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MapReduce, mail # user - InputFormat for some REST api


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Re: InputFormat for some REST api
Alex Thieme 2013-02-19, 19:48
Are there examples detailing how to write input formats, record readers and related classes? I was hoping to write one against a Redis database and it seems that shares similar issues to accessing data from a rest API.

Alex Thieme
[EMAIL PROTECTED]
508-361-2788
On Feb 19, 2013, at 1:34 PM, Robert Evans <[EMAIL PROTECTED]> wrote:

> I don't know of any input format that will do this out of the box.  But it should not be that hard to write one.  There are two big issues here.  
>
> the data you are reading form the API really needs to be static, or you could get some very odd inconsistencies. For example a node dies after a map task has finished and not all of the reducers got the data, so the map task is rerun and some of the reducers have some old data, and some of the reducers have new data.  This is the main reason to download the data before processing it.  You can work around this by using the input format to run a map only job that then writes the data out to a file before processing it the rest of the way.
> You need a good way to partition the data from the API.  This can be difficult unless the REST API provides a logical way to split this up.
> --Bobby
>
> From: Yaron Gonen <[EMAIL PROTECTED]>
> Reply-To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
> Date: Tuesday, February 19, 2013 4:49 AM
> To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
> Subject: InputFormat for some REST api
>
> Hi,
> Do you know of any InputFormat implemented for some REST api provider?
> Usually when one needs to process data that is accessible only by REST, one should try to download the data first someone, but what if you cannot download it?
>
> thanks