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https://issues.apache.org/jira/browse/BOOKKEEPER-552?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13626307#comment-13626307
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Jiannan Wang commented on BOOKKEEPER-552:
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{quote}
actually, migration is complicated thing as we discussed last year. but as my
understanding, if we want to proceed migration, at least we need to guarantee
the target ledger metadata would generate ledger ids with source ledger manager
in same ledger id space. so actually ledger id is an independent and critical
metadata rather ledger metadata itself. so I would suggest the ledger format
should be fixed during the life cycle of an instance.
{quote}
Agree.
{quote}
but NUM_SLOTS could not be changed only when we use NUM_SLOTS to partition
ledger metadata into different zookeeper ensembles. if this id generator is
used only in single ledger manager, it could be changed.
{quote}
Yes, you are right.
More specifically, on the ledger id generation, the critical thing is to make
sure ledger id is generated in incremental way, or it might cause issue: ledger
id that deleted before is possible to be reused again and if the ledger's
metadata is removed in metadata storage while ledger data not been cleaned in
bookie server then some of current logic is broken.
With this (incremental ledger id generation) in mind, change NUM_SLOTS is not a
big problem since there is retry logic for existing ledger id's case when
creating new ledger. However, I don't think user needs to care/modify this
setting.
> 64 Bits Ledger ID Generation
> ----------------------------
>
> Key: BOOKKEEPER-552
> URL: https://issues.apache.org/jira/browse/BOOKKEEPER-552
> Project: Bookkeeper
> Issue Type: Sub-task
> Components: bookkeeper-client, bookkeeper-server, hedwig-server
> Reporter: Jiannan Wang
> Assignee: Jiannan Wang
> Fix For: 4.3.0
>
> Attachments: BOOKKEEPER-552.patch, BOOKKEEPER-552.patch,
> BOOKKEEPER-552.patch
>
>
> This task aims to find and implement 64 bits global unique ledger id
> generation mechanisms.
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