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From: David Yan <davidyan@gmail.com>
Date: Tue, 28 Feb 2017 07:57:09 -0800
Message-ID: <CA+PLJDx2KfPQuaGmTHJLFxfBCas4=FWeJ7r1saW1jC0fE_xi9g@mail.gmail.com>
Subject: Re: [DISCUSS] Proposal for adapting Malhar operators for batch use cases
To: dev@apex.apache.org
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archived-at: Tue, 28 Feb 2017 15:57:44 -0000

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There is a discussion in the Flink mailing list about key-based watermarks.
I think it's relevant to our use case here.
https://lists.apache.org/thread.html/2b90d5b1d5e2654212cfbbcc6510ef424bbafc=
4fadb164bd5aff9216@%3Cdev.flink.apache.org%3E

David

On Tue, Feb 28, 2017 at 2:13 AM, Bhupesh Chawda <bhupesh@datatorrent.com>
wrote:

> Hi David,
>
> If using time window does not seem appropriate, we can have another class
> which is more suited for such sequential and distinct windows. Perhaps, a
> CustomWindow option can be introduced which takes in a window id. The
> purpose of this window option could be to translate the window id into
> appropriate timestamps.
>
> Another option would be to go with a custom timestampExtractor for such
> tuples which translates the each unique file name to a distinct timestamp
> while using time windows in the windowed operator.
>
> ~ Bhupesh
>
>
> _______________________________________________________
>
> Bhupesh Chawda
>
> E: bhupesh@datatorrent.com | Twitter: @bhupeshsc
>
> www.datatorrent.com  |  apex.apache.org
>
>
>
> On Tue, Feb 28, 2017 at 12:28 AM, David Yan <davidyan@gmail.com> wrote:
>
> > I now see your rationale on putting the filename in the window.
> > As far as I understand, the reasons why the filename is not part of the
> key
> > and the Global Window is not used are:
> >
> > 1) The files are processed in sequence, not in parallel
> > 2) The windowed operator should not keep the state associated with the
> file
> > when the processing of the file is done
> > 3) The trigger should be fired for the file when a file is done
> processing.
> >
> > However, if the file is just a sequence has nothing to do with a
> timestamp,
> > assigning a timestamp to a file is not an intuitive thing to do and wou=
ld
> > just create confusions to the users, especially when it's used as an
> > example for new users.
> >
> > How about having a separate class called SequenceWindow? And perhaps
> > TimeWindow can inherit from it?
> >
> > David
> >
> > On Mon, Feb 27, 2017 at 8:58 AM, Thomas Weise <thw@apache.org> wrote:
> >
> > > On Mon, Feb 27, 2017 at 8:50 AM, Bhupesh Chawda <
> bhupesh@datatorrent.com
> > >
> > > wrote:
> > >
> > > > I think my comments related to count based windows might be causing
> > > > confusion. Let's not discuss count based scenarios for now.
> > > >
> > > > Just want to make sure we are on the same page wrt. the "each file
> is a
> > > > batch" use case. As mentioned by Thomas, the each tuple from the sa=
me
> > > file
> > > > has the same timestamp (which is just a sequence number) and that
> helps
> > > > keep tuples from each file in a separate window.
> > > >
> > >
> > > Yes, in this case it is a sequence number, but it could be a time sta=
mp
> > > also, depending on the file naming convention. And if it was event ti=
me
> > > processing, the watermark would be derived from records within the
> file.
> > >
> > > Agreed, the source should have a mechanism to control the time stamp
> > > extraction along with everything else pertaining to the watermark
> > > generation.
> > >
> > >
> > > > We could also implement a "timestampExtractor" interface to identif=
y
> > the
> > > > timestamp (sequence number) for a file.
> > > >
> > > > ~ Bhupesh
> > > >
> > > >
> > > > _______________________________________________________
> > > >
> > > > Bhupesh Chawda
> > > >
> > > > E: bhupesh@datatorrent.com | Twitter: @bhupeshsc
> > > >
> > > > www.datatorrent.com  |  apex.apache.org
> > > >
> > > >
> > > >
> > > > On Mon, Feb 27, 2017 at 9:52 PM, Thomas Weise <thw@apache.org>
> wrote:
> > > >
> > > > > I don't think this is a use case for count based window.
