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From: Bhupesh Chawda <bhupesh@datatorrent.com>
Date: Wed, 4 Jan 2017 12:36:16 +0530
Message-ID: <CAHvM9d1NcuT-PUPawgb4UPzWZWRt7P8vhrn225inEa=2HwhhZw@mail.gmail.com>
Subject: Re: [DISCUSS] Custom Control Tuples Design
To: dev <dev@apex.apache.org>
Content-Type: multipart/alternative; boundary=001a1137a222f9791905453f6c85
archived-at: Wed, 04 Jan 2017 07:06:50 -0000

--001a1137a222f9791905453f6c85
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Hi Pramod,

I was thinking of a method setPropagateControlTuples(boolean propagate) on
the output port of the operator.
The operator could disable this in the code at any point of time.
Note however that this is to block the propagation of control tuples from
upstream. Any control tuples emitted explicitly by the operator would still
be emitted and sent to the downstream operators.

Please see
https://github.com/apache/apex-core/pull/440/files#diff-8aa0ca1a3e645fa60e9b376c118c00a3R68
in the PR.

~ Bhupesh

On Wed, Jan 4, 2017 at 6:53 AM, Pramod Immaneni <pramod@datatorrent.com>
wrote:

> 2 sounds good. Have you thought about what the method would look like.
>
> On Sat, Dec 31, 2016 at 8:29 PM, Bhupesh Chawda <bhupesh@datatorrent.com>
> wrote:
>
> > Yes, that makes sense.
> > We have following options:
> > 1. Make the annotation false by default and force the user to forward the
> > control tuples explicitly.
> > 2. Annotation is true by default and static way of blocking stays as it
> is.
> > We provide another way for blocking programmatically, perhaps by means of
> > another method call on the port.
> >
> > ~ Bhupesh
> >
> > On Dec 30, 2016 00:09, "Pramod Immaneni" <pramod@datatorrent.com> wrote:
> >
> > > Bhupesh,
> > >
> > > Annotation seems like a static way to stop propagation. Give these are
> > > programmatically generated I would think the operators should be able
> to
> > > stop (consume without propagating) programmatically as well.
> > >
> > > Thanks
> > >
> > > On Thu, Dec 29, 2016 at 8:48 AM, Bhupesh Chawda <
> bhupesh@datatorrent.com
> > >
> > > wrote:
> > >
> > > > Thanks Vlad, I am trying out the approach you mentioned regarding
> > having
> > > > another interface which allows sinks to put a control tuple.
> > > >
> > > > Regarding the delivery of control tuples, here is what I am planning
> to
> > > do:
> > > > All the control tuples which are emitted in a particular window are
> > > > delivered after all the data tuples have been delivered to the
> > respective
> > > > ports, but before the endWindow() call. The operator can then process
> > the
> > > > control tuples in that window and can do any finalization in the end
> > > window
> > > > call. There will be no delivery of control tuples after endWindow()
> and
> > > > before the next beginWindow() call.
> > > >
> > > > For handling the propagation of control tuples further in the dag, we
> > are
> > > > planning to have an annotation on the Output Port of the operator
> which
> > > > would be true by default.
> > > > @OutputPortFieldAnnotation(propogateControlTuples = false).
> > > >
> > > > ~ Bhupesh
> > > >
> > > >
> > > > On Thu, Dec 29, 2016 at 6:24 AM, Vlad Rozov <v.rozov@datatorrent.com
> >
> > > > wrote:
> > > >
> > > > > Custom control tuples are control tuples emitted by an operator
> > itself
> > > > and
> > > > > not by the platform. Prior to the introduction of the custom
> control
> > > > > tuples, only Apex engine itself puts control tuples into various
> > sinks,
> > > > so
> > > > > the engine created necessary Tuple objects with the corresponding
> > type
> > > > > prior to calling Sink.put().
> > > > >
> > > > > Not all sinks need to be changed. Only control tuple aware sinks
> > should
> > > > > provide such functionality. In the case there is a lot of code
> > > > duplication,
> > > > > please create an abstract class, that other control aware sinks
> will
> > > > extend
> > > > > from.
