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https://issues.apache.org/jira/browse/BOOKKEEPER-455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13490536#comment-13490536
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Sijie Guo commented on BOOKKEEPER-455:
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{quote}
Suppose bookie persist entry 1, 3, 4, and entry 2 failed and being retried (TCP
handles IP layer package lost), and now bookie crash.
If the ledger is recovered, last-confirmed-entry-id can be set to 4. When
readers try to read 2, it will not get it.
{quote}
some explanations about LAC.
during initialization, -1 is LAC.
case1:
1) adding 0 : sending 0 with (LAC=-1)
2) acked 0 : LAC changed from -1 to 0
3) adding 1 : sending 1 with (LAC=0)
4) acked 1 : LAC changed from 0 to 1
case2:
1) adding 0, 1, 2, 3, 4 : sending 0, 1, 2, 3, 4 with (LAC=-1)
2) acked 0: LAC changed from -1 to 0
3) acked 1: LAC changed from 0 to 1
4) failed to add 2.
in this case, LAC is -1 since the hint stored with 0~4 are -1. and LAC would
not be larger than the entry that isn't ACKed.
> Bookie recovery made assumption that entries are persisted in entry id order
> ----------------------------------------------------------------------------
>
> Key: BOOKKEEPER-455
> URL: https://issues.apache.org/jira/browse/BOOKKEEPER-455
> Project: Bookkeeper
> Issue Type: Bug
> Components: bookkeeper-server
> Affects Versions: 4.2.0
> Reporter: Yixue (Andrew) Zhu
> Priority: Minor
>
> The entries sent by bookkeeper client can be out of order (due to network).
> The client uses queue to track last-confirmed-entry-id correctly.
> The bookie server will happily persist the entries out of order, i.e. gaps
> are possible. If bookie crash, the recovery can cause last-confirmed-entry-id
> to be set to the last-entry persisted by bookie. The gap is not tracked nor
> detected at server side.
>
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