> > > > >
> > > > > We have multiple files that are retrieved in a sequence and there
> is
> > no
> > > > > knowledge of the number of records per file. The requirement is t=
o
> > > > > aggregate each file separately and emit the aggregate when the fi=
le
> > is
> > > > read
> > > > > fully. There is no concept of "end of something" for an individua=
l
> > key
> > > > and
> > > > > global window isn't applicable.
> > > > >
> > > > > However, as already explained and implemented by Bhupesh, this ca=
n
> be
> > > > > solved using watermark and window (in this case the window
> timestamp
> > > > isn't
> > > > > a timestamp, but a file sequence, but that doesn't matter.
> > > > >
> > > > > Thomas
> > > > >
> > > > >
> > > > > On Mon, Feb 27, 2017 at 8:05 AM, David Yan <davidyan@gmail.com>
> > wrote:
> > > > >
> > > > > > I don't think this is the way to go. Global Window only means t=
he
> > > > > timestamp
> > > > > > does not matter (or that there is no timestamp). It does not
> > > > necessarily
> > > > > > mean it's a large batch. Unless there is some notion of event
> time
> > > for
> > > > > each
> > > > > > file, you don't want to embed the file into the window itself.
> > > > > >
> > > > > > If you want the result broken up by file name, and if the files
> are
> > > to
> > > > be
> > > > > > processed in parallel, I think making the file name be part of
> the
> > > key
> > > > is
> > > > > > the way to go. I think it's very confusing if we somehow make t=
he
> > > file
> > > > to
> > > > > > be part of the window.
> > > > > >
> > > > > > For count-based window, it's not implemented yet and you're
> welcome
> > > to
> > > > > add
> > > > > > that feature. In case of count-based windows, there would be no
> > > notion
> > > > of
> > > > > > time and you probably only trigger at the end of each window. I=
n
> > the
> > > > case
> > > > > > of count-based windows, the watermark only matters for batch
> since
> > > you
> > > > > need
> > > > > > a way to know when the batch has ended (if the count is 10, the
> > > number
> > > > of
> > > > > > tuples in the batch is let's say 105, you need a way to end the
> > last
> > > > > window
> > > > > > with 5 tuples).
> > > > > >
> > > > > > David
> > > > > >
> > > > > > On Mon, Feb 27, 2017 at 2:41 AM, Bhupesh Chawda <
> > > > bhupesh@datatorrent.com
> > > > > >
> > > > > > wrote:
> > > > > >
> > > > > > > Hi David,
> > > > > > >
> > > > > > > Thanks for your comments.
> > > > > > >
> > > > > > > The wordcount example that I created based on the windowed
> > operator
> > > > > does
> > > > > > > processing of word counts per file (each file as a separate
> > batch),
> > > > > i.e.
> > > > > > > process counts for each file and dump into separate files.
> > > > > > > As I understand Global window is for one large batch; i.e. al=
l
> > > > incoming
> > > > > > > data falls into the same batch. This could not be processed
> using
> > > > > > > GlobalWindow option as we need more than one windows. In this
> > > case, I
> > > > > > > configured the windowed operator to have time windows of 1ms
> each
> > > and
> > > > > > > passed data for each file with increasing timestamps: (file1,
> 1),
> > > > > (file2,
> > > > > > > 2) and so on. Is there a better way of handling this scenario=
?
> > > > > > >
> > > > > > > Regarding (2 - count based windows), I think there is a trigg=
er
> > > > option
> > > > > to
> > > > > > > process count based windows. In case I want to process every
> 1000
> > > > > tuples
> > > > > > as
> > > > > > > a batch, I could set the Trigger option to CountTrigger with
> the
> > > > > > > accumulation set to Discarding. Is this correct?
> > > > > > >
> > > > > > > I agree that (4. Final Watermark) can be done using Global
> > window.
