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Re: Sync question
the read will be up to date with respect to the sync: the data you read is
guaranteed to reflect at least the state of the system when the sync
executed. even if you only have one server, so it is always perfectly
up-to-date, you can do a read and the server will return the latest value,
but by the time the network packet gets to you an update could have
happened at the leader such that you are up-to-date.
the same thing happens with writes as well: you do a write, but by the time
you get the response another client may have updated your value.

if you want to get something stronger, you can surround your reads and
writes with a lock znode that must be acquired and released by clients when
reading or writing the data. this will be a large overhead for very little
gain though.

ben
On Tue, Nov 5, 2013 at 11:38 AM, Adrian Osullivan
<[EMAIL PROTECTED]>wrote:

> Thanks, just wanted to confirm that. Some of the things you read about
> sync seem to suggest the next client read will be up to date but this is
> not strictly true.  This isn't a fault of course, but by design.
>
> -----Original Message-----
> From: Jordan Zimmerman [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, November 05, 2013 2:36 PM
> To: [EMAIL PROTECTED]
> Subject: Re: Sync question
>
> > So it seems there is no mechanism is zookeeper for guaranteeing a read
> is truly up to date with the leader. Is this true?
>
> ZooKeeper is an eventually consistent system, not an ACID system. So, true.
>
> On Nov 5, 2013, at 11:31 AM, Adrian Osullivan <[EMAIL PROTECTED]>
> wrote:
>
> > Hi everyone!  The zk API's sync() method brings the server up to date
> with the leader.  So the next client read should give the up to date value.
>  But in the time between completing the sync and starting the read, another
> client may have sent an update and the server one is connected to may again
> lag the leader.  So it seems there is no mechanism is zookeeper for
> guaranteeing a read is truly up to date with the leader. Is this true?
> >
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