> > > > >
> > > > > Thank you,
> > > > >
> > > > > Vlad
> > > > >
> > > > >
> > > > > On 12/23/16 06:24, Bhupesh Chawda wrote:
> > > > >
> > > > >> Hi Vlad,
> > > > >>
> > > > >> Thanks for the pointer on delegating the wrapping of the user
> tuple
> > to
> > > > the
> > > > >> control port. I was trying this out today.
> > > > >> The problem I see us if we introduce a putControlTuple() method in
> > > Sink,
> > > > >> then a lot of the existing sinks would change. Also the changes
> > seemed
> > > > >> redundant as, the existing control tuples already use the put()
> > method
> > > > of
> > > > >> sinks. So why do something special for custom control tuples?
> > > > >>
> > > > >> The only aspect in which the custom control tuples are different
> is
> > > that
> > > > >> these will be generated by the user and will actually be delivered
> > to
> > > > the
> > > > >> ports in a different order. Perhaps we should be able to use the
> > > > existing
> > > > >> flow. The only problems as outlined before seem to be
> identification
> > > of
> > > > >> the
> > > > >> user tuple as a control tuple.
> > > > >>
> > > > >> ~ Bhupesh
> > > > >>
> > > > >>
> > > > >> On Thu, Dec 22, 2016 at 10:44 PM, Vlad Rozov <
> > v.rozov@datatorrent.com
> > > >
> > > > >> wrote:
> > > > >>
> > > > >> Why is it necessary to wrap in the OutputPort? Can't it be
> delegated
> > > to
> > > > a
> > > > >>> Sink by introducing new putControlTuple method?
> > > > >>>
> > > > >>> Thank you,
> > > > >>>
> > > > >>> Vlad
> > > > >>>
> > > > >>>
> > > > >>> On 12/21/16 22:10, Bhupesh Chawda wrote:
> > > > >>>
> > > > >>> Hi Vlad,
> > > > >>>>
> > > > >>>> The problem in using the Tuple class as the wrapper is that the
> > > Ports
> > > > >>>> belong to the API and we want to wrap the payload object of the
> > > > control
> > > > >>>> tuple into the Tuple class which is not part of the API.
> > > > >>>>
> > > > >>>> The output port will just get the payload of the user control
> > tuple.
> > > > For
> > > > >>>> example, if the user emits a Long, as a control tuple, the
> payload
> > > > >>>> object
> > > > >>>> will just be a Long object.
> > > > >>>>
> > > > >>>> It is necessary to bundle this Long into some recognizable
> object
> > so
> > > > >>>> that
> > > > >>>> the BufferServerPublisher knows that this is a Control tuple and
> > > not a
> > > > >>>> regular tuple and serialize it accordingly. It is therefore
> > > necessary
> > > > >>>> that
> > > > >>>> the tuple be part of some known hierarchy so that can be
> > > distinguished
> > > > >>>> from
> > > > >>>> other payload tuples. Let us call this class
> > ControlTupleInterface.
> > > > Note
> > > > >>>> that this needs to be done before the tuple is inserted into the
> > > sink
> > > > >>>> which
> > > > >>>> is done in the port objects. Once the tuple is inserted into the
> > > sink,
> > > > >>>> it
> > > > >>>> would seem just like any other payload tuple and cannot be
> > > > >>>> distinguished.
> > > > >>>>
> > > > >>>> For this reason, I had something like the following in API:
> > > > >>>>
> > > > >>>> package com.datatorrent.api;
> > > > >>>> public class ControlTupleInterface
> > > > >>>> {
> > > > >>>>     Object payload; // User control tuple payload. A Long() for
> > > > example.
> > > > >>>>     UUID id;  // Unique Id to de-duplicate in downstream
> operators
> > > > >>>> }
> > > > >>>>
> > > > >>>> Regarding your suggestion on using the Tuple class as the
> wrapper
> > > for
> > > > >>>> the
> > > > >>>> control tuple payload, let me mention the current scenario flow
> to
> > > > make
> > > > >>>> the
> > > > >>>> discussion easier:
> > > > >>>>
> > > > >>>> We have a Tuple class in buffer server which is responsible for
> > > > >>>> serializing
> > > > >>>> the user control tuple bundling together a message type:
> > > > >>>> CUSTOM_CONTROL_TUPLE_VALUE.