> > > > > > >
> > > > > > > =E2=80=8B~ Bhupesh=E2=80=8B
> > > > > > >
> > > > > > > _______________________________________________________
> > > > > > >
> > > > > > > Bhupesh Chawda
> > > > > > >
> > > > > > > E: bhupesh@datatorrent.com | Twitter: @bhupeshsc
> > > > > > >
> > > > > > > www.datatorrent.com  |  apex.apache.org
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > On Mon, Feb 27, 2017 at 12:18 PM, David Yan <
> davidyan@gmail.com>
> > > > > wrote:
> > > > > > >
> > > > > > > > I'm worried that we are making the watermark concept too
> > > > complicated.
> > > > > > > >
> > > > > > > > Watermarks should simply just tell you what windows can be
> > > > considered
> > > > > > > > complete.
> > > > > > > >
> > > > > > > > Point 2 is basically a count-based window. Watermarks do no=
t
> > > play a
> > > > > > role
> > > > > > > > here because the window is always complete at the n-th tupl=
e.
> > > > > > > >
> > > > > > > > If I understand correctly, point 3 is for batch processing =
of
> > > > files.
> > > > > > > Unless
> > > > > > > > the files contain timed events, it sounds to be that this c=
an
> > be
> > > > > > achieved
> > > > > > > > with just a Global Window. For signaling EOF, a watermark
> with
> > a
> > > > > > > +infinity
> > > > > > > > timestamp can be used so that triggers will be fired upon
> > receipt
> > > > of
> > > > > > that
> > > > > > > > watermark.
> > > > > > > >
> > > > > > > > For point 4, just like what I mentioned above, can be
> achieved
> > > > with a
> > > > > > > > watermark with a +infinity timestamp.
> > > > > > > >
> > > > > > > > David
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > On Sat, Feb 18, 2017 at 8:04 AM, Bhupesh Chawda <
> > > > > > bhupesh@datatorrent.com
> > > > > > > >
> > > > > > > > wrote:
> > > > > > > >
> > > > > > > > > Hi Thomas,
> > > > > > > > >
> > > > > > > > > For an input operator which is supposed to generate
> > watermarks
> > > > for
> > > > > > > > > downstream operators, I can think about the following
> > > watermarks
> > > > > that
> > > > > > > the
> > > > > > > > > operator can emit:
> > > > > > > > > 1. Time based watermarks (the high watermark / low
> watermark)
> > > > > > > > > 2. Number of tuple based watermarks (Every n tuples)
> > > > > > > > > 3. File based watermarks (Start file, end file)
> > > > > > > > > 4. Final watermark
> > > > > > > > >
> > > > > > > > > File based watermarks seem to be applicable for batch (fi=
le
> > > > based)
> > > > > as
> > > > > > > > well,
> > > > > > > > > and hence I thought of looking at these first. Does this
> seem
> > > to
> > > > be
> > > > > > in
> > > > > > > > line
> > > > > > > > > with the thought process?
> > > > > > > > >
> > > > > > > > > ~ Bhupesh
> > > > > > > > >
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > _______________________________________________________
> > > > > > > > >
> > > > > > > > > Bhupesh Chawda
> > > > > > > > >
> > > > > > > > > Software Engineer
> > > > > > > > >
> > > > > > > > > E: bhupesh@datatorrent.com | Twitter: @bhupeshsc
> > > > > > > > >
> > > > > > > > > www.datatorrent.com  |  apex.apache.org
> > > > > > > > >
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > On Thu, Feb 16, 2017 at 10:37 AM, Thomas Weise <
> > thw@apache.org
> > > >
> > > > > > wrote:
> > > > > > > > >
> > > > > > > > > > I don't think this should be designed based on a
> simplistic
> > > > file
> > > > > > > > > > input-output scenario. It would be good to include a
> > stateful
> > > > > > > > > > transformation based on event time.
