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Posted to dev@flink.apache.org by Aljoscha Krettek <al...@apache.org> on 2015/05/05 13:37:37 UTC
[DISCUSS] Change Streaming Operators to be Push-Only
Hi Folks,
while working on introducing source-assigned timestamps into streaming
(https://issues.apache.org/jira/browse/FLINK-1967) I thought about how
the punctuations (low watermarks) can be pushed through the system.
The problem is, that operators can have two ways of getting input: 1.
They read directly from input iterators, and 2. They act as a
Collector and get elements via collect() from the previous operator in
a chain.
This makes it hard to push things through a chain that are not
elements, such as barriers and/or punctuations.
I propose to change all streaming operators to be push based, with a
slightly improved interface: In addition to collect(), which I would
call receiveElement() I would add receivePunctuation() and
receiveBarrier(). The first operator in the chain would also get data
from the outside invokable that reads from the input iterator and
calls receiveElement() for the first operator in a chain.
What do you think? I would of course be willing to implement this myself.
Cheers,
Aljoscha
Re: [DISCUSS] Change Streaming Operators to be Push-Only
Posted by Kostas Tzoumas <kt...@apache.org>.
oops, meant "iterators" :-)
On Tue, May 5, 2015 at 3:04 PM, Aljoscha Krettek <al...@apache.org>
wrote:
> What do you mean by "losing iterations"?
>
> For the pros and cons:
>
> Cons: I can't think of any, since most of the operators are chainable
> already and already behave like a collector.
>
> Pros:
> - Unified model for operators, chainable operators don't have to
> worry about input iterators and the collect interface.
> - Enables features that we want in the future, such as barriers and
> punctuations because they don't work with the
> simple Collector interface.
> - The while-loop is moved outside of the operators, now the Task (the
> thing that runs Operators) can control the flow of data better and
> deal with
> stuff like barriers and punctuations. If we want to keep the
> main-loop inside each operator, then they all have to manage input
> readers and inline events manually.
>
> On Tue, May 5, 2015 at 2:41 PM, Kostas Tzoumas <kt...@apache.org>
> wrote:
> > Can you give us a rough idea of the pros and cons? Do we lose some
> > functionality by getting rid of iterations?
> >
> > Kostas
> >
> > On Tue, May 5, 2015 at 1:37 PM, Aljoscha Krettek <al...@apache.org>
> > wrote:
> >
> >> Hi Folks,
> >> while working on introducing source-assigned timestamps into streaming
> >> (https://issues.apache.org/jira/browse/FLINK-1967) I thought about how
> >> the punctuations (low watermarks) can be pushed through the system.
> >> The problem is, that operators can have two ways of getting input: 1.
> >> They read directly from input iterators, and 2. They act as a
> >> Collector and get elements via collect() from the previous operator in
> >> a chain.
> >>
> >> This makes it hard to push things through a chain that are not
> >> elements, such as barriers and/or punctuations.
> >>
> >> I propose to change all streaming operators to be push based, with a
> >> slightly improved interface: In addition to collect(), which I would
> >> call receiveElement() I would add receivePunctuation() and
> >> receiveBarrier(). The first operator in the chain would also get data
> >> from the outside invokable that reads from the input iterator and
> >> calls receiveElement() for the first operator in a chain.
> >>
> >> What do you think? I would of course be willing to implement this
> myself.
> >>
> >> Cheers,
> >> Aljoscha
> >>
>
Re: [DISCUSS] Change Streaming Operators to be Push-Only
Posted by Aljoscha Krettek <al...@apache.org>.
There is already a Jira and a Pull Request:
https://github.com/apache/flink/pull/659
On Mon, May 11, 2015 at 6:29 PM, Stephan Ewen <se...@apache.org> wrote:
> Yep, I would say: Move ahead :-)
>
> On Tue, May 5, 2015 at 4:48 PM, Aljoscha Krettek <al...@apache.org>
> wrote:
>
>> So I gather I should go forward with this? If no-one objects I will
>> open a Jira and work on this.
>>
>> On Tue, May 5, 2015 at 4:14 PM, Aljoscha Krettek <al...@apache.org>
>> wrote:
>> > Yes, because the handling of punctuations depends on the operator: A
>> > MapOperator can just forward them while a windowed join or reduce can
>> > only forward them after emitting the correct windows or results.
>> >
>> > On Tue, May 5, 2015 at 3:58 PM, Paris Carbone <pa...@kth.se> wrote:
>> >> By watermark handling I meant making punctuations explicit and
>> forwarding/modifying them at the operator level. I think this is clear so
>> far.
>> >>> On 05 May 2015, at 15:41, Aljoscha Krettek <al...@apache.org>
>> wrote:
>> >>>
>> >>> There is no watermark handling yet. :D
>> >>>
>> >>> But this would enable me to do this.
>> >>>
>> >>> On Tue, May 5, 2015 at 3:39 PM, Paris Carbone <pa...@kth.se> wrote:
>> >>>> I agree with Gyula on this one. Barriers should better not be exposed
>> to the operator. They are system events for state management. Apart from
>> that, watermark handling seems to be on a right track, I like it so far.
>> >>>>
>> >>>>> On 05 May 2015, at 15:26, Aljoscha Krettek <al...@apache.org>
>> wrote:
>> >>>>>
>> >>>>> I don't know, I just put that there because other people are working
>> >>>>> on the checkpointing/barrier thing. So there would need to be some
>> >>>>> functionality there at some point.
>> >>>>>
>> >>>>> Or maybe it is not required there and can be handled in the
>> >>>>> StreamTask. Others might know this better than I do right now.
>> >>>>>
>> >>>>> On Tue, May 5, 2015 at 3:24 PM, Gyula Fóra <gy...@gmail.com>
>> wrote:
>> >>>>>> What would the processBarrier method do?
>> >>>>>>
>> >>>>>> On Tuesday, May 5, 2015, Aljoscha Krettek <al...@apache.org>
>> wrote:
>> >>>>>>
>> >>>>>>> I'm using the term punctuation and watermark interchangeably here
>> >>>>>>> because for practical purposes they do the same thing. I'm not sure
>> >>>>>>> what you meant with your comment about those.
