Hi Jae, I wrote that article several years ago. (tbh - I hope it is not totally out of date by now). I agree with German's points.
The issue it was solving was to replace a bad server without having to shutdown the ensemble and without having to update the config files on each server. I would also add that this only works as long as the server names and ports are the same - iirc at the time the article was written we were using servers in AWS and referencing them either by assigned hostnames such as zookeeper-[01|11] or by elastic IP's that could be moved from server to server. If I understand your question correctly, if you are "adding a new server" such as going from 7 to 9 servers, then this approach won't benefit you as you. We also used this approach when we would upgrade the servers, but like German said we did it one server at a time so that the Leader election could be natural. This allowed us to upgrade a pool of 11 servers who were responsible for many thousands of client connections without any down time. Thanks Ben On 11/5/13 6:51 AM, "German Blanco" <[email protected]> wrote: >... and make sure that there is no rubbish in the data dir of the new >server. > > >On Tue, Nov 5, 2013 at 3:49 PM, German Blanco < >[email protected]> wrote: > >> Hello Jae, >> >> I think that the answer to your question is "no, there is no benefit in >>a >> rolling restart in that case". >> If you remove a machine that was hosting a zookeeper server that was >>part >> of a cluster, and replace it with a new machine, with a zookeeper server >> running the same software version and listening on the same IP and >>ports, >> then this new server will join the cluster, synchronize and start >>working >> normally. >> I wouldn't recommend to replace more than one server at a time, and I >> think that it is better if the new server joins while the existing >>quorum >> is stable (avoid leader elections while the new server joins, i.e. avoid >> restarts or disconnections of the existing servers). >> >> Best regards, >> >> Germán. >> >> >> On Tue, Nov 5, 2013 at 6:42 AM, Bae, Jae Hyeon <[email protected]> >>wrote: >> >>> Hi >>> >>> I read an article >>> >>> >>>http://www.benhallbenhall.com/2011/07/rolling-restart-in-apache-zookeepe >>>r-to-dynamically-add-servers-to-the-ensemble/ >>> >>> My question is, even though failed hardware is replaced with the same >>>IP >>> address, do I need to do rolling restart for adding replaced hardware >>>to >>> the quorum? >>> >>> I am using zookeeper ver3.4.5. >>> >>> Thank you >>> Best, Jae >>> >> >>
