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https://issues.apache.org/jira/browse/ZOOKEEPER-1016?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13011756#comment-13011756
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Jitendra Nath Pandey commented on ZOOKEEPER-1016:
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  I have a couple of doubts about FileSystem as an abstraction for transaction 
logs:
 - Transaction logs don't need a hierarchical namespace. As I understand, 
transaction log is an ordered set (or sequence) of transaction records and the 
set needs a name.
 - Unit of data being read or written should be a transaction record and not a 
byte.

    
  




> 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, 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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