>> >>>>>>>
>> >>>>>>> For the Operator interface I'm thinking about something like this:
>> >>>>>>>
>> >>>>>>> abstract class OneInputStreamOperator<IN, OUT, F extends
>> Function> {
>> >>>>>>> public processElement(IN element);
>> >>>>>>> public processBarrier(...);
>> >>>>>>> public processPunctuation/lowWatermark(...):
>> >>>>>>> }
>> >>>>>>>
>> >>>>>>> The operator also has access to the TaskContext and ExecutionConfig
>> >>>>>>> and Serializers. The operator would emit values using an emit()
>> method
>> >>>>>>> or the Collector interface, not sure about that yet.
>> >>>>>>>
>> >>>>>>> On Tue, May 5, 2015 at 3:12 PM, Gyula Fóra <gyfora@apache.org
>> >>>>>>> <javascript:;>> wrote:
>> >>>>>>>> I think this a good idea in general. I would try to minimize the
>> methods
>> >>>>>>> we
>> >>>>>>>> include and make the ones that we keep very concrete. For
>> instance i
>> >>>>>>> would
>> >>>>>>>> not have the receive barrier method as that is handled on a
>> totally
>> >>>>>>>> different level already. And instead of punctuation I would
>> directly add
>> >>>>>>> a
>> >>>>>>>> method to work on watermarks.
>> >>>>>>>>
>> >>>>>>>> On Tuesday, May 5, 2015, Aljoscha Krettek <aljoscha@apache.org
>> >>>>>>> <javascript:;>> wrote:
>> >>>>>>>>
>> >>>>>>>>> What do you mean by "losing iterations"?
>> >>>>>>>>>
>> >>>>>>>>> For the pros and cons:
>> >>>>>>>>>
>> >>>>>>>>> Cons: I can't think of any, since most of the operators are
>> chainable
>> >>>>>>>>> already and already behave like a collector.
>> >>>>>>>>>
>> >>>>>>>>> Pros:
>> >>>>>>>>> - Unified model for operators, chainable operators don't have to
>> >>>>>>>>> worry about input iterators and the collect interface.
>> >>>>>>>>> - Enables features that we want in the future, such as barriers
>> and
>> >>>>>>>>> punctuations because they don't work with the
>> >>>>>>>>> simple Collector interface.
>> >>>>>>>>> - The while-loop is moved outside of the operators, now the Task
>> (the
>> >>>>>>>>> thing that runs Operators) can control the flow of data better
>> and
>> >>>>>>>>> deal with
>> >>>>>>>>> stuff like barriers and punctuations. If we want to keep the
>> >>>>>>>>> main-loop inside each operator, then they all have to manage
>> input
>> >>>>>>>>> readers and inline events manually.
>> >>>>>>>>>
>> >>>>>>>>> On Tue, May 5, 2015 at 2:41 PM, Kostas Tzoumas <
>> ktzoumas@apache.org
>> >>>>>>> <javascript:;>
>> >>>>>>>>> <javascript:;>> wrote:
>> >>>>>>>>>> Can you give us a rough idea of the pros and cons? Do we lose
>> some
>> >>>>>>>>>> functionality by getting rid of iterations?
>> >>>>>>>>>>
>> >>>>>>>>>> Kostas
>> >>>>>>>>>>
>> >>>>>>>>>> On Tue, May 5, 2015 at 1:37 PM, Aljoscha Krettek <
>> aljoscha@apache.org
>> >>>>>>> <javascript:;>
>> >>>>>>>>> <javascript:;>>
>> >>>>>>>>>> wrote:
>> >>>>>>>>>>
>> >>>>>>>>>>> Hi Folks,
>> >>>>>>>>>>> while working on introducing source-assigned timestamps into
>> >>>>>>> streaming
>> >>>>>>>>>>> (https://issues.apache.org/jira/browse/FLINK-1967) I thought
>> about
>> >>>>>>> how
>> >>>>>>>>>>> the punctuations (low watermarks) can be pushed through the
>> system.
>> >>>>>>>>>>> The problem is, that operators can have two ways of getting
>> input: 1.
>> >>>>>>>>>>> They read directly from input iterators, and 2. They act as a
>> >>>>>>>>>>> Collector and get elements via collect() from the previous
>> operator
>> >>>>>>> in
>> >>>>>>>>>>> a chain.
>> >>>>>>>>>>>
>> >>>>>>>>>>> This makes it hard to push things through a chain that are not
>> >>>>>>>>>>> elements, such as barriers and/or punctuations.
>> >>>>>>>>>>>
>> >>>>>>>>>>> I propose to change all streaming operators to be push based,
>> with a
>> >>>>>>>>>>> slightly improved interface: In addition to collect(), which I
>> would
>> >>>>>>>>>>> call receiveElement() I would add receivePunctuation() and
>> >>>>>>>>>>> receiveBarrier(). The first operator in the chain would also
>> get data
>> >>>>>>>>>>> from the outside invokable that reads from the input iterator
>> and
>> >>>>>>>>>>> calls receiveElement() for the first operator in a chain.
>> >>>>>>>>>>>
>> >>>>>>>>>>> What do you think? I would of course be willing to implement
>> this
>> >>>>>>>>> myself.
>> >>>>>>>>>>>
>> >>>>>>>>>>> Cheers,
>> >>>>>>>>>>> Aljoscha
>> >>>>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>
>> >>>>
>> >>
>>
Re: [DISCUSS] Change Streaming Operators to be Push-Only
Posted by Stephan Ewen <se...@apache.org>.
Yep, I would say: Move ahead :-)
On Tue, May 5, 2015 at 4:48 PM, Aljoscha Krettek <al...@apache.org>
wrote:
> So I gather I should go forward with this? If no-one objects I will
> open a Jira and work on this.