> > > > >>>>
> > > > >>>>
> > > > >>>> *com.datatorrent.bufferserver.packet.Tuple|--
> > > > >>>> com.datatorrent.bufferserver.packet.CustomControlTuple*
> > > > >>>> We have another Tuple class in Stram which helps the
> > > > >>>> BufferServerSubscriber
> > > > >>>> to de-serialize the serialized tuples. We should have
> > > > CustomControlTuple
> > > > >>>> in
> > > > >>>> stram as follows:
> > > > >>>>
> > > > >>>>
> > > > >>>> *com.datatorrent.stram.tuple.Tuple|--
> > > > >>>> com.datatorrent.stram.tuple.CustomControlTuple*This will have a
> > > field
> > > > >>>> for
> > > > >>>>
> > > > >>>> user control payload.
> > > > >>>>
> > > > >>>> I think we should not expose the Tuple class in stram to the
> API.
> > > That
> > > > >>>> was
> > > > >>>> the main reason I introduced another class/interface
> > > > >>>> ControlTupleInterface
> > > > >>>> as described above.
> > > > >>>>
> > > > >>>> Regarding, adding methods to DefaultInputPort and
> > > DefaultOutputPort, I
> > > > >>>> think error detection would not be early enough if the control
> > tuple
> > > > is
> > > > >>>> sent very late in the processing :-)
> > > > >>>> Extending the ports to ControlTupleAware* should help in this
> > case.
> > > > >>>> However, we still need to see if there are any downsides on
> doing
> > > > this.
> > > > >>>>
> > > > >>>> Thanks.
> > > > >>>>
> > > > >>>> ~ Bhupesh
> > > > >>>>
> > > > >>>>
> > > > >>>>
> > > > >>>>
> > > > >>>> On Thu, Dec 22, 2016 at 7:26 AM, Vlad Rozov <
> > > v.rozov@datatorrent.com>
> > > > >>>> wrote:
> > > > >>>>
> > > > >>>> Hi Bhupesh,
> > > > >>>>
> > > > >>>>> it should not be a CustomWrapper.  The wrapper object should be
> > > > >>>>> CustomControlTuple that extends Tuple. There is already code
> that
> > > > >>>>> checks
> > > > >>>>> for Tuple instance. The "unWrap" name is misleading, IMO. It
> > should
> > > > be
> > > > >>>>> something like customControlTuple.getPayload() or
> > > > >>>>> customControlTuple.getAttachment(). In the emitControl(),
> create
> > > new
> > > > >>>>> CustomControlTuple using provided payload as one of arguments.
> It
> > > may
> > > > >>>>> still
> > > > >>>>> be good to use common parent other than Object for control
> tuple
> > > > >>>>> payload
> > > > >>>>> class hierarchy.
> > > > >>>>>
> > > > >>>>> I don't understand how adding more methods to the Default
> > > > >>>>> implementation
> > > > >>>>> will help with early error detection unless application or
> > operator
> > > > >>>>> that
> > > > >>>>> relies on the custom control tuple functionality explicitly
> > checks
> > > > for
> > > > >>>>> the
> > > > >>>>> platform version at run-time or tries to emit a control tuple
> > just
> > > to
> > > > >>>>> check
> > > > >>>>> that such functionality is supported by the platform.
> > > > >>>>>
> > > > >>>>> Thank you,
> > > > >>>>>
> > > > >>>>> Vlad
> > > > >>>>>
> > > > >>>>> On 12/21/16 04:58, Bhupesh Chawda wrote:
> > > > >>>>>
> > > > >>>>> Hi Vlad.
> > > > >>>>>
> > > > >>>>>> Yes, the API should not change. We can take an Object instead,
> > and
> > > > >>>>>> later
> > > > >>>>>> wrap it into the required class.
> > > > >>>>>>
> > > > >>>>>> Our InputPort.put and emitControl method would look something
> > like
> > > > the
> > > > >>>>>> following where we handle the wrapping and unwrapping
> > internally.
