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From Cee Tee <c.turks...@gmail.com>
Subject Re: About ZooKeeper Dynamic Reconfiguration
Date Wed, 21 Aug 2019 14:55:04 GMT
We have solved this by implementing a 'zookeeper cluster balancer', it 
calls the admin server api of each zookeeper to get the current status and 
will issue dynamic reconfigure commands to change dead servers into 
observers so the quorum is not in danger. Once the dead servers reconnect, 
they take the observer role and are then reconfigured into participants again.

Added benefit is that we can also control which data center gets the quorum 
in case of a network outage between the two.
Regards
Chris

On 21 August 2019 16:42:37 Alexander Shraer <shralex@gmail.com> wrote:

> Hi,
>
> Reconfiguration, as implemented, is not automatic. In your case, when
> failures happen, this doesn't change the ensemble membership.
> When 2 of 5 fail, this is still a minority, so everything should work
> normally, you just won't be able to handle an additional failure. If you'd
> like
> to remove them from the ensemble, you need to issue an explicit
> reconfiguration command to do so.
>
> Please see details in the manual:
> https://zookeeper.apache.org/doc/r3.5.5/zookeeperReconfig.html
>
> Alex
>
> On Wed, Aug 21, 2019 at 7:29 AM Gao,Wei <Wei.Gao@arcserve.com> wrote:
>
>> Hi
>>    I encounter a problem which blocks my development of load balance using
>> ZooKeeper 3.5.5.
>>    Actually, I have a ZooKeeper cluster which comprises of five zk
>> servers. And the dynamic configuration file is as follows:
>>
>>   server.1=zk1:2888:3888:participant;0.0.0.0:2181
>>   server.2=zk2:2888:3888:participant;0.0.0.0:2181
>>   server.3=zk3:2888:3888:participant;0.0.0.0:2181
>>   server.4=zk4:2888:3888:participant;0.0.0.0:2181
>>   server.5=zk5:2888:3888:participant;0.0.0.0:2181
>>
>>   The zk cluster can work fine if every member works normally. However, if
>> say two of them are suddenly down without previously being notified,
>> the dynamic configuration file shown above will not be synchronized
>> dynamically, which leads to the zk cluster fail to work normally.
>>   I think this is a very common case which may happen at any time. If so,
>> how can we resolve it?
>>   Really look forward to hearing from you!
>> Thanks
>>




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