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https://issues.apache.org/jira/browse/ZOOKEEPER-462?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12763595#action_12763595
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Utkarsh Srivastava commented on ZOOKEEPER-462:
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Ben and I discussed this and we dont think this is the best design. Under the
current design, a lot of unnecessary write load will be put on ZK.
Instead, the bookies already support a method to query for the last entry for a
particular ledger. Thus, a client that wants to read an unclosed ledger can ask
the bookies for their last entries and read until there.
> Last hint for open ledger
> -------------------------
>
> Key: ZOOKEEPER-462
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-462
> Project: Zookeeper
> Issue Type: New Feature
> Components: contrib-bookkeeper
> Reporter: Flavio Paiva Junqueira
> Assignee: Flavio Paiva Junqueira
> Fix For: 3.3.0
>
> Attachments: ZOOKEEPER-462.patch
>
>
> In some use cases of BookKeeper, it is useful to be able to read from a
> ledger before closing the ledger. To enable such a feature, the writer has to
> be able to communicate to a reader how many entries it has been able to write
> successfully. The main idea of this jira is to continuously update a znode
> with the number of successful writes, and a reader can, for example, watch
> the node for changes.
> I was thinking of having a configuration parameter to state how often a
> writer should update the hint on ZooKeeper (e.g., every 1000 requests, every
> 10,000 requests). Clearly updating more often increases the overhead of
> writing to ZooKeeper, although the impact on the performance of writes to
> BookKeeper should be minimal given that we make an asynchronous call to
> update the hint.
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