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Date: Tue, 14 Jul 2009 14:15:13 -0700
From: Patrick Hunt <phunt@apache.org>
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To: zookeeper-user@hadoop.apache.org
Subject: Re: Instantiating HashSet for DataNode?
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Erik, if you'd like enter a JIRA and take a whack at it go ahead. 
Perhaps a subclass of DataNode specific for ephemerals? That way it can 
handle any particulars - and should also minimize the number of 
"if(children==null)" type checks that would be needed. (don't neg. 
impact performance or b/w compat though). You would probably learn more 
about zk internals, testing, etc... in the process.

http://wiki.apache.org/hadoop/ZooKeeper/HowToContribute

Patrick

Mahadev Konar wrote:
> Hi Erik,
>   I am not sure if that would a considerable opitmization but even if you
> wanted to do it, it would be much more than just adding a check in the
> constructor (the serialization/deserialization would need to have
> specialized code). Right now all the datanodes are treated equally for
> ser/derser and other purposes.
> 
> 
> mahadev
> 
> 
> 
> 
> On 7/14/09 1:42 PM, "Erik Holstad" <erikholstad@gmail.com> wrote:
> 
>> I'm not sure if I've miss read the code for the DataNode, but to me it looks
>> like every node gets a set of children even though it might be an
>> ephemeral node which cannot have children, so we are wasting 240 B for every
>> one of those. Not sure if it makes a big difference, but just thinking
>> that since everything sits in memory and there is no reason to instantiate
>> it, maybe it would be possible just to add a check in the constructor?
>>
>> Regards Erik
>