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Zookeeper >> mail # user >> Rolling upgrades


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Re: Rolling upgrades
Any even number that is greater than half of the configured number of nodes
is fine.

The only *really* bad even number of servers is 0.

On Thu, Mar 8, 2012 at 4:24 PM, Ted Dunning <[EMAIL PROTECTED]> wrote:

> 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 <[EMAIL PROTECTED]>wrote:
>
>> AlsoŠ
>>
>> 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" <[EMAIL PROTECTED]> 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:[EMAIL PROTECTED]]
>> >> Sent: Thursday, March 08, 2012 3:31 PM
>> >> To: [EMAIL PROTECTED]
>> >> 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
>> >
>> >
>>
>>
>