> > > > > > > > > >
> > > > > > > > > > More complex pipelines contain stateful transformations
> > that
> > > > > depend
> > > > > > > on
> > > > > > > > > > windowing and watermarks. I think we need a watermark
> > concept
> > > > > that
> > > > > > is
> > > > > > > > > based
> > > > > > > > > > on progress in event time (or other monotonic increasin=
g
> > > > > sequence)
> > > > > > > that
> > > > > > > > > > other operators can generically work with.
> > > > > > > > > >
> > > > > > > > > > Note that even file input in many cases can produce tim=
e
> > > based
> > > > > > > > > watermarks,
> > > > > > > > > > for example when you read part files that are bound by
> > event
> > > > > time.
> > > > > > > > > >
> > > > > > > > > > Thanks,
> > > > > > > > > > Thomas
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > On Wed, Feb 15, 2017 at 4:02 AM, Bhupesh Chawda <
> > > > > > > > bhupesh@datatorrent.com
> > > > > > > > > >
> > > > > > > > > > wrote:
> > > > > > > > > >
> > > > > > > > > > > For better understanding the use case for control
> tuples
> > in
> > > > > > batch,
> > > > > > > =E2=80=8BI
> > > > > > > > > am
> > > > > > > > > > > creating a prototype for a batch application using Fi=
le
> > > Input
> > > > > and
> > > > > > > > File
> > > > > > > > > > > Output operators.
> > > > > > > > > > >
> > > > > > > > > > > To enable basic batch processing for File IO
> operators, I
> > > am
> > > > > > > > proposing
> > > > > > > > > > the
> > > > > > > > > > > following changes to File input and output operators:
> > > > > > > > > > > 1. File Input operator emits a watermark each time it
> > opens
> > > > and
> > > > > > > > closes
> > > > > > > > > a
> > > > > > > > > > > file. These can be "start file" and "end file"
> watermarks
> > > > which
> > > > > > > > include
> > > > > > > > > > the
> > > > > > > > > > > corresponding file names. The "start file" tuple shou=
ld
> > be
> > > > sent
> > > > > > > > before
> > > > > > > > > > any
> > > > > > > > > > > of the data from that file flows.
> > > > > > > > > > > 2. File Input operator can be configured to end the
> > > > application
> > > > > > > > after a
> > > > > > > > > > > single or n scans of the directory (a batch). This is
> > where
> > > > the
> > > > > > > > > operator
> > > > > > > > > > > emits the final watermark (the end of application
> control
> > > > > tuple).
> > > > > > > > This
> > > > > > > > > > will
> > > > > > > > > > > also shutdown the application.
> > > > > > > > > > > 3. The File output operator handles these control
> tuples.
> > > > > "Start
> > > > > > > > file"
> > > > > > > > > > > initializes the file name for the incoming tuples. "E=
nd
> > > file"
> > > > > > > > watermark
> > > > > > > > > > > forces a finalize on that file.
> > > > > > > > > > >
> > > > > > > > > > > The user would be able to enable the operators to sen=
d
> > only
> > > > > those
> > > > > > > > > > > watermarks that are needed in the application. If non=
e
> of
> > > the
> > > > > > > options
> > > > > > > > > are
> > > > > > > > > > > configured, the operators behave as in a streaming
> > > > application.
> > > > > > > > > > >
> > > > > > > > > > > There are a few challenges in the implementation wher=
e
> > the
> > > > > input
> > > > > > > > > operator
> > > > > > > > > > > is partitioned. In this case, the correlation between
> the
> > > > > > start/end
> > > > > > > > > for a
> > > > > > > > > > > file and the data tuples for that file is lost. Hence
> we
> > > need
> > > > > to
> > > > > > > > > maintain
> > > > > > > > > > > the filename as part of each tuple in the pipeline.
> > > > > > > > > > >
> > > > > > > > > > > The "start file" and "end file" control tuples in thi=
s
> > > > example
> > > > > > are
> > > > > > > > > > > temporary names for watermarks. We can have generic
> > "start
> > > > > > batch" /
> > > > > > > > > "end
> > > > > > > > > > > batch" tuples which could be used for other use cases
> as
> > > > well.
