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From Venkat Williams <venkat.willi...@gmail.com>
Subject Re: Create a CovertCSVToJSON Processor
Date Tue, 06 Jun 2017 13:52:54 GMT
Hi Joe Witt,

Thanks for your response.

I heard and read about about these record readers but not quite got it how
to use them using some test data or template. It will be great if you can
help me to get some working example or flow.

I want to know if these implementations support for RFC-4180
<https://tools.ietf.org/html/rfc4180> formatted CSV files and be sure to
handle edge cases like embedded newlines in a field value and escaped
double quotes.

Thanks for your help advance.

Regards,
Venkat

On Tue, Jun 6, 2017 at 7:07 PM, Joe Witt <joe.witt@gmail.com> wrote:

> Venkat
>
> I think you'll want to take a closer look at the apache nifi 1.2.0
> release support for record readers and record writers.  It handles
> schema aware parsing/transformation and more for things like csv,
> json, avro, can be easily extended, and supports scripted readers and
> writers written right there through the UI.  As it is new examples are
> still emerging but we can certainly help you along.
>
> Thanks
> Joe
>
> On Tue, Jun 6, 2017 at 3:12 AM, Venkat Williams
> <venkat.williams@gmail.com> wrote:
> > Hi
> >
> >
> >
> > I want to contribute this processor implementation code to NIFI project.
> >
> >
> >
> > Requirements:
> >
> >
> >
> > 1)     Convert CSV files to a standard/canonical JSON format
> >
> > a.       One JSON object/document per row in the input CSV
> >
> > b.      Format should encode the data as JSON fields and values
> >
> > c.       JSON Field names should be the original column header with any
> > invalid characters handled properly.
> >
> > d.      Values should be kept unaltered
> >
> > 2)     Optionally, be able to specify an expected header used to
> > validate/reject input CSVs
> >
> > 3)     Support both tab and comma delimited files
> >
> > a.     Auto-detect based on header row is easy
> >
> > b.    Allow operator to specify the delimiter as a way to override the
> > auto-detect logic
> >
> > 4)     Handle arbitrarily large files...
> >
> > a.       should handle CSV files of any length ( achieve this using
> > batching)
> >
> > 5)     Handle errors gracefully
> >
> > a.       File failures
> >
> > b.      Row failures
> >
> > 6)     Support for RFC-4180 formatted CSV files and be sure to handle
> edge
> > cases like embedded newlines in a field value and escaped double quotes
> >
> >
> >
> > Example:
> >
> > Input CSV:
> >
> > user,source_ip,source_country,destination_ip,url,timestamp
> >
> > Venkat,192.168.0.1,IN,23.246.97.82,http://www.google.com,
> 2017-02-22T14:46:24-05:00
> >
> >
> >
> > Desired output JSON:
> >
> > {"user":"Venkat","source_ip":"192.168.0.1","source_country":
> "IN","destination_ip":"23.246.97.82","url":"http://www.google.com
> ","timestamp":"2017-02-22T14:46:24-05:00"}
> >
> >
> >
> > Implementation:
> >
> > 1)      Reviewed all the existing csv libraries which can be used to
> > transform csv record to json document by supporting  RFC-4180 standard to
> > handle embedded new lines in field value and escaped quotes. Found
> OpenCSV,
> > FastCSV, UnivocityCSV Libraries can do this job most effectively.
> >
> > 2)      Selected Univocity CSV Library as I can do most of validations
> which
> > are part of my requirements only using this library. When I did the
> > performance testing using 5 GB and 10GB arbitrarily large files this gave
> > better results compared any others.
> >
> > 3)      Processed CSV Records are being emitted immediately rather than
> > waiting complete file processing. Used some configurable number in
> processor
> > to wait until that many records to emit. With this approach I could
> process
> > 5GB CSV data records using 1GB NIFI RAM which is most effective /
> attractive
> > feature in this whole implementation to handle large files. ( This is
> common
> > limitation in most of processors like SplitText, SplitXML, etc wait until
> > whole file processing and stores the results FlowFile ArrayList within
> the
> > processor this cause heap size/outofmemory issues)
> >
> > 4) Handled File errors and record errors gracefully using user defined
> > configurations and processor routes.
> >
> > Can anyone suggest how to proceed further whether I have to open new
> issue
> > or if I have to use any existing issue. ( I don't find any which matches
> to
> > this requirement)
>

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