>
> On Tue, May 5, 2015 at 4:14 PM, Aljoscha Krettek <al...@apache.org>
> wrote:
> > Yes, because the handling of punctuations depends on the operator: A
> > MapOperator can just forward them while a windowed join or reduce can
> > only forward them after emitting the correct windows or results.
> >
> > On Tue, May 5, 2015 at 3:58 PM, Paris Carbone <pa...@kth.se> wrote:
> >> By watermark handling I meant making punctuations explicit and
> forwarding/modifying them at the operator level. I think this is clear so
> far.
> >>> On 05 May 2015, at 15:41, Aljoscha Krettek <al...@apache.org>
> wrote:
> >>>
> >>> There is no watermark handling yet. :D
> >>>
> >>> But this would enable me to do this.
> >>>
> >>> On Tue, May 5, 2015 at 3:39 PM, Paris Carbone <pa...@kth.se> wrote:
> >>>> I agree with Gyula on this one. Barriers should better not be exposed
> to the operator. They are system events for state management. Apart from
> that, watermark handling seems to be on a right track, I like it so far.
> >>>>
> >>>>> On 05 May 2015, at 15:26, Aljoscha Krettek <al...@apache.org>
> wrote:
> >>>>>
> >>>>> I don't know, I just put that there because other people are working
> >>>>> on the checkpointing/barrier thing. So there would need to be some
> >>>>> functionality there at some point.
> >>>>>
> >>>>> Or maybe it is not required there and can be handled in the
> >>>>> StreamTask. Others might know this better than I do right now.
> >>>>>
> >>>>> On Tue, May 5, 2015 at 3:24 PM, Gyula Fóra <gy...@gmail.com>
> wrote:
> >>>>>> What would the processBarrier method do?
> >>>>>>
> >>>>>> On Tuesday, May 5, 2015, Aljoscha Krettek <al...@apache.org>
> wrote:
> >>>>>>
> >>>>>>> I'm using the term punctuation and watermark interchangeably here
> >>>>>>> because for practical purposes they do the same thing. I'm not sure
> >>>>>>> what you meant with your comment about those.
> >>>>>>>
> >>>>>>> For the Operator interface I'm thinking about something like this:
> >>>>>>>
> >>>>>>> abstract class OneInputStreamOperator<IN, OUT, F extends
> Function> {
> >>>>>>> public processElement(IN element);
> >>>>>>> public processBarrier(...);
> >>>>>>> public processPunctuation/lowWatermark(...):
> >>>>>>> }
> >>>>>>>
> >>>>>>> The operator also has access to the TaskContext and ExecutionConfig
> >>>>>>> and Serializers. The operator would emit values using an emit()
> method
> >>>>>>> or the Collector interface, not sure about that yet.
> >>>>>>>
> >>>>>>> On Tue, May 5, 2015 at 3:12 PM, Gyula Fóra <gyfora@apache.org
> >>>>>>> <javascript:;>> wrote:
> >>>>>>>> I think this a good idea in general. I would try to minimize the
> methods
> >>>>>>> we
> >>>>>>>> include and make the ones that we keep very concrete. For
> instance i
> >>>>>>> would
> >>>>>>>> not have the receive barrier method as that is handled on a
> totally
> >>>>>>>> different level already. And instead of punctuation I would
> directly add
> >>>>>>> a
> >>>>>>>> method to work on watermarks.
> >>>>>>>>
> >>>>>>>> On Tuesday, May 5, 2015, Aljoscha Krettek <aljoscha@apache.org
> >>>>>>> <javascript:;>> wrote:
> >>>>>>>>
> >>>>>>>>> What do you mean by "losing iterations"?
> >>>>>>>>>
> >>>>>>>>> For the pros and cons:
> >>>>>>>>>
> >>>>>>>>> Cons: I can't think of any, since most of the operators are
> chainable
> >>>>>>>>> already and already behave like a collector.
> >>>>>>>>>
> >>>>>>>>> Pros:
> >>>>>>>>> - Unified model for operators, chainable operators don't have to
> >>>>>>>>> worry about input iterators and the collect interface.
> >>>>>>>>> - Enables features that we want in the future, such as barriers
> and
> >>>>>>>>> punctuations because they don't work with the
> >>>>>>>>> simple Collector interface.
> >>>>>>>>> - The while-loop is moved outside of the operators, now the Task
> (the
> >>>>>>>>> thing that runs Operators) can control the flow of data better
> and
> >>>>>>>>> deal with
> >>>>>>>>> stuff like barriers and punctuations. If we want to keep the
> >>>>>>>>> main-loop inside each operator, then they all have to manage
> input
> >>>>>>>>> readers and inline events manually.
> >>>>>>>>>
> >>>>>>>>> On Tue, May 5, 2015 at 2:41 PM, Kostas Tzoumas <
> ktzoumas@apache.org
> >>>>>>> <javascript:;>
> >>>>>>>>> <javascript:;>> wrote:
> >>>>>>>>>> Can you give us a rough idea of the pros and cons? Do we lose
> some
> >>>>>>>>>> functionality by getting rid of iterations?
> >>>>>>>>>>
> >>>>>>>>>> Kostas
> >>>>>>>>>>
> >>>>>>>>>> On Tue, May 5, 2015 at 1:37 PM, Aljoscha Krettek <
> aljoscha@apache.org
> >>>>>>> <javascript:;>
> >>>>>>>>> <javascript:;>>
> >>>>>>>>>> wrote:
> >>>>>>>>>>
> >>>>>>>>>>> Hi Folks,
> >>>>>>>>>>> while working on introducing source-assigned timestamps into
> >>>>>>> streaming
> >>>>>>>>>>> (https://issues.apache.org/jira/browse/FLINK-1967) I thought
> about
> >>>>>>> how
> >>>>>>>>>>> the punctuations (low watermarks) can be pushed through the
> system.
> >>>>>>>>>>> The problem is, that operators can have two ways of getting
> input: 1.
