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From Yogi Devendra <yogideven...@apache.org>
Subject Re: HDFS File Reader Module
Date Tue, 23 Feb 2016 08:46:14 GMT
Priyanka,

Can you please share details about what would be the output ports from this
module?

I am thinking of HDFS File Copy Module which can be used in conjunction
with this module to copy files from HDFS to HDFS.

~ Yogi

On 18 February 2016 at 10:29, Mohit Jotwani <mohit@datatorrent.com> wrote:

> +1 to add this.
>
> Regards,
> Mohit
> On 17 Feb 2016 23:30, "Pramod Immaneni" <pramod@datatorrent.com> wrote:
>
> > +1 to add this module
> >
> > On Wed, Feb 17, 2016 at 9:21 AM, Priyanka Gugale <
> priyanka@datatorrent.com
> > >
> > wrote:
> >
> > > We need partitions for parallel read but how will the reader partition
> > know
> > > which offset of the file it should read from. Normally FileSplitter
> > creates
> > > this metadata, let's call them as reader task, and forwards them to
> next
> > > operator which is block reader. Block reader will receive one of the
> > tasks
> > > and read from specified offset in file. If FileSplitter is absent one
> > > reader partition will have to consume one file entirely, which means we
> > > can't have parallel reading over one file. I hope this answers your
> > > question.
> > >
> > > Advantage of having this module is having a reusable component made up
> of
> > > operators which are frequently used together to do file reading.
> > >
> > > -Priyanka
> > >
> > > On Wed, Feb 17, 2016 at 11:31 AM, Yogi Devendra <
> yogidevendra@apache.org
> > >
> > > wrote:
> > >
> > > > Let me rephrase Ram's question to make it clear:
> > > >
> > > > For an application developer using Malhar:
> > > > What are the advantages / disadvantages of using the proposed HDFS
> File
> > > > input Module as compared to directly using FileSplitter, BlockReader
> > > > Operators available in Malhar?
> > > >
> > > > ~ Yogi
> > > >
> > > > On 16 February 2016 at 21:56, Munagala Ramanath <ram@datatorrent.com
> >
> > > > wrote:
> > > >
> > > > > Can parallel read not be achieved by partitioning ?
> > > > >
> > > > > Ram
> > > > >
> > > > > On Tue, Feb 16, 2016 at 1:01 AM, Priyanka Gugale <
> > > > priyanka@datatorrent.com
> > > > > >
> > > > > wrote:
> > > > >
> > > > > > Hi,
> > > > > >
> > > > > > It is a common usecase to read big files on HDFS in parallel
> > fashion
> > > > i.e.
> > > > > > many reader thread are used to read the file in parallel. We
can
> > > > achieve
> > > > > > this on top of Apex using following Malhar operators:
> > > > > >
> > > > > > 1. AbstractFileSplitter
> > > > > > 2. AbstractBlockReader
> > > > > >
> > > > > > where FileSplitter, as per file metadata, creates small reader
> > > tasks(to
> > > > > > read file in parts). Those reader tasks are run by BlockReaders
> in
> > > > > parallel
> > > > > > to read the file.
> > > > > >
> > > > > > As these operators are generally used together to achieve file
> read
> > > > > > operation, I propose we create a module, called HDFSFileReader
> for
> > > > this.
> > > > > >
> > > > > > Please provide your suggestions on same.
> > > > > >
> > > > > > -Priyanka
> > > > > >
> > > > >
> > > >
> > >
> >
>

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