On 05/19/2010 01:23 PM, Flavio Junqueira wrote:
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.

Hi Flavio. Seems like wrapping up a couple/few of these options in the client library (or "a" client library) would be useful for users -- reuse rather than everyone reinvent. Similar to how we now provide recipes in zk source base rather than everyone rewriting the basic locks/queues... Would be a great project I would think for someone interested in getting started with bk (and to some extent zk) development.


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.


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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