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 <[email protected]> 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 <[email protected]> >> 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 <[email protected]> >>>> 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 <[email protected]> >>>>>> 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 <[email protected]> >>>>>>>> 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" <[email protected]> >>>>>>>>> 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 < >>>>>>>>> [email protected] >>>>>>>>> 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 < >>>>>>>>>> [email protected]> >>>>>>>>>> >>>>>>>>>> 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" <[email protected]> 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 < >>>>>>>>>>>> >>>>>>>>>>>> [email protected] >>>>>>>>>>>> >>>>>>>>>>>> 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 >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >
