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Zookeeper >> mail # user >> Sync question


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Re: Sync question
The guarantee when using "sync + read" and updates is that the read
will see any update that completes before the sync starts (if the
update starts after the sync it is concurrent and may be reordered
even with ACID). ZooKeeper guarantees much more than eventual
consistency... if you're using sync it guarantees linearizability
between "sync + read" pairs and updates.

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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> Deutsche Bank does not render legal or tax advice, and the information contained in this communication should not be regarded as such.
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB