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From Flavio Junqueira <...@yahoo-inc.com>
Subject Re: Concurrent reads and writes on BookKeeper
Date Wed, 19 May 2010 20:23:01 GMT
Hi Andre, To guarantee that two clients that read from a ledger will  
read the same sequence of entries, we need to make sure that there is  
agreement on the end of the sequence. A client is still able to read  
from an open ledger, though. We have an open jira about informing  
clients of the progress of an open ledger (ZOOKEEPER-462), but we  
haven't reached agreement on it yet. Some folks think that it is best  
that each application use the mechanism it finds best. One option is  
to have the writer writing periodically to a ZooKeeper znode to inform  
of its progress.

I would need to know more detail of your application before  
recommending you to stick with BookKeeper or switch to ZooKeeper. If  
your workload is dominated by writes, then BookKeeper might be a  
better option.

-Flavio

On May 19, 2010, at 1:29 AM, André Oriani wrote:

> Sorry, I forgot the subject on my last message :|
>
> Hi all,
> I was considering BookKeeper to implement some server replicated
> application having one primary server as writer and many backup  
> servers
> reading from BookKeeper concurrently. The last documentation a I had
> access says "This writer has to execute a close ledger operation  
> before
> any other client can read from it."  So readers cannot ready any  
> entry on
> the ledger, even the already committed ones until writer stops  
> writing to
> the ledger,i.e, closes it.  Is my understanding right ? Should I  
> then use
> Zookeeper directly to achieve what I want ?
>
>
> Thanks for the attention,
> André Oriani
>
>
>
>
>
>


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