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https://issues.apache.org/jira/browse/ZOOKEEPER-1016?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13008577#comment-13008577
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Mahadev konar commented on ZOOKEEPER-1016:
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Dhruba/Suresh,
I think the suggestion has been a little mis understood. Here is what I could
understand:
1) TeaKeeper will act as a T logger , wherein it will forward edit logs to
BookKeeper and BackUp NN.
2) On a BookKeeper edit log failure, TeaKeeper throws exception and Primary
fails or shuts down
3) On a BackUp edit log failure, TeaKepeer continues. The StanUp on coming up
will connect to primary and will start reading from where it left off.
I could be wrong and Ivan can correct me if I am but as Ivan mentioned earlier,
I think TeaKeeper would not be very useful if we can read Ledgers while they
are being written to.
> TeaKeeper: Hot standby support using bookkeeper
> -----------------------------------------------
>
> Key: ZOOKEEPER-1016
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1016
> Project: ZooKeeper
> Issue Type: Improvement
> Reporter: Ivan Kelly
> Assignee: Ivan Kelly
> Priority: Minor
> Attachments: tledger.pdf
>
>
> Currently Bookkeeper provides functionality for cold backups. If the entity
> logging to bookkeeper fails, its replacement must recover the ledgers which
> had been used for backup before becoming available. This is acceptable in
> some cases, such as HBase Wals where a small delay in recovery only results
> in a small percentage of data being unavailable.
> However, systems such as the HDFS namenode, this delay can be unacceptable,
> such as cases where data is being served to customers. Secondary namenodes
> should be ready to go the instant the primary goes down.
> TeaKeeper proposes a wrapper library around Bookkeeper providing T-Junction
> like functionality for logging. It also provides for primary/secondary
> election and automated hot failover.
> HDFS namenode is primary target of this work.
> The attached design doc contains more details.
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