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From Ted Dunning <ted.dunn...@gmail.com>
Subject Re: Rolling upgrades
Date Fri, 09 Mar 2012 00:24:48 GMT
It won't be any different than a temporary state when one of 3 or 5 nodes
is down.

On Thu, Mar 8, 2012 at 4:10 PM, Jordan Zimmerman <jzimmerman@netflix.com>wrote:

> Also҆
>
> I thought that ZK ensembles need to be odd in number. How would ZK handle
> a temporary state where there is an even number?
>
> -JZ
>
> On 3/8/12 3:39 PM, "Alexander Shraer" <shralex@yahoo-inc.com> wrote:
>
> >I don't think there is a problem if you do it as you say, or even if you
> >just change the config files of all servers at once and restart them,
> >because a majority of the new config
> >necessarily intersects with a majority of the old one, so a server who
> >has the latest state will be elected leader.
> >
> >Alex
> >
> >> -----Original Message-----
> >> From: Jordan Zimmerman [mailto:jzimmerman@netflix.com]
> >> Sent: Thursday, March 08, 2012 3:31 PM
> >> To: user@zookeeper.apache.org
> >> Subject: Rolling upgrades
> >>
> >> I've been reading the archives regarding rolling upgrades. Here's the
> >> scenario, given a stable ensemble:
> >>
> >> ZK1 <-> ZK2 <-> ZK3
> >>
> >> In the above, the zoo.cfg for each server looks like this (pseudo):
> >> server.1=ZK1
> >> server.2=ZK2
> >> server.3=ZK3
> >>
> >> I want to add a new server, ZK4. If I understand this correctly, I'd
> >> bring up ZK4 with this config:
> >> server.1=ZK1
> >> server.2=ZK2
> >> server.3=ZK3
> >> server.4=ZK4
> >>
> >> At this point, though, the configs don't match in the ensemble. How do
> >> the ZK instances handle this?
> >>
> >> Continuing...
> >>
> >> Once ZK4 is up, ZK1 would get the new config and get restarted. Once
> >> ZK1 is up, ZK2 gets new config, etc.
> >>
> >> At each point of config change, the cluster is in a confused state
> >> about the config. Is there code in ZK to handle this?
> >>
> >> -JZ
> >
> >
>
>

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