> >>>>>>>>>>> They read directly from input iterators, and 2. They act as a
> >>>>>>>>>>> Collector and get elements via collect() from the previous
> operator
> >>>>>>> in
> >>>>>>>>>>> a chain.
> >>>>>>>>>>>
> >>>>>>>>>>> This makes it hard to push things through a chain that are not
> >>>>>>>>>>> elements, such as barriers and/or punctuations.
> >>>>>>>>>>>
> >>>>>>>>>>> I propose to change all streaming operators to be push based,
> with a
> >>>>>>>>>>> slightly improved interface: In addition to collect(), which I
> would
> >>>>>>>>>>> call receiveElement() I would add receivePunctuation() and
> >>>>>>>>>>> receiveBarrier(). The first operator in the chain would also
> get data
> >>>>>>>>>>> from the outside invokable that reads from the input iterator
> and
> >>>>>>>>>>> calls receiveElement() for the first operator in a chain.
> >>>>>>>>>>>
> >>>>>>>>>>> What do you think? I would of course be willing to implement
> this
> >>>>>>>>> myself.
> >>>>>>>>>>>
> >>>>>>>>>>> Cheers,
> >>>>>>>>>>> Aljoscha
> >>>>>>>>>>>
> >>>>>>>>>
> >>>>>>>
> >>>>
> >>
>
Re: [DISCUSS] Change Streaming Operators to be Push-Only
Posted by Aljoscha Krettek <al...@apache.org>.
So I gather I should go forward with this? If no-one objects I will
open a Jira and work on this.
On Tue, May 5, 2015 at 4:14 PM, Aljoscha Krettek <al...@apache.org> wrote:
> Yes, because the handling of punctuations depends on the operator: A
> MapOperator can just forward them while a windowed join or reduce can
> only forward them after emitting the correct windows or results.
>
> On Tue, May 5, 2015 at 3:58 PM, Paris Carbone <pa...@kth.se> wrote:
>> By watermark handling I meant making punctuations explicit and forwarding/modifying them at the operator level. I think this is clear so far.
>>> On 05 May 2015, at 15:41, Aljoscha Krettek <al...@apache.org> wrote:
>>>
>>> There is no watermark handling yet. :D
>>>
>>> But this would enable me to do this.
>>>
>>> On Tue, May 5, 2015 at 3:39 PM, Paris Carbone <pa...@kth.se> wrote:
>>>> I agree with Gyula on this one. Barriers should better not be exposed to the operator. They are system events for state management. Apart from that, watermark handling seems to be on a right track, I like it so far.
>>>>
>>>>> On 05 May 2015, at 15:26, Aljoscha Krettek <al...@apache.org> wrote:
>>>>>
>>>>> I don't know, I just put that there because other people are working
>>>>> on the checkpointing/barrier thing. So there would need to be some
>>>>> functionality there at some point.
>>>>>
>>>>> Or maybe it is not required there and can be handled in the
>>>>> StreamTask. Others might know this better than I do right now.
>>>>>
>>>>> On Tue, May 5, 2015 at 3:24 PM, Gyula Fóra <gy...@gmail.com> wrote:
>>>>>> What would the processBarrier method do?
>>>>>>
>>>>>> On Tuesday, May 5, 2015, Aljoscha Krettek <al...@apache.org> wrote:
>>>>>>
>>>>>>> I'm using the term punctuation and watermark interchangeably here
>>>>>>> because for practical purposes they do the same thing. I'm not sure
>>>>>>> what you meant with your comment about those.
>>>>>>>
>>>>>>> For the Operator interface I'm thinking about something like this:
>>>>>>>
>>>>>>> abstract class OneInputStreamOperator<IN, OUT, F extends Function> {
>>>>>>> public processElement(IN element);
>>>>>>> public processBarrier(...);
>>>>>>> public processPunctuation/lowWatermark(...):
>>>>>>> }
>>>>>>>
>>>>>>> The operator also has access to the TaskContext and ExecutionConfig
>>>>>>> and Serializers. The operator would emit values using an emit() method
>>>>>>> or the Collector interface, not sure about that yet.
>>>>>>>
>>>>>>> On Tue, May 5, 2015 at 3:12 PM, Gyula Fóra <gyfora@apache.org
>>>>>>> <javascript:;>> wrote:
>>>>>>>> I think this a good idea in general. I would try to minimize the methods
>>>>>>> we
>>>>>>>> include and make the ones that we keep very concrete. For instance i
>>>>>>> would
>>>>>>>> not have the receive barrier method as that is handled on a totally
>>>>>>>> different level already. And instead of punctuation I would directly add
>>>>>>> a
>>>>>>>> method to work on watermarks.
>>>>>>>>
>>>>>>>> On Tuesday, May 5, 2015, Aljoscha Krettek <aljoscha@apache.org
>>>>>>> <javascript:;>> wrote:
>>>>>>>>
>>>>>>>>> What do you mean by "losing iterations"?
>>>>>>>>>
>>>>>>>>> For the pros and cons:
>>>>>>>>>
>>>>>>>>> Cons: I can't think of any, since most of the operators are chainable
>>>>>>>>> already and already behave like a collector.
>>>>>>>>>
>>>>>>>>> Pros:
>>>>>>>>> - Unified model for operators, chainable operators don't have to
>>>>>>>>> worry about input iterators and the collect interface.
>>>>>>>>> - Enables features that we want in the future, such as barriers and
>>>>>>>>> punctuations because they don't work with the
>>>>>>>>> simple Collector interface.
>>>>>>>>> - The while-loop is moved outside of the operators, now the Task (the
>>>>>>>>> thing that runs Operators) can control the flow of data better and
>>>>>>>>> deal with
>>>>>>>>> stuff like barriers and punctuations. If we want to keep the
>>>>>>>>> main-loop inside each operator, then they all have to manage input
>>>>>>>>> readers and inline events manually.
>>>>>>>>>
>>>>>>>>> On Tue, May 5, 2015 at 2:41 PM, Kostas Tzoumas <ktzoumas@apache.org
>>>>>>> <javascript:;>
>>>>>>>>> <javascript:;>> wrote:
>>>>>>>>>> Can you give us a rough idea of the pros and cons? Do we lose some
>>>>>>>>>> functionality by getting rid of iterations?
