If you do leader election with ZooKeeper, you basically have to try to create 
have to follow the instructions in this recipe: 
http://zookeeper.apache.org/doc/trunk/recipes.html#sc_leaderElection -- this 
involves creating an ephemeral+sequential node, and listening for changes to 
the nodes that precede yours.

If you do leader election in Helix, you configure your resource and 
participants up front, and then you're told by callback when you're leader, and 
you're told by callback when you've given up leadership. If you have multiple 
different logical entities that must have leaders, you can model this by just 
adding another partition to a resource. It's less error-prone this way, but you 
do need to spend extra time bringing up Helix controllers.
________________________________
> Date: Sat, 29 Mar 2014 23:05:46 +0200 
> Subject: Fwd: Re: Comparison question 
> From: [email protected] 
> To: [email protected] 
> 
> 
>>> Hello Masters, 
>> 
>>> We had some internal discussion regarding the comparison among 
> Helix and Zookeeper in term of leader election mechanism. 
>>> 
>>> I'd appreciate if you could elaborate in several points about the 
> benefit of Helix against the ZooKeeper in term of Leader Election 
> mechanism. What can I do in Helix that is missing in ZooKeeprt in term 
> of Leader Election. 
>>> 
>>> Thanks in advance, 
> Erwin 
>> 
> 
> ---------- Forwarded message ---------- 
> From: "Erwin Karbasi" <[email protected]<mailto:[email protected]>> 
> Date: Mar 30, 2014 12:02 AM 
> Subject: Re: Comparison question 
> To: "kishore g" <[email protected]<mailto:[email protected]>>, 
> <[email protected]<mailto:[email protected]>>
>  
> Cc: 
> 
> 
>> Hello Masters, 
> 
>> We had some internal discussion regarding the comparison among Helix 
> and Zookeeper in term of leader election mechanism. 
>> 
>> I'd appreciate if you could elaborate in several points about the 
> benefit of Helix against the ZooKeeper in term of Leader Election 
> mechanism. What can I do in Helix that is missing in ZooKeeprt in term 
> of Leader Election. 
>> 
>> Thanks in advance, 
>> Erwin 
                                          

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