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From "Bae, Jae Hyeon" <metac...@gmail.com>
Subject Re: ZkClient bug can bring down broker/consumer on zookeeper push in EC2 environment
Date Tue, 16 Sep 2014 05:17:10 GMT
The above pull request didn't work perfectly. After a bunch of testing
experiment, we decided that fixing zkclient itself isn't easy. So we
decided to go with another workaround.

We're expecting zookeeper 3.5.0 will be stabilized as soon as possible with
the feature to refresh connections and the future version of kafka will
ship that zookeeper version.

On Mon, Sep 15, 2014 at 8:42 PM, Neha Narkhede <neha.narkhede@gmail.com>
wrote:

> Thanks for reporting this issue. Agree that this is a problem for Kafka
> users using AWS. Please can you open a JIRA so we can keep track of this?
>
> On Sun, Aug 17, 2014 at 11:41 AM, Bae, Jae Hyeon <metacret@gmail.com>
> wrote:
>
> > Recently, we found the serious ZkClient bug, actual Apache Zookeeper
> client
> > bug, which can bring down broker/consumer on zookeeper push.
> >
> > We're running kafka and zookeeeper in AWS EC2 environment. Zookeeper
> > instances are bound with EIP to give the static hostname for each
> instance,
> > which means even if the EC2 instance is terminated and replaced with the
> > new one, it will have the same hostname but its private IP bound to the
> > hostname can be changed.
> >
> > The scenario is, if we do rolling push all zookeeper server instances by
> > terminating and waiting until the new instance joins to the quorum one by
> > one, finally, ZkClient will try to connect to the old IP addresses which
> do
> > not exist any more due to DNS caching on Apache Zookeeper client side,
> > please refer to https://issues.apache.org/jira/browse/ZOOKEEPER-338
> >
> > So, we need to restart kafka brokers and consumers to refresh DNS cache.
> To
> > solve this problem, I sent the following pull request to ZkClient,
> > https://github.com/sgroschupf/zkclient/pull/26
> >
> > Please review the above PR. If new version of ZkClient with the following
> > fix is not released on the schedule of kafka 0.8.2 release, I'd like
> kafka
> > to ship the internally built ZkClient with the fix. I will really
> > appreciate.
> >
> > Thank you
> > Best, Jae
> >
>

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