>>>>>>>>>>
>>>>>>>>>> Kostas
>>>>>>>>>>
>>>>>>>>>> On Tue, May 5, 2015 at 1:37 PM, Aljoscha Krettek <aljoscha@apache.org
>>>>>>> <javascript:;>
>>>>>>>>> <javascript:;>>
>>>>>>>>>> wrote:
>>>>>>>>>>
>>>>>>>>>>> Hi Folks,
>>>>>>>>>>> while working on introducing source-assigned timestamps into
>>>>>>> streaming
>>>>>>>>>>> (https://issues.apache.org/jira/browse/FLINK-1967) I thought about
>>>>>>> how
>>>>>>>>>>> the punctuations (low watermarks) can be pushed through the system.
>>>>>>>>>>> The problem is, that operators can have two ways of getting input: 1.
>>>>>>>>>>> They read directly from input iterators, and 2. They act as a
>>>>>>>>>>> Collector and get elements via collect() from the previous operator
>>>>>>> in
>>>>>>>>>>> a chain.
>>>>>>>>>>>
>>>>>>>>>>> This makes it hard to push things through a chain that are not
>>>>>>>>>>> elements, such as barriers and/or punctuations.
>>>>>>>>>>>
>>>>>>>>>>> I propose to change all streaming operators to be push based, with a
>>>>>>>>>>> slightly improved interface: In addition to collect(), which I would
>>>>>>>>>>> call receiveElement() I would add receivePunctuation() and
>>>>>>>>>>> receiveBarrier(). The first operator in the chain would also get data
>>>>>>>>>>> from the outside invokable that reads from the input iterator and
>>>>>>>>>>> calls receiveElement() for the first operator in a chain.
>>>>>>>>>>>
>>>>>>>>>>> What do you think? I would of course be willing to implement this
>>>>>>>>> myself.
>>>>>>>>>>>
>>>>>>>>>>> Cheers,
>>>>>>>>>>> Aljoscha
>>>>>>>>>>>
>>>>>>>>>
>>>>>>>
>>>>
>>
Re: [DISCUSS] Change Streaming Operators to be Push-Only
Posted by Aljoscha Krettek <al...@apache.org>.
Yes, because the handling of punctuations depends on the operator: A
MapOperator can just forward them while a windowed join or reduce can
only forward them after emitting the correct windows or results.
On Tue, May 5, 2015 at 3:58 PM, Paris Carbone <pa...@kth.se> wrote:
> By watermark handling I meant making punctuations explicit and forwarding/modifying them at the operator level. I think this is clear so far.
>> On 05 May 2015, at 15:41, Aljoscha Krettek <al...@apache.org> wrote:
>>
>> There is no watermark handling yet. :D
>>
>> But this would enable me to do this.
>>
>> On Tue, May 5, 2015 at 3:39 PM, Paris Carbone <pa...@kth.se> wrote:
>>> I agree with Gyula on this one. Barriers should better not be exposed to the operator. They are system events for state management. Apart from that, watermark handling seems to be on a right track, I like it so far.
>>>
>>>> On 05 May 2015, at 15:26, Aljoscha Krettek <al...@apache.org> wrote:
>>>>
>>>> I don't know, I just put that there because other people are working
>>>> on the checkpointing/barrier thing. So there would need to be some
>>>> functionality there at some point.
>>>>
>>>> Or maybe it is not required there and can be handled in the
>>>> StreamTask. Others might know this better than I do right now.
>>>>
>>>> On Tue, May 5, 2015 at 3:24 PM, Gyula Fóra <gy...@gmail.com> wrote:
>>>>> What would the processBarrier method do?
>>>>>
>>>>> On Tuesday, May 5, 2015, Aljoscha Krettek <al...@apache.org> wrote:
>>>>>
>>>>>> I'm using the term punctuation and watermark interchangeably here
>>>>>> because for practical purposes they do the same thing. I'm not sure
>>>>>> what you meant with your comment about those.
>>>>>>
>>>>>> For the Operator interface I'm thinking about something like this:
>>>>>>
>>>>>> abstract class OneInputStreamOperator<IN, OUT, F extends Function> {
>>>>>> public processElement(IN element);
>>>>>> public processBarrier(...);
>>>>>> public processPunctuation/lowWatermark(...):
>>>>>> }
>>>>>>
>>>>>> The operator also has access to the TaskContext and ExecutionConfig
>>>>>> and Serializers. The operator would emit values using an emit() method
>>>>>> or the Collector interface, not sure about that yet.
>>>>>>
>>>>>> On Tue, May 5, 2015 at 3:12 PM, Gyula Fóra <gyfora@apache.org
>>>>>> <javascript:;>> wrote:
>>>>>>> I think this a good idea in general. I would try to minimize the methods
>>>>>> we
>>>>>>> include and make the ones that we keep very concrete. For instance i
>>>>>> would
>>>>>>> not have the receive barrier method as that is handled on a totally
>>>>>>> different level already. And instead of punctuation I would directly add
>>>>>> a
>>>>>>> method to work on watermarks.
>>>>>>>
>>>>>>> On Tuesday, May 5, 2015, Aljoscha Krettek <aljoscha@apache.org
>>>>>> <javascript:;>> wrote:
>>>>>>>
>>>>>>>> What do you mean by "losing iterations"?
>>>>>>>>
>>>>>>>> For the pros and cons:
>>>>>>>>
>>>>>>>> Cons: I can't think of any, since most of the operators are chainable
>>>>>>>> already and already behave like a collector.
>>>>>>>>
>>>>>>>> Pros:
>>>>>>>> - Unified model for operators, chainable operators don't have to
>>>>>>>> worry about input iterators and the collect interface.
>>>>>>>> - Enables features that we want in the future, such as barriers and
>>>>>>>> punctuations because they don't work with the
>>>>>>>> simple Collector interface.