> > > > > > The
> > > > > > > > > Final
> > > > > > > > > > > watermark is common and serves the same purpose in ea=
ch
> > > case.
> > > > > > > > > > >
> > > > > > > > > > > Please let me know your thoughts on this.
> > > > > > > > > > >
> > > > > > > > > > > ~ Bhupesh
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > On Wed, Jan 18, 2017 at 12:22 AM, Bhupesh Chawda <
> > > > > > > > > > bhupesh@datatorrent.com>
> > > > > > > > > > > wrote:
> > > > > > > > > > >
> > > > > > > > > > > > Yes, this can be part of operator configuration.
> Given
> > > > this,
> > > > > > for
> > > > > > > a
> > > > > > > > > user
> > > > > > > > > > > to
> > > > > > > > > > > > define a batch application, would mean configuring
> the
> > > > > > connectors
> > > > > > > > > > (mostly
> > > > > > > > > > > > the input operator) in the application for the
> desired
> > > > > > behavior.
> > > > > > > > > > > Similarly,
> > > > > > > > > > > > there can be other use cases that can be achieved
> other
> > > > than
> > > > > > > batch.
> > > > > > > > > > > >
> > > > > > > > > > > > We may also need to take care of the following:
> > > > > > > > > > > > 1. Make sure that the watermarks or control tuples
> are
> > > > > > consistent
> > > > > > > > > > across
> > > > > > > > > > > > sources. Meaning an HDFS sink should be able to
> > interpret
> > > > the
> > > > > > > > > watermark
> > > > > > > > > > > > tuple sent out by, say, a JDBC source.
> > > > > > > > > > > > 2. In addition to I/O connectors, we should also lo=
ok
> > at
> > > > the
> > > > > > need
> > > > > > > > for
> > > > > > > > > > > > processing operators to understand some of the
> control
> > > > > tuples /
> > > > > > > > > > > watermarks.
> > > > > > > > > > > > For example, we may want to reset the operator
> behavior
> > > on
> > > > > > > arrival
> > > > > > > > of
> > > > > > > > > > > some
> > > > > > > > > > > > watermark tuple.
> > > > > > > > > > > >
> > > > > > > > > > > > ~ Bhupesh
> > > > > > > > > > > >
> > > > > > > > > > > > On Tue, Jan 17, 2017 at 9:59 PM, Thomas Weise <
> > > > > thw@apache.org>
> > > > > > > > > wrote:
> > > > > > > > > > > >
> > > > > > > > > > > >> The HDFS source can operate in two modes, bounded =
or
> > > > > > unbounded.
> > > > > > > If
> > > > > > > > > you
> > > > > > > > > > > >> scan
> > > > > > > > > > > >> only once, then it should emit the final watermark
> > after
> > > > it
> > > > > is
> > > > > > > > done.
> > > > > > > > > > > >> Otherwise it would emit watermarks based on a poli=
cy
> > > > (files
> > > > > > > names
> > > > > > > > > > etc.).
> > > > > > > > > > > >> The mechanism to generate the marks may depend on
> the
> > > type
> > > > > of
> > > > > > > > source
> > > > > > > > > > and
> > > > > > > > > > > >> the user needs to be able to influence/configure i=
t.
> > > > > > > > > > > >>
> > > > > > > > > > > >> Thomas
> > > > > > > > > > > >>
> > > > > > > > > > > >>
> > > > > > > > > > > >> On Tue, Jan 17, 2017 at 5:03 AM, Bhupesh Chawda <
> > > > > > > > > > > bhupesh@datatorrent.com>
> > > > > > > > > > > >> wrote:
> > > > > > > > > > > >>
> > > > > > > > > > > >> > Hi Thomas,
> > > > > > > > > > > >> >
> > > > > > > > > > > >> > I am not sure that I completely understand your
> > > > > suggestion.
> > > > > > > Are
> > > > > > > > > you
> > > > > > > > > > > >> > suggesting to broaden the scope of the proposal =
to
> > > treat
> > > > > all
> > > > > > > > > sources
> > > > > > > > > > > as
> > > > > > > > > > > >> > bounded as well as unbounded?
