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https://issues.apache.org/jira/browse/ZOOKEEPER-1001?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13009704#comment-13009704
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Flavio Junqueira commented on ZOOKEEPER-1001:
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In ZOOKEEPER-462, Utkarsh was not really in favor of having the BK client
updating ZK periodically, since he thought that it was a functionality that
should be implemented by the application. I avoided this direction mostly due
to those comments.
Now, discussing with Ivan earlier today, he gave a suggestion that I thought
was interesting. He suggested that we could treat the CLOSED znode as
checkpoint (and perhaps rename it) instead of updating it only at the end. That
is, we could have a call that is something like "checkpoint but keep open",
which essentially updates the CLOSED znode with the last committed operation,
but it does not represent the end of the ledger. The application could update
it as often as it wants.
How do you feel about this approach?
> Read from open ledger
> ---------------------
>
> Key: ZOOKEEPER-1001
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1001
> Project: ZooKeeper
> Issue Type: New Feature
> Components: contrib-bookkeeper
> Reporter: Flavio Junqueira
> Attachments: zk-1001-design-doc.pdf, zk-1001-design-doc.pdf
>
>
> The BookKeeper client currently does not allow a client to read from an open
> ledger. That is, if the creator of a ledger is still writing to it (and the
> ledger is not closed), then an attempt to open the same ledger for reading
> will execute the code to recover the ledger, assuming that the ledger has not
> been correctly closed.
> It seems that there are applications that do require the ability to read from
> a ledger while it is being written to, and the main goal of this jira is to
> discuss possible implementations of this feature.
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