[jira] [Commented] (BOOKKEEPER-455) Bookie recovery made assumption that entries are persisted in entry id order

["Flavio Junqueira (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/BOOKKEEPER-455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13490272#comment-13490272 ] 

Flavio Junqueira commented on BOOKKEEPER-455:
---------------------------------------------

Hi Andrew, There are a couple of things I'd like to clarify here. We use TCP, so I would expect requests to be delivered to each bookie in order, even if there are packet drops, retransmissions, and such. Now even if the entries are delivered out of order, using an older last-add-confirmed value (LAC) does not hurt correctness. The LAC value is just a hint. But, it is correct that getting a LAC value closer to the last confirmed will speed up recovery. 
                
> 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
>
> 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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