> > > > > > > > > > > >> >
> > > > > > > > > > > >> > In case of Apex, we treat all sources as unbound=
ed
> > > > > sources.
> > > > > > > Even
> > > > > > > > > > > bounded
> > > > > > > > > > > >> > sources like HDFS file source is treated as
> > unbounded
> > > by
> > > > > > means
> > > > > > > > of
> > > > > > > > > > > >> scanning
> > > > > > > > > > > >> > the input directory repeatedly.
> > > > > > > > > > > >> >
> > > > > > > > > > > >> > Let's consider HDFS file source for example:
> > > > > > > > > > > >> > In this case, if we treat it as a bounded source=
,
> we
> > > can
> > > > > > > define
> > > > > > > > > > hooks
> > > > > > > > > > > >> which
> > > > > > > > > > > >> > allows us to detect the end of the file and send
> the
> > > > > "final
> > > > > > > > > > > watermark".
> > > > > > > > > > > >> We
> > > > > > > > > > > >> > could also consider HDFS file source as a
> streaming
> > > > source
> > > > > > and
> > > > > > > > > > define
> > > > > > > > > > > >> hooks
> > > > > > > > > > > >> > which send watermarks based on different kinds o=
f
> > > > windows.
> > > > > > > > > > > >> >
> > > > > > > > > > > >> > Please correct me if I misunderstand.
> > > > > > > > > > > >> >
> > > > > > > > > > > >> > ~ Bhupesh
> > > > > > > > > > > >> >
> > > > > > > > > > > >> >
> > > > > > > > > > > >> > On Mon, Jan 16, 2017 at 9:23 PM, Thomas Weise <
> > > > > > thw@apache.org
> > > > > > > >
> > > > > > > > > > wrote:
> > > > > > > > > > > >> >
> > > > > > > > > > > >> > > Bhupesh,
> > > > > > > > > > > >> > >
> > > > > > > > > > > >> > > Please see how that can be solved in a unified
> way
> > > > using
> > > > > > > > windows
> > > > > > > > > > and
> > > > > > > > > > > >> > > watermarks. It is bounded data vs. unbounded
> data.
> > > In
> > > > > Beam
> > > > > > > for
> > > > > > > > > > > >> example,
> > > > > > > > > > > >> > you
> > > > > > > > > > > >> > > can use the "global window" and the final
> > watermark
> > > to
> > > > > > > > > accomplish
> > > > > > > > > > > what
> > > > > > > > > > > >> > you
> > > > > > > > > > > >> > > are looking for. Batch is just a special case =
of
> > > > > streaming
> > > > > > > > where
> > > > > > > > > > the
> > > > > > > > > > > >> > source
> > > > > > > > > > > >> > > emits the final watermark.
> > > > > > > > > > > >> > >
> > > > > > > > > > > >> > > Thanks,
> > > > > > > > > > > >> > > Thomas
> > > > > > > > > > > >> > >
> > > > > > > > > > > >> > >
> > > > > > > > > > > >> > > On Mon, Jan 16, 2017 at 1:02 AM, Bhupesh Chawd=
a
> <
> > > > > > > > > > > >> bhupesh@datatorrent.com
> > > > > > > > > > > >> > >
> > > > > > > > > > > >> > > wrote:
> > > > > > > > > > > >> > >
> > > > > > > > > > > >> > > > Yes, if the user needs to develop a batch
> > > > application,
> > > > > > > then
> > > > > > > > > > batch
> > > > > > > > > > > >> aware
> > > > > > > > > > > >> > > > operators need to be used in the application=
.
> > > > > > > > > > > >> > > > The nature of the application is mostly
> > controlled
> > > > by
> > > > > > the
> > > > > > > > > input
> > > > > > > > > > > and
> > > > > > > > > > > >> the
> > > > > > > > > > > >> > > > output operators used in the application.
> > > > > > > > > > > >> > > >
> > > > > > > > > > > >> > > > For example, consider an application which
> needs
> > > to
> > > > > > filter
> > > > > > > > > > records
> > > > > > > > > > > >> in a
> > > > > > > > > > > >> > > > input file and store the filtered records in
> > > another
> > > > > > file.
