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From Mark <static.void....@gmail.com>
Subject Re: Design question
Date Wed, 09 Nov 2011 15:29:11 GMT
Memory constraints of those machines prevent us from being able to load 
two models at the same time.

On 11/8/11 10:10 PM, Ted Dunning wrote:
> Yes.  This definitely could be done with ZK.
>
> See chapter 16 of Mahout in Action for an example of how to manage this for
> a farm of classifiers which have very similar issues (although loading a
> new model is much faster).
>
> One trick that might work is to load the new model before dropping the old
> one.  You might be able to do a very fast handover that way.
>
> On Tue, Nov 8, 2011 at 12:18 PM, Mark<static.void.dev@gmail.com>  wrote:
>
>> I have a general design question regarding ZooKeeper.
>>
>> Our use case: We currently have 3 restful recommendation servers that
>> simply wrap a Mahout GenericBooleanPrefItemBasedRec**ommender. We started
>> off using a JDBCDataModel but for performance reasons we had to switch to a
>> FileDataModel so everything would be kept in memory. Although now that our
>> recommendations service is blazing fast the start up/reloading time for
>> each of these services are in the minutes. If we try to update all services
>> at once then all recommendation requests come to a halt. As a result of
>> this whenever we push a new model we have to do it in stages... ie disable
>> server1, update, wait, renable, disable server2.... We've "automated" this
>> using cron by simply updating one server waiting 10 mins then updating the
>> next and so on. We are trying to figure out if this coordination would be
>> better managed via ZooKeeper.
>>
>> I've read a bit into ZooKeeper and it seems like it would be easy to set a
>> watch on a node to trigger when a model has changed thus triggering a
>> refresh of our recommender. Where I get lost is how would I coordinate this
>> so only one server at a time goes down? When it comes back up then the next
>> server should be updated. Can someone please explain how this could be
>> accomplished? Thanks
>>

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