff,
> HDFS-2018.diff, HDFS-2018.diff, HDFS-2018.diff, HDFS-2018.diff,
> HDFS-2018.diff, HDFS-2018.diff, HDFS-2018.diff
>
>
> Currently in the HDFS-1073 branch, the code for creating output streams is in
> FileJournalManager and the code for input streams is in the inspectors. This
> change does a number of things.
> - Input and Output streams are now created by the JournalManager.
> - FSImageStorageInspectors now deals with URIs when referring to edit logs
> - Recovery of inprogress logs is performed by counting the number of
> transactions instead of looking at the length of the file.
> The patch for this applies on top of the HDFS-1073 branch + HDFS-2003 patch.
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