>>>>>>>> - The while-loop is moved outside of the operators, now the Task (the
>>>>>>>> thing that runs Operators) can control the flow of data better and
>>>>>>>> deal with
>>>>>>>> stuff like barriers and punctuations. If we want to keep the
>>>>>>>> main-loop inside each operator, then they all have to manage input
>>>>>>>> readers and inline events manually.
>>>>>>>>
>>>>>>>> On Tue, May 5, 2015 at 2:41 PM, Kostas Tzoumas <ktzoumas@apache.org
>>>>>> <javascript:;>
>>>>>>>> <javascript:;>> wrote:
>>>>>>>>> Can you give us a rough idea of the pros and cons? Do we lose some
>>>>>>>>> functionality by getting rid of iterations?
>>>>>>>>>
>>>>>>>>> Kostas
>>>>>>>>>
>>>>>>>>> On Tue, May 5, 2015 at 1:37 PM, Aljoscha Krettek <aljoscha@apache.org
>>>>>> <javascript:;>
>>>>>>>> <javascript:;>>
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>> Hi Folks,
>>>>>>>>>> while working on introducing source-assigned timestamps into
>>>>>> streaming
>>>>>>>>>> (https://issues.apache.org/jira/browse/FLINK-1967) I thought about
>>>>>> how
>>>>>>>>>> the punctuations (low watermarks) can be pushed through the system.
>>>>>>>>>> The problem is, that operators can have two ways of getting input: 1.
>>>>>>>>>> They read directly from input iterators, and 2. They act as a
>>>>>>>>>> Collector and get elements via collect() from the previous operator
>>>>>> in
>>>>>>>>>> a chain.
>>>>>>>>>>
>>>>>>>>>> This makes it hard to push things through a chain that are not
>>>>>>>>>> elements, such as barriers and/or punctuations.
>>>>>>>>>>
>>>>>>>>>> I propose to change all streaming operators to be push based, with a
>>>>>>>>>> slightly improved interface: In addition to collect(), which I would
>>>>>>>>>> call receiveElement() I would add receivePunctuation() and
>>>>>>>>>> receiveBarrier(). The first operator in the chain would also get data
>>>>>>>>>> from the outside invokable that reads from the input iterator and
>>>>>>>>>> calls receiveElement() for the first operator in a chain.
>>>>>>>>>>
>>>>>>>>>> What do you think? I would of course be willing to implement this
>>>>>>>> myself.
>>>>>>>>>>
>>>>>>>>>> Cheers,
>>>>>>>>>> Aljoscha
>>>>>>>>>>
>>>>>>>>
>>>>>>
>>>
>
Re: [DISCUSS] Change Streaming Operators to be Push-Only
Posted by Paris Carbone <pa...@kth.se>.
By watermark handling I meant making punctuations explicit and forwarding/modifying them at the operator level. I think this is clear so far.
> On 05 May 2015, at 15:41, Aljoscha Krettek <al...@apache.org> wrote:
>
> There is no watermark handling yet. :D
>
> But this would enable me to do this.
>
> On Tue, May 5, 2015 at 3:39 PM, Paris Carbone <pa...@kth.se> wrote:
>> I agree with Gyula on this one. Barriers should better not be exposed to the operator. They are system events for state management. Apart from that, watermark handling seems to be on a right track, I like it so far.
>>
>>> On 05 May 2015, at 15:26, Aljoscha Krettek <al...@apache.org> wrote:
>>>
>>> I don't know, I just put that there because other people are working
>>> on the checkpointing/barrier thing. So there would need to be some
>>> functionality there at some point.
>>>
>>> Or maybe it is not required there and can be handled in the
>>> StreamTask. Others might know this better than I do right now.
>>>
>>> On Tue, May 5, 2015 at 3:24 PM, Gyula Fóra <gy...@gmail.com> wrote:
>>>> What would the processBarrier method do?
>>>>
>>>> On Tuesday, May 5, 2015, Aljoscha Krettek <al...@apache.org> wrote:
>>>>
>>>>> I'm using the term punctuation and watermark interchangeably here
>>>>> because for practical purposes they do the same thing. I'm not sure
>>>>> what you meant with your comment about those.
>>>>>
>>>>> For the Operator interface I'm thinking about something like this:
>>>>>
>>>>> abstract class OneInputStreamOperator<IN, OUT, F extends Function> {
>>>>> public processElement(IN element);
>>>>> public processBarrier(...);
>>>>> public processPunctuation/lowWatermark(...):
>>>>> }
>>>>>
>>>>> The operator also has access to the TaskContext and ExecutionConfig
>>>>> and Serializers. The operator would emit values using an emit() method
>>>>> or the Collector interface, not sure about that yet.
>>>>>
>>>>> On Tue, May 5, 2015 at 3:12 PM, Gyula Fóra <gyfora@apache.org
>>>>> <javascript:;>> wrote:
>>>>>> I think this a good idea in general. I would try to minimize the methods
>>>>> we
>>>>>> include and make the ones that we keep very concrete. For instance i
>>>>> would
>>>>>> not have the receive barrier method as that is handled on a totally
>>>>>> different level already. And instead of punctuation I would directly add
>>>>> a
>>>>>> method to work on watermarks.
>>>>>>
>>>>>> On Tuesday, May 5, 2015, Aljoscha Krettek <aljoscha@apache.org
>>>>> <javascript:;>> wrote:
>>>>>>
>>>>>>> What do you mean by "losing iterations"?
>>>>>>>
>>>>>>> For the pros and cons:
>>>>>>>
>>>>>>> Cons: I can't think of any, since most of the operators are chainable
>>>>>>> already and already behave like a collector.
>>>>>>>
>>>>>>> Pros:
>>>>>>> - Unified model for operators, chainable operators don't have to
>>>>>>> worry about input iterators and the collect interface.
>>>>>>> - Enables features that we want in the future, such as barriers and
>>>>>>> punctuations because they don't work with the
>>>>>>> simple Collector interface.
