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https://issues.apache.org/jira/browse/BOOKKEEPER-447?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13487052#comment-13487052
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Robin Dhamankar commented on BOOKKEEPER-447:
--------------------------------------------
Since in the common case the journal would have been flushed before index
entries are written out, it is better to follow the approach of tracking what
has been flushed and if it hasn't (in the uncommon case) then waiting for it to
be flushed.
> 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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