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From Ivan Kelly <i...@ivankelly.net>
Subject Re: Does zookeeper guarantee read your write in consecutive sessions?
Date Sat, 15 Nov 2014 09:21:57 GMT
I'm not 100% sure, but i think session creation creates a znode
(session info is definitely passed around the quorum). Since it has to
create a znode, it will not response to the client until it sees the
znode has been created, which means it is up to date with the leader
until at least that point, so it will be able to see any updates from
the previous session.


On 14 November 2014 03:42, bit1129@163.com <bit1129@163.com> wrote:
> Hi,
> Consider the following scenario:
> ABCDE is the zookeeper ensemble,  ABC form the quorum.
> The following sequence may happen:
> 1. Client writes the data, and ABC are updated, but DE haven't because of the network
latency(say, long enough for this scenario).
> 2. Client closes the session.
> 3. Client start a new session in the same thread, Is zookeeper guarantee the client to
see the previously data set in the above step(that is,  it will connect to A, B or C) or zookeeper
does NOT guarantee this(that is,it may connect to D or E which doesn't have the data set in
above steps)
> I guess that Zookeeper doesn't guarantee  the client to see the data set in the first
step  because the two sessions are totally different ones to Zookeeper even they are created
by the same thread, and also because when the session is first created, there is no zxid information
that the server can be used to determine the client status.
> Please correct me if I am wrong, thanks.
> bit1129@163.com

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