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From Yogi Devendra <yogideven...@apache.org>
Subject Re: HDFS File Reader Module
Date Tue, 23 Feb 2016 12:56:36 GMT
Priyanka,

Thanks for the update. I will consider these ports during the design phase
of my proposal for HDFS file copy module.

I believe you are planning to add this to Apex Malhar. Please post any link
/ private branch (if any) where I can have a look at the first cut.

I will ask for your help if I come across any questions, uncertainties etc.

~ Yogi

On 23 February 2016 at 17:59, Priyanka Gugale <priyanka@datatorrent.com>
wrote:

> I am planning to have following ports to this module:
>
> Ports
> Input port: None
>
> Output port:
>
>    1. FileMetadata
>    2. BlockMetadata
>    3. Block bytes
>
> -Priyanka
>
> On Tue, Feb 23, 2016 at 2:16 PM, Yogi Devendra <yogidevendra@apache.org>
> wrote:
>
> > 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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