> > > > >>>>>>
> > > > >>>>>> public void put(T tuple)
> > > > >>>>>> {
> > > > >>>>>>      if (tuple instanceof CustomWrapper) {
> > > > >>>>>>        processControl(tuple.unWrap());
> > > > >>>>>>      }  else {
> > > > >>>>>>        process(tuple)
> > > > >>>>>>      }
> > > > >>>>>> }
> > > > >>>>>>
> > > > >>>>>> emitControl(Object tuple)
> > > > >>>>>> {
> > > > >>>>>>      sink.put(CustomWrapper.wrap(tuple));
> > > > >>>>>> }
> > > > >>>>>>
> > > > >>>>>> Regarding the compatibility issue, I think we have two ways of
> > > doing
> > > > >>>>>> it:
> > > > >>>>>>
> > > > >>>>>>       1. Extend DefaultInputPort and DefaultOutputPort and
> > create
> > > > >>>>>>       ControlAwareInput and ControlAwareOutput out of it. This
> > > might
> > > > >>>>>> require us
> > > > >>>>>>       to additionally handle specific cases when
> non-compatible
> > > > ports
> > > > >>>>>>       (ControlAwareOutput and DefaultInput, for example) are
> > > > >>>>>> connected to
> > > > >>>>>> each
> > > > >>>>>>       other in user apps.
> > > > >>>>>>       2. Add the additional methods in the existing Default
> > > > >>>>>> implementations.
> > > > >>>>>>
> > > > >>>>>>
> > > > >>>>>> IMO, both of these would help in early error detection.
> > > > >>>>>>
> > > > >>>>>> ~ Bhupesh
> > > > >>>>>>
> > > > >>>>>>
> > > > >>>>>>
> > > > >>>>>>
> > > > >>>>>> On Wed, Dec 21, 2016 at 1:36 AM, Vlad Rozov <
> > > > v.rozov@datatorrent.com>
> > > > >>>>>> wrote:
> > > > >>>>>>
> > > > >>>>>> A wrapper class is required for the control tuples delivery,
> but
> > > > >>>>>>
> > > > >>>>>> Port/Operator API should use Control Tuple payload object
> only.
> > > > >>>>>>> Implementation of the wrapper class may change from version
> to
> > > > >>>>>>> version,
> > > > >>>>>>> but
> > > > >>>>>>> API should not be affected by the change.
> > > > >>>>>>>
> > > > >>>>>>> I guess, assumption is that default input and output port
> will
> > be
> > > > >>>>>>> extended
> > > > >>>>>>> to provide support for the control tuples. This may cause
> some
> > > > >>>>>>> backward
> > > > >>>>>>> compatibility issues. Consider scenario when a newer version
> of
> > > > >>>>>>> Malhar
> > > > >>>>>>> that
> > > > >>>>>>> relies on EOF control tuple is deployed into older version of
> > > core
> > > > >>>>>>> that
> > > > >>>>>>> does not support control tuples. In such scenario, error will
> > be
> > > > >>>>>>> raised
> > > > >>>>>>> only when an operator tries to emit EOF control tuple at the
> > end
> > > > of a
> > > > >>>>>>> job.
> > > > >>>>>>> Introducing control tuple aware ports solve the early error
> > > > >>>>>>> detection.
> > > > >>>>>>> It
> > > > >>>>>>> will require some operators to be modified to use control
> tuple
> > > > aware
> > > > >>>>>>> ports, but such change may help to distinguish control tuple
> > > aware
> > > > >>>>>>> operators from their old versions.
> > > > >>>>>>>
> > > > >>>>>>> Vlad
> > > > >>>>>>>
> > > > >>>>>>> On 12/20/16 04:09, Bhupesh Chawda wrote:
> > > > >>>>>>>
> > > > >>>>>>> I investigated this and seems like it is better to have a
> > wrapper
> > > > >>>>>>> class
> > > > >>>>>>>
> > > > >>>>>>> for
> > > > >>>>>>>> the user object.
> > > > >>>>>>>> This would serve 2 purposes:
> > > > >>>>>>>>
> > > > >>>>>>>>        1. Allow us to distinguish a custom control tuple
> from
> > > > other
> > > > >>>>>>>> payload
> > > > >>>>>>>>        tuples.
> > > > >>>>>>>>        2. For the same control tuple received from different
> > > > >>>>>>>> upstream
> > > > >>>>>>>>
> > > > >>>>>>>>        partitions, we would have some mechanism to
> distinguish
> > > > >>>>>>>> between
> > > > >>>>>>>> the
> > > > >>>>>>>> two in
> > > > >>>>>>>>        order to identify duplicates.
