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From Mahadev Konar <maha...@yahoo-inc.com>
Subject Re: Some questions about Zookeeper 3.2.0
Date Tue, 30 Jun 2009 16:14:58 GMT
Hi Qian,
 Sorry for the delayed response. ZooKeeper guarantees that their is
backwards compatibility with minor releases. So, 3.2* is backwards
compatible with 3.1*. So, what Ted mentions below related to rolling upgrade
should work. 

Hope this helps.

Ted Dunning:

A rolling update works very well for that.  You can also change the number
of nodes in the cluster.

To do this, you replace the config files on the surviving servers and on the
new server.

Then take down the one that is leaving the cluster and then one by one
restart the servers that will remain in the cluster.  Then start the new

If you only have 3 ZK servers, you might want to do the upgrade in two steps
if you are totally paranoid about running with just 2 servers in your
cluster.  In that scenario, you would add the new server to the config and
restart each of the 3 ZK servers and staring the new one.  That gives you a
ZK cluster with 4 servers.  Another rolling update can reconfigure it to
have only the 3 servers you want.

Make sure you leave several seconds between restarting each server.  That
will give the cluster time to calm down and do any necessary leader

On 6/28/09 11:03 PM, "Qian Ye" <yeqian.zju@gmail.com> wrote:

> A related question.  If I have run a Zookeeper service with many ephemeral
> znodes on five servers, then I want to replace one of the servers by a new
> one, and the new server has a new IP. How can I do the job without any loss
> of data ?
> Thanks
> On Mon, Jun 29, 2009 at 9:24 AM, Qian Ye <yeqian.zju@gmail.com> wrote:
>> Thanks for the explanation, it sounds great.
>> It seems that I should study more on Zookeeper :-)
>> regards
>> On Mon, Jun 29, 2009 at 2:15 AM, Ted Dunning <ted.dunning@gmail.com>wrote:
>>> I don't think you should be very nervous at all.
>>> There are two questions:
>>> 1) can 3.1.1 go to 3.2 with no down time.  This is very likely, but a
>>> wiser
>>> head than mine should have final say
>>> 2) can 3.1.1 go to 3.2 with < 1 minute of downtime.  The is for sure.
>>> Neither option involves data loss.
>>> ZK is actually really really good for HA operations.
>>> On Sun, Jun 28, 2009 at 4:55 AM, Qian Ye <yeqian.zju@gmail.com> wrote:
>>>> your answer makes me nervous about upgrade Zookeeper
>>>> server
>> --
>> With Regards!
>> Ye, Qian
>> Made in Zhejiang University

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