[infinispan-dev] MapReduce limitations and suggestions.

[Vladimir Blagojevic]

Tristan,

Actually they are not addressed in this pull request but the feature 
where custom output cache is used instead of results being returned is 
next in the implementation pipeline.

Evangelos, indeed, depending on a reducer function all intermediate 
KOut/VOut pairs might be moved to a single node. How would custom cache 
help in this case?

Regards,
Vladimir


On 2/14/2014, 10:16 AM, Tristan Tarrant wrote:
> Hi Evangelos,
>
> you might be interested in looking into a current pull request which
> addresses some (all?) of these issues
>
> https://github.com/infinispan/infinispan/pull/2300
>
> Tristan
>
> On 14/02/2014 16:10, Evangelos Vazaios wrote:
>> Hello everyone,
>>
>> I started using the MapReduce implementation of Infinispan and I came
>> across some possible limitations. Thus,  I want to make some suggestions
>> about the MapReduce (MR) implementation of Infinispan.
>> Depending on the algorithm,  there might be some memory problems,
>> especially for intermediate results.
>> An example of such a case is  group by. Suppose that we have a cluster
>> of 2 nodes with 2 GB  available. Let a distributed cache, where simple
>> car objects (id,brand,colour) are stored and the total size of data is
>> 3.5GB. If all objects have the same colour , then all 3.5 GB would go to
>> only one reducer, as a result an OutOfMemoryException will be thrown.
>>
>> To overcome these limitations, I propose to add as parameter the name of
>> the intermediate cache to be used. This will enable the creation of a
>> custom configured cache that deals with the memory limitations.
>>
>> Another feature that I would like to have is to set the name of the
>> output cache. The reasoning behind this is similar to the one mentioned
>> above.
>>
>> I wait for your thoughts on these two suggestions.
>>
>> Regards,
>> Evangelos
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>>
>>
>
>
>
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