> > > > >>>>>>>>
> > > > >>>>>>>> Additionally, the wrapper class needs to be part of the API
> as
> > > > >>>>>>>> DefaultOutputPort needs to know about it, before putting it
> > into
> > > > the
> > > > >>>>>>>> sink.
> > > > >>>>>>>> We can make sure that the user is not able to extend or
> modify
> > > > this
> > > > >>>>>>>> class
> > > > >>>>>>>> in any manner.
> > > > >>>>>>>>
> > > > >>>>>>>> ~ Bhupesh
> > > > >>>>>>>>
> > > > >>>>>>>> On Mon, Dec 19, 2016 at 12:18 PM, David Yan <
> > davidyan@gmail.com
> > > >
> > > > >>>>>>>> wrote:
> > > > >>>>>>>>
> > > > >>>>>>>> This C type parameter is going to fix the control tuple type
> > at
> > > > >>>>>>>> compile
> > > > >>>>>>>>
> > > > >>>>>>>> time and this is actually not what we want. Note that the
> > > operator
> > > > >>>>>>>> may
> > > > >>>>>>>>
> > > > >>>>>>>>> receive or emit multiple different control tuple types.
> > > > >>>>>>>>>
> > > > >>>>>>>>> David
> > > > >>>>>>>>>
> > > > >>>>>>>>> On Dec 17, 2016 3:33 AM, "Tushar Gosavi" <
> > > tushar@datatorrent.com
> > > > >
> > > > >>>>>>>>> wrote:
> > > > >>>>>>>>>
> > > > >>>>>>>>> We do not need to create an interface for data emitted
> > through
> > > > >>>>>>>>> emitControl or processed through processControl. Internally
> > we
> > > > >>>>>>>>> could
> > > > >>>>>>>>> wrap the user object in ControlTuple. you can add type
> > > parameter
> > > > >>>>>>>>> for
> > > > >>>>>>>>> control tuple object on ports.
> > > > >>>>>>>>>
> > > > >>>>>>>>> DefaultInputPort<D,C>
> > > > >>>>>>>>> D is the data type and C is the control tuple type for
> better
> > > > error
> > > > >>>>>>>>> catching at compile phase.
> > > > >>>>>>>>>
> > > > >>>>>>>>>
> > > > >>>>>>>>> - Tushar.
> > > > >>>>>>>>>
> > > > >>>>>>>>>
> > > > >>>>>>>>> On Sat, Dec 17, 2016 at 8:35 AM, Bhupesh Chawda <
> > > > >>>>>>>>> bhupesh@datatorrent.com
> > > > >>>>>>>>> wrote:
> > > > >>>>>>>>>
> > > > >>>>>>>>> Agreed Vlad and David.
> > > > >>>>>>>>>
> > > > >>>>>>>>> I am just suggesting there should be a wrapper for the user
> > > > object.
> > > > >>>>>>>>>> It
> > > > >>>>>>>>>>
> > > > >>>>>>>>>> can
> > > > >>>>>>>>>>
> > > > >>>>>>>>>> be a marker interface and we can call it something else
> like
> > > > >>>>>>>>>
> > > > >>>>>>>>> "CustomControl".
> > > > >>>>>>>>>>
> > > > >>>>>>>>>> The user object will be wrapped in another class
> > > "ControlTuple"
> > > > >>>>>>>>>> which
> > > > >>>>>>>>>> traverses the BufferServer and will perhaps be extended
> from
> > > the
> > > > >>>>>>>>>> packet/Tuple class. This class will not be exposed to the
> > > user.
