[jira] [Commented] (BOOKKEEPER-447) Bookie can fail to recover if index pages flushed before ledger flush acknowledged

["Sijie Guo (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/BOOKKEEPER-447?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13486788#comment-13486788 ] 

Sijie Guo commented on BOOKKEEPER-447:
--------------------------------------

{quote}
Bookie index page steal (LedgerCacheImpl::grabCleanPage) can cause index file to reflect unacknowledged entries (due to flushLedger). Suppose ledger and entry fail to flush due to Bookkeeper server crash, it will cause ledger recovery not able to use the bookie afterward, due to InterleavedStorageLedger::getEntry throws IOException.
{quote}

If failed to flush entry log, the last mark will not be rolled. so the entries are still in journal, they would be replayed and added to new entry log files and update the ledger index. I assumed that it should not throw IOException when getEntry. Could you describe more about the case? is it easy to reproduce that?
                
> Bookie can fail to recover if index pages flushed before ledger flush acknowledged
> ----------------------------------------------------------------------------------
>
>                 Key: BOOKKEEPER-447
>                 URL: https://issues.apache.org/jira/browse/BOOKKEEPER-447
>             Project: Bookkeeper
>          Issue Type: Bug
>          Components: bookkeeper-server
>    Affects Versions: 4.2.0
>            Reporter: Yixue (Andrew) Zhu
>            Assignee: Robin Dhamankar
>              Labels: patch
>             Fix For: 4.2.0
>
>
> Bookie index page steal (LedgerCacheImpl::grabCleanPage) can cause index file to reflect unacknowledged entries (due to flushLedger). Suppose ledger and entry fail to flush due to Bookkeeper server crash, it will cause ledger recovery not able to use the bookie afterward, due to InterleavedStorageLedger::getEntry throws IOException.
> If the ackSet bookies all experience this problem (DC environment), the ledger will not be able to recover.
> The problem here essentially a violation of WAL. One reasonable fix is to track ledger flush progress (either per-ledger entry, or per-topic message). Do not flush index pages which tracks entries whose ledger (log) has not been flushed.

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