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From Amit Mittal <amitmitt...@gmail.com>
Subject Re: DistributedCache deprecated
Date Thu, 30 Jan 2014 12:27:09 GMT
Hi Prav,

Yes, you are correct that DistributedCache does not upload file into
memory. Also using job configuration and DistributedCache are 2 different
approaches. I am referring based on "Hadoop: The definitive guide"
Chapter:8 > Side Data Distribution (Page 288-295).
As you are saying that now methods of DistributedCache moved to Job, I
request if you please share some article or document on that for my better
understanding, it will be great help.

Thanks
Amit


On Thu, Jan 30, 2014 at 5:35 PM, praveenesh kumar <praveenesh@gmail.com>wrote:

> Hi Amit,
>
> I am not sure how are they linked with DistributedCache.. Job
> configuration is not uploading any data in memory.. As far as I am aware of
> how DistributedCache works, nothing get loaded in memory. Distributed cache
> just copies the files into slave nodes, so that they are accessible to
> mappers/reducers. Usually the location is
> ${hadoop.tmp.dir}/${mapred.local.dir}/tasktracker/archive (depends from
> distribution to distribution) You always have to read the files in your
> mapper or reducer when ever you want to use them.
>
> What has happened is the method of DistributedCache class has now been
> added to Job class, and I am assuming they won't change the functionality
> of how distributed cache methods used to work, otherwise there would have
> been some nice articles on that, plus I don't see any reason of changing
> that as well too..  so everything works still the same way.. Its just that
> you use the new Job class to use distributed cache features.
>
> I am not sure what entries you are exactly pointing to. Am I missing
> anything here ?
>
>
> Regards
> Prav
>
>
> On Thu, Jan 30, 2014 at 6:12 AM, Amit Mittal <amitmittal5@gmail.com>wrote:
>
>> Hi Mike & Prav,
>>
>> Although I am new to Hadoop, but would like to add my 2 cents if that
>> helps.
>> We are having 2 ways for distribution of shared data, one is using Job
>> configuration and other is DistributedCache.
>> As job configuration is read by the JT, TT and child JVMs, and each time
>> the configuration is read, all of its entries are read in memory, even if
>> they are not used. So using job configuration is not advised if the data is
>> more than few kilobytes. So it is not alternative to DistributedCache
>> unless some modifications are done in Job configuration to address this
>> limitation.
>> So I am also curious to know the alternatative to DistributedCache class.
>>
>> Thanks
>> Amit
>>
>>
>>
>> On Thu, Jan 30, 2014 at 2:43 AM, Giordano, Michael <
>> Michael.Giordano@vistronix.com> wrote:
>>
>>>  I noticed that in Hadoop 2.2.0
>>> org.apache.hadoop.mapreduce.filecache.DistributedCache has been deprecated.
>>>
>>>
>>>
>>> (http://hadoop.apache.org/docs/current/api/deprecated-list.html#class)
>>>
>>>
>>>
>>> Is there a class that provides equivalent functionality? My application
>>> relies heavily on DistributedCache.
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Mike G.
>>>
>>> This communication, along with its attachments, is considered
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>>> of the person(s) named above.  Note that unauthorized disclosure or
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>>>
>>
>>
>

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