> > > > >>>>>>>>>>
> > > > >>>>>>>>>> ~ Bhupesh
> > > > >>>>>>>>>>
> > > > >>>>>>>>>>
> > > > >>>>>>>>>> On Sat, Dec 17, 2016 at 4:11 AM, Vlad Rozov <
> > > > >>>>>>>>>> v.rozov@datatorrent.com>
> > > > >>>>>>>>>>
> > > > >>>>>>>>>> wrote:
> > > > >>>>>>>>>>
> > > > >>>>>>>>>> I agree with David. Payload of the control tuple is in the
> > > > >>>>>>>>> userObject
> > > > >>>>>>>>>
> > > > >>>>>>>>> and
> > > > >>>>>>>>>> operators/ports don't need to be exposed to the
> > implementation
> > > > of
> > > > >>>>>>>>>> the
> > > > >>>>>>>>>>
> > > > >>>>>>>>>> ControlTuple class. With the proposed interface operators
> > > > >>>>>>>>>> developers
> > > > >>>>>>>>>>
> > > > >>>>>>>>>>> are
> > > > >>>>>>>>>>> free to extend ControlTuple further and I don't think
> that
> > > such
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>>> capability
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>>> needs to be provided. The wrapping in the ControlTuple
> > class
> > > is
> > > > >>>>>>>>>> necessary
> > > > >>>>>>>>>> and most likely ControlTuple needs to be extended from the
> > > > buffer
> > > > >>>>>>>>>> server
> > > > >>>>>>>>>>
> > > > >>>>>>>>>> Tuple. It may be good to have a common parent other than
> > > Object
> > > > >>>>>>>>>> for
> > > > >>>>>>>>>>
> > > > >>>>>>>>>>> all
> > > > >>>>>>>>>>> user payloads, but it may be a marker interface as well.
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>>> Thank you,
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>>> Vlad
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>>> On 12/16/16 09:59, Bhupesh Chawda wrote:
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>>> Hi David,
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>>> Actually, I was thinking of another API class called
> > > > >>>>>>>>>>> ControlTuple,
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>>>> different from the actual tuple class in buffer server
> or
> > > > stram.
> > > > >>>>>>>>>>>> This could serve as a way for the Buffer server
> publisher
> > to
> > > > >>>>>>>>>>>> understand
> > > > >>>>>>>>>>>> that it is a control tuple and needs to be wrapped
> > > > differently.
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>>> ~ Bhupesh
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>>> On Dec 16, 2016 22:28, "David Yan" <davidyan@gmail.com>
> > > > wrote:
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>>>       // DefaultInputPort
> > > > >>>>>>>>>>>>        public void processControl(ControlTuple tuple)
> > > > >>>>>>>>>>>>        {
> > > > >>>>>>>>>>>>          // Default Implementation to avoid need to
> > > implement
> > > > >>>>>>>>>>>> it in
> > > > >>>>>>>>>>>> all
> > > > >>>>>>>>>>>> implementations
> > > > >>>>>>>>>>>>        }
> > > > >>>>>>>>>>>> {code}
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>>> {code}
> > > > >>>>>>>>>>>>       // DefaultOutputPort
> > > > >>>>>>>>>>>>        public void emitControl(ControlTuple tuple)
> > > > >>>>>>>>>>>>        {
> > > > >>>>>>>>>>>>        }
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>>> I think we don't need to expose the ControlTuple class
> to
> > > the
> > > > >>>>>>>>>>>> operator
> > > > >>>>>>>>>>>> developers because the window ID is just the current
> > window
> > > ID
> > > > >>>>>>>>>>>> when
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>>> these
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>>> methods are called. How about making them just Object?
> We
> > > also
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>> need to
> > > > >>>>>>>>>>
> > > > >>>>>>>>>> provide the way for the user to specify custom serializer
> > for
> > > > the
> > > > >>>>>>>>>>
> > > > >>>>>>>>>>> control
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>>> tuple.
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>> David
> > > > >>>>>>>>>>
> > > > >>>>>>>>>>> On Thu, Dec 15, 2016 at 12:43 AM, Bhupesh Chawda <
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>>> bhupesh@datatorrent.com
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>>> wrote:
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>> Hi All,
> > > > >>>>>>>>>>
> > > > >>>>>>>>>>> Here are the initial interfaces:
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>>> {code}
> > > > >>>>>>>>>>>>>       // DefaultInputPort
> > > > >>>>>>>>>>>>>        public void processControl(ControlTuple tuple)
> > > > >>>>>>>>>>>>>        {
> > > > >>>>>>>>>>>>>          // Default Implementation to avoid need to
> > > implement
> > > > >>>>>>>>>>>>> it
> > > > >>>>>>>>>>>>> in
> > > > >>>>>>>>>>>>> all
> > > > >>>>>>>>>>>>> implementations
> > > > >>>>>>>>>>>>>        }
> > > > >>>>>>>>>>>>> {code}
> > > > >>>>>>>>>>>>>
> > > > >>>>>>>>>>>>> {code}
> > > > >>>>>>>>>>>>>       // DefaultOutputPort
> > > > >>>>>>>>>>>>>        public void emitControl(ControlTuple tuple)
> > > > >>>>>>>>>>>>>        {
> > > > >>>>>>>>>>>>>        }
> > > > >>>>>>>>>>>>> {code}
> > > > >>>>>>>>>>>>>
> > > > >>>>>>>>>>>>> We have an option to add these methods to the
> interfaces
> > -
> > > > >>>>>>>>>>>>> InputPort
> > > > >>>>>>>>>>>>>
> > > > >>>>>>>>>>>>> and
> > > > >>>>>>>>>>>>>
> > > > >>>>>>>>>>>>> OutputPort; But these would not be backward compatible
> > and
> > > > also
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>> not
> > > > >>>>>>>>>>> consistent with the current implementation of basic data
> > > tuple
> > > > >>>>>>>>>>> flow
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>>> (as
> > > > >>>>>>>>>>>> with process() and emit()).