>>>>>>> - The while-loop is moved outside of the operators, now the Task (the
>>>>>>> thing that runs Operators) can control the flow of data better and
>>>>>>> deal with
>>>>>>> stuff like barriers and punctuations. If we want to keep the
>>>>>>> main-loop inside each operator, then they all have to manage input
>>>>>>> readers and inline events manually.
>>>>>>>
>>>>>>> On Tue, May 5, 2015 at 2:41 PM, Kostas Tzoumas <ktzoumas@apache.org
>>>>> <javascript:;>
>>>>>>> <javascript:;>> wrote:
>>>>>>>> Can you give us a rough idea of the pros and cons? Do we lose some
>>>>>>>> functionality by getting rid of iterations?
>>>>>>>>
>>>>>>>> Kostas
>>>>>>>>
>>>>>>>> On Tue, May 5, 2015 at 1:37 PM, Aljoscha Krettek <aljoscha@apache.org
>>>>> <javascript:;>
>>>>>>> <javascript:;>>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Hi Folks,
>>>>>>>>> while working on introducing source-assigned timestamps into
>>>>> streaming
>>>>>>>>> (https://issues.apache.org/jira/browse/FLINK-1967) I thought about
>>>>> how
>>>>>>>>> the punctuations (low watermarks) can be pushed through the system.
>>>>>>>>> The problem is, that operators can have two ways of getting input: 1.
>>>>>>>>> They read directly from input iterators, and 2. They act as a
>>>>>>>>> Collector and get elements via collect() from the previous operator
>>>>> in
>>>>>>>>> a chain.
>>>>>>>>>
>>>>>>>>> This makes it hard to push things through a chain that are not
>>>>>>>>> elements, such as barriers and/or punctuations.
>>>>>>>>>
>>>>>>>>> I propose to change all streaming operators to be push based, with a
>>>>>>>>> slightly improved interface: In addition to collect(), which I would
>>>>>>>>> call receiveElement() I would add receivePunctuation() and
>>>>>>>>> receiveBarrier(). The first operator in the chain would also get data
>>>>>>>>> from the outside invokable that reads from the input iterator and
>>>>>>>>> calls receiveElement() for the first operator in a chain.
>>>>>>>>>
>>>>>>>>> What do you think? I would of course be willing to implement this
>>>>>>> myself.
>>>>>>>>>
>>>>>>>>> Cheers,
>>>>>>>>> Aljoscha
>>>>>>>>>
>>>>>>>
>>>>>
>>
Re: [DISCUSS] Change Streaming Operators to be Push-Only
Posted by Stephan Ewen <se...@apache.org>.
Does the operator have to know about barriers actually?
My first intuition would be that the operator reacts to a barrier the same
way as to a punctuation/watermark.
The outside driver handles the barriers as follows
1) Punctuate operator
2) Draw operator state snapshot
3) send output barriers
4) confirm after snapshot write is complete
That way, the operator needs not deal with checkpointing, but only allow
the driver to draw a state snapshot.
On Tue, May 5, 2015 at 3:41 PM, Aljoscha Krettek <al...@apache.org>
wrote:
> There is no watermark handling yet. :D
>
> But this would enable me to do this.
>
> On Tue, May 5, 2015 at 3:39 PM, Paris Carbone <pa...@kth.se> wrote:
> > I agree with Gyula on this one. Barriers should better not be exposed to
> the operator. They are system events for state management. Apart from that,
> watermark handling seems to be on a right track, I like it so far.
> >
> >> On 05 May 2015, at 15:26, Aljoscha Krettek <al...@apache.org> wrote:
> >>
> >> I don't know, I just put that there because other people are working
> >> on the checkpointing/barrier thing. So there would need to be some
> >> functionality there at some point.
> >>
> >> Or maybe it is not required there and can be handled in the
> >> StreamTask. Others might know this better than I do right now.
> >>
> >> On Tue, May 5, 2015 at 3:24 PM, Gyula Fóra <gy...@gmail.com>
> wrote:
> >>> What would the processBarrier method do?
> >>>
> >>> On Tuesday, May 5, 2015, Aljoscha Krettek <al...@apache.org> wrote:
> >>>
> >>>> I'm using the term punctuation and watermark interchangeably here
> >>>> because for practical purposes they do the same thing. I'm not sure
> >>>> what you meant with your comment about those.
> >>>>
> >>>> For the Operator interface I'm thinking about something like this:
> >>>>
> >>>> abstract class OneInputStreamOperator<IN, OUT, F extends Function> {
> >>>> public processElement(IN element);
> >>>> public processBarrier(...);
> >>>> public processPunctuation/lowWatermark(...):
> >>>> }
> >>>>
> >>>> The operator also has access to the TaskContext and ExecutionConfig
> >>>> and Serializers. The operator would emit values using an emit() method
> >>>> or the Collector interface, not sure about that yet.
> >>>>
> >>>> On Tue, May 5, 2015 at 3:12 PM, Gyula Fóra <gyfora@apache.org
> >>>> <javascript:;>> wrote:
> >>>>> I think this a good idea in general. I would try to minimize the
> methods
> >>>> we
> >>>>> include and make the ones that we keep very concrete. For instance i
> >>>> would
> >>>>> not have the receive barrier method as that is handled on a totally
> >>>>> different level already. And instead of punctuation I would directly
> add
> >>>> a
> >>>>> method to work on watermarks.
> >>>>>
> >>>>> On Tuesday, May 5, 2015, Aljoscha Krettek <aljoscha@apache.org
> >>>> <javascript:;>> wrote:
> >>>>>
> >>>>>> What do you mean by "losing iterations"?
> >>>>>>
> >>>>>> For the pros and cons:
> >>>>>>
> >>>>>> Cons: I can't think of any, since most of the operators are
> chainable
> >>>>>> already and already behave like a collector.
> >>>>>>
> >>>>>> Pros:
> >>>>>> - Unified model for operators, chainable operators don't have to
> >>>>>> worry about input iterators and the collect interface.