> > > > > > > > The
> > > > > > > > > > > >> nature
> > > > > > > > > > > >> > of
> > > > > > > > > > > >> > > > this app is to end once the entire file is
> > > > processed.
> > > > > > > > > Following
> > > > > > > > > > > >> things
> > > > > > > > > > > >> > > are
> > > > > > > > > > > >> > > > expected of the application:
> > > > > > > > > > > >> > > >
> > > > > > > > > > > >> > > >    1. Once the input data is over, finalize
> the
> > > > output
> > > > > > > file
> > > > > > > > > from
> > > > > > > > > > > >> .tmp
> > > > > > > > > > > >> > > >    files. - Responsibility of output operato=
r
> > > > > > > > > > > >> > > >    2. End the application, once the data is
> read
> > > and
> > > > > > > > > processed -
> > > > > > > > > > > >> > > >    Responsibility of input operator
> > > > > > > > > > > >> > > >
> > > > > > > > > > > >> > > > These functions are essential to allow the
> user
> > to
> > > > do
> > > > > > > higher
> > > > > > > > > > level
> > > > > > > > > > > >> > > > operations like scheduling or running a
> workflow
> > > of
> > > > > > batch
> > > > > > > > > > > >> applications.
> > > > > > > > > > > >> > > >
> > > > > > > > > > > >> > > > I am not sure about intermediate (processing=
)
> > > > > operators,
> > > > > > > as
> > > > > > > > > > there
> > > > > > > > > > > >> is no
> > > > > > > > > > > >> > > > change in their functionality for batch use
> > cases.
> > > > > > > Perhaps,
> > > > > > > > > > > allowing
> > > > > > > > > > > >> > > > running multiple batches in a single
> application
> > > may
> > > > > > > require
> > > > > > > > > > > similar
> > > > > > > > > > > >> > > > changes in processing operators as well.
> > > > > > > > > > > >> > > >
> > > > > > > > > > > >> > > > ~ Bhupesh
> > > > > > > > > > > >> > > >
> > > > > > > > > > > >> > > > On Mon, Jan 16, 2017 at 2:19 PM, Priyanka
> > Gugale <
> > > > > > > > > > > priyag@apache.org
> > > > > > > > > > > >> >
> > > > > > > > > > > >> > > > wrote:
> > > > > > > > > > > >> > > >
> > > > > > > > > > > >> > > > > Will it make an impression on user that, i=
f
> he
> > > > has a
> > > > > > > batch
> > > > > > > > > > > >> usecase he
> > > > > > > > > > > >> > > has
> > > > > > > > > > > >> > > > > to use batch aware operators only? If so, =
is
> > > that
> > > > > what
> > > > > > > we
> > > > > > > > > > > expect?
> > > > > > > > > > > >> I
> > > > > > > > > > > >> > am
> > > > > > > > > > > >> > > > not
> > > > > > > > > > > >> > > > > aware of how do we implement batch scenari=
o
> so
> > > > this
> > > > > > > might
> > > > > > > > > be a
> > > > > > > > > > > >> basic
> > > > > > > > > > > >> > > > > question.
> > > > > > > > > > > >> > > > >
> > > > > > > > > > > >> > > > > -Priyanka
> > > > > > > > > > > >> > > > >
> > > > > > > > > > > >> > > > > On Mon, Jan 16, 2017 at 12:02 PM, Bhupesh
> > > Chawda <
> > > > > > > > > > > >> > > > bhupesh@datatorrent.com>
> > > > > > > > > > > >> > > > > wrote:
> > > > > > > > > > > >> > > > >
> > > > > > > > > > > >> > > > > > Hi All,
> > > > > > > > > > > >> > > > > >
> > > > > > > > > > > >> > > > > > While design / implementation for custom
> > > control
> > > > > > > tuples
> > > > > > > > is
> > > > > > > > > > > >> > ongoing, I
> > > > > > > > > > > >> > > > > > thought it would be a good idea to
> consider
> > > its
> > > > > > > > usefulness
> > > > > > > > > > in
> > > > > > > > > > > >> one
> > > > > > > > > > > >> > of
> > > > > > > > > > > >> > > > the
> > > > > > > > > > > >> > > > > > use cases -  batch applications.