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>> We also need to expose an interface / class for users to
> > wrap
> > > > >>>>>>>>>>> their
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>>> object
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>>>> and emit downstream. This should be part of API.
> > > > >>>>>>>>>>>>>
> > > > >>>>>>>>>>>>> {code}
> > > > >>>>>>>>>>>>> public class ControlTuple extends Tuple
> > > > >>>>>>>>>>>>> {
> > > > >>>>>>>>>>>>>        Object userObject;
> > > > >>>>>>>>>>>>>
> > > > >>>>>>>>>>>>>        public ControlTuple(long windowId, Object
> > > userObject)
> > > > >>>>>>>>>>>>>        {
> > > > >>>>>>>>>>>>>          //
> > > > >>>>>>>>>>>>>        }
> > > > >>>>>>>>>>>>> }
> > > > >>>>>>>>>>>>> {code}
> > > > >>>>>>>>>>>>>
> > > > >>>>>>>>>>>>> The emitted tuples would traverse the same flow as with
> > > other
> > > > >>>>>>>>>>>>> control
> > > > >>>>>>>>>>>>> tuples. The plan is to intercept the control tuples in
> > > > >>>>>>>>>>>>> GenericNode
> > > > >>>>>>>>>>>>> and
> > > > >>>>>>>>>>>>> use
> > > > >>>>>>>>>>>>> the Reservior to emit the control tuples at the end of
> > the
> > > > >>>>>>>>>>>>> window.
> > > > >>>>>>>>>>>>>
> > > > >>>>>>>>>>>>> GenericNode seems to be the best place to buffer
> incoming
> > > > >>>>>>>>>>>>> custom
> > > > >>>>>>>>>>>>>
> > > > >>>>>>>>>>>>> control
> > > > >>>>>>>>>>>>>
> > > > >>>>>>>>>>>>> tuples without delivering them immediately to the
> > operator
> > > > >>>>>>>>>>>> port.
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>> Once
> > > > >>>>>>>>>>> the
> > > > >>>>>>>>>>> end of the window is reached, we plan to use the
> reservoir
> > > sink
> > > > >>>>>>>>>>> to
> > > > >>>>>>>>>>> push
> > > > >>>>>>>>>>> them to the port. This is different behavior than any
> other
> > > > >>>>>>>>>>> control
> > > > >>>>>>>>>>> tuple
> > > > >>>>>>>>>>> where we are changing the order of tuples in the stream.
> > The
> > > > >>>>>>>>>>> custom
> > > > >>>>>>>>>>> control
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>>> tuples will be buffered and not delivered to the ports
> > until
> > > > the
> > > > >>>>>>>>>>>> end
> > > > >>>>>>>>>>>> of
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>>> the
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>> window.
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>>> To accomplish this, we need to have a public method in
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>>>> SweepableReservoir
> > > > >>>>>>>>>>>>>
> > > > >>>>>>>>>>>>> which allows to put a tuple back in the sink of the
> > > > reservoir.
> > > > >>>>>>>>>>>>
> > > > >>>>>>>>>>> ~ Bhupesh
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>>>
> > > > >>>>>>>>>>>>>
> > > > >>>>>>>>>>>>>
> > > > >
> > > >
> > >
> >
>

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