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https://issues.apache.org/jira/browse/ZOOKEEPER-1001?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13014944#comment-13014944
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dhruba borthakur commented on ZOOKEEPER-1001:
---------------------------------------------

On a related question: is the writing of a ledger entry atomic (for a single 
bookie)? For example, if an application writes a ledger entry to a certain 
bookie and a concurrent reader tries to read that entry (even if that entry is 
not committed to all bookies), is it possible that only a part of that ledger 
entry is visible to the reader?

> 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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