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Zookeeper >> mail # dev >> question about BookKeeper Ledgers


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Re: question about BookKeeper Ledgers
Hi Dhruba, Ledgers are not named by the application currently. We  
simply assign an increasing identification number to a new ledger.  
Consequently, it is not possible to ask BK if ledger "foo" exists.

I don't think it would be difficult to add this feature, though. We  
keep the ledger metadata on ZooKeeper, and we can simply name the  
corresponding znodes  using the alias the application provides. In  
fact, one option would be to implement this alias scheme directly on  
the application using the same ZooKeeper installation.

Regarding the size of a ledger, we keep the entry count, but not the  
byte count currently. This is also an interesting feature we could  
consider adding.

Cheers,
-Flavio

On Dec 17, 2010, at 7:44 AM, Dhruba Borthakur wrote:

> Hi folks,
>
> I have a few questions about BookKeeper APIs:
>
> 1. is there a way to atomically check and create a ledger, something  
> similar
> to to the POSIX O_CREAT flag? I would like to create a ledger only  
> if the
> ledger does not already exist. If it exists, then the createLedger  
> call
> should fail. Is there a way to achieve this functionality?
> 2. Is there a way to find the current size of a ledger?
>
> thanks,
> dhruba
> --
> Connect to me at http://www.facebook.com/dhruba

flavio
junqueira

research scientist

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