> > > > > > > > > > > >> > > > > >
> > > > > > > > > > > >> > > > > > This is a proposal to adapt / extend
> > existing
> > > > > > > operators
> > > > > > > > in
> > > > > > > > > > the
> > > > > > > > > > > >> > Apache
> > > > > > > > > > > >> > > > > Apex
> > > > > > > > > > > >> > > > > > Malhar library so that it is easy to use
> > them
> > > in
> > > > > > batch
> > > > > > > > use
> > > > > > > > > > > >> cases.
> > > > > > > > > > > >> > > > > > Naturally, this would be applicable for
> > only a
> > > > > > subset
> > > > > > > of
> > > > > > > > > > > >> operators
> > > > > > > > > > > >> > > like
> > > > > > > > > > > >> > > > > > File, JDBC and NoSQL databases.
> > > > > > > > > > > >> > > > > > For example, for a file based store, (sa=
y
> > HDFS
> > > > > > store),
> > > > > > > > we
> > > > > > > > > > > could
> > > > > > > > > > > >> > have
> > > > > > > > > > > >> > > > > > FileBatchInput and FileBatchOutput
> operators
> > > > which
> > > > > > > allow
> > > > > > > > > > easy
> > > > > > > > > > > >> > > > integration
> > > > > > > > > > > >> > > > > > into a batch application. These operator=
s
> > > would
> > > > be
> > > > > > > > > extended
> > > > > > > > > > > from
> > > > > > > > > > > >> > > their
> > > > > > > > > > > >> > > > > > existing implementations and would be
> "Batch
> > > > > Aware",
> > > > > > > in
> > > > > > > > > that
> > > > > > > > > > > >> they
> > > > > > > > > > > >> > may
> > > > > > > > > > > >> > > > > > understand the meaning of some specific
> > > control
> > > > > > tuples
> > > > > > > > > that
> > > > > > > > > > > flow
> > > > > > > > > > > >> > > > through
> > > > > > > > > > > >> > > > > > the DAG. Start batch and end batch seem =
to
> > be
> > > > the
> > > > > > > > obvious
> > > > > > > > > > > >> > candidates
> > > > > > > > > > > >> > > > that
> > > > > > > > > > > >> > > > > > come to mind. On receipt of such control
> > > tuples,
> > > > > > they
> > > > > > > > may
> > > > > > > > > > try
> > > > > > > > > > > to
> > > > > > > > > > > >> > > modify
> > > > > > > > > > > >> > > > > the
> > > > > > > > > > > >> > > > > > behavior of the operator - to reinitiali=
ze
> > > some
> > > > > > > metrics
> > > > > > > > or
> > > > > > > > > > > >> finalize
> > > > > > > > > > > >> > > an
> > > > > > > > > > > >> > > > > > output file for example.
> > > > > > > > > > > >> > > > > >
> > > > > > > > > > > >> > > > > > We can discuss the potential control
> tuples
> > > and
> > > > > > > actions
> > > > > > > > in
> > > > > > > > > > > >> detail,
> > > > > > > > > > > >> > > but
> > > > > > > > > > > >> > > > > > first I would like to understand the vie=
ws
> > of
> > > > the
> > > > > > > > > community
> > > > > > > > > > > for
> > > > > > > > > > > >> > this
> > > > > > > > > > > >> > > > > > proposal.
> > > > > > > > > > > >> > > > > >
> > > > > > > > > > > >> > > > > > ~ Bhupesh
> > > > > > > > > > > >> > > > > >
> > > > > > > > > > > >> > > > >
> > > > > > > > > > > >> > > >
> > > > > > > > > > > >> > >
> > > > > > > > > > > >> >
> > > > > > > > > > > >>
> > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

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