> >>>>>> - Enables features that we want in the future, such as barriers and
> >>>>>> punctuations because they don't work with the
> >>>>>> simple Collector interface.
> >>>>>> - The while-loop is moved outside of the operators, now the Task
> (the
> >>>>>> thing that runs Operators) can control the flow of data better and
> >>>>>> deal with
> >>>>>> stuff like barriers and punctuations. If we want to keep the
> >>>>>> main-loop inside each operator, then they all have to manage input
> >>>>>> readers and inline events manually.
> >>>>>>
> >>>>>> On Tue, May 5, 2015 at 2:41 PM, Kostas Tzoumas <ktzoumas@apache.org
> >>>> <javascript:;>
> >>>>>> <javascript:;>> wrote:
> >>>>>>> Can you give us a rough idea of the pros and cons? Do we lose some
> >>>>>>> functionality by getting rid of iterations?
> >>>>>>>
> >>>>>>> Kostas
> >>>>>>>
> >>>>>>> On Tue, May 5, 2015 at 1:37 PM, Aljoscha Krettek <
> aljoscha@apache.org
> >>>> <javascript:;>
> >>>>>> <javascript:;>>
> >>>>>>> wrote:
> >>>>>>>
> >>>>>>>> Hi Folks,
> >>>>>>>> while working on introducing source-assigned timestamps into
> >>>> streaming
> >>>>>>>> (https://issues.apache.org/jira/browse/FLINK-1967) I thought
> about
> >>>> how
> >>>>>>>> the punctuations (low watermarks) can be pushed through the
> system.
> >>>>>>>> The problem is, that operators can have two ways of getting
> input: 1.
> >>>>>>>> They read directly from input iterators, and 2. They act as a
> >>>>>>>> Collector and get elements via collect() from the previous
> operator
> >>>> in
> >>>>>>>> a chain.
> >>>>>>>>
> >>>>>>>> This makes it hard to push things through a chain that are not
> >>>>>>>> elements, such as barriers and/or punctuations.
> >>>>>>>>
> >>>>>>>> I propose to change all streaming operators to be push based,
> with a
> >>>>>>>> slightly improved interface: In addition to collect(), which I
> would
> >>>>>>>> call receiveElement() I would add receivePunctuation() and
> >>>>>>>> receiveBarrier(). The first operator in the chain would also get
> data
> >>>>>>>> from the outside invokable that reads from the input iterator and
> >>>>>>>> calls receiveElement() for the first operator in a chain.
> >>>>>>>>
> >>>>>>>> What do you think? I would of course be willing to implement this
> >>>>>> myself.
> >>>>>>>>
> >>>>>>>> Cheers,
> >>>>>>>> Aljoscha
> >>>>>>>>
> >>>>>>
> >>>>
> >
>
Re: [DISCUSS] Change Streaming Operators to be Push-Only
Posted by Aljoscha Krettek <al...@apache.org>.
There is no watermark handling yet. :D
But this would enable me to do this.
On Tue, May 5, 2015 at 3:39 PM, Paris Carbone <pa...@kth.se> wrote:
> I agree with Gyula on this one. Barriers should better not be exposed to the operator. They are system events for state management. Apart from that, watermark handling seems to be on a right track, I like it so far.
>
>> On 05 May 2015, at 15:26, Aljoscha Krettek <al...@apache.org> wrote:
>>
>> I don't know, I just put that there because other people are working
>> on the checkpointing/barrier thing. So there would need to be some
>> functionality there at some point.
>>
>> Or maybe it is not required there and can be handled in the
>> StreamTask. Others might know this better than I do right now.
>>
>> On Tue, May 5, 2015 at 3:24 PM, Gyula Fóra <gy...@gmail.com> wrote:
>>> What would the processBarrier method do?
>>>
>>> On Tuesday, May 5, 2015, Aljoscha Krettek <al...@apache.org> wrote:
>>>
>>>> I'm using the term punctuation and watermark interchangeably here
>>>> because for practical purposes they do the same thing. I'm not sure
>>>> what you meant with your comment about those.
>>>>
>>>> For the Operator interface I'm thinking about something like this:
>>>>
>>>> abstract class OneInputStreamOperator<IN, OUT, F extends Function> {
>>>> public processElement(IN element);
>>>> public processBarrier(...);
>>>> public processPunctuation/lowWatermark(...):
>>>> }
>>>>
>>>> The operator also has access to the TaskContext and ExecutionConfig
>>>> and Serializers. The operator would emit values using an emit() method
>>>> or the Collector interface, not sure about that yet.
>>>>
>>>> On Tue, May 5, 2015 at 3:12 PM, Gyula Fóra <gyfora@apache.org
>>>> <javascript:;>> wrote:
>>>>> I think this a good idea in general. I would try to minimize the methods
>>>> we
>>>>> include and make the ones that we keep very concrete. For instance i
>>>> would
>>>>> not have the receive barrier method as that is handled on a totally
>>>>> different level already. And instead of punctuation I would directly add
>>>> a
>>>>> method to work on watermarks.
>>>>>
>>>>> On Tuesday, May 5, 2015, Aljoscha Krettek <aljoscha@apache.org
>>>> <javascript:;>> wrote:
>>>>>
>>>>>> What do you mean by "losing iterations"?
>>>>>>
>>>>>> For the pros and cons:
>>>>>>
>>>>>> Cons: I can't think of any, since most of the operators are chainable
>>>>>> already and already behave like a collector.
>>>>>>
>>>>>> Pros:
>>>>>> - Unified model for operators, chainable operators don't have to
>>>>>> worry about input iterators and the collect interface.
>>>>>> - Enables features that we want in the future, such as barriers and
>>>>>> punctuations because they don't work with the
>>>>>> simple Collector interface.
>>>>>> - The while-loop is moved outside of the operators, now the Task (the
>>>>>> thing that runs Operators) can control the flow of data better and
>>>>>> deal with
>>>>>> stuff like barriers and punctuations. If we want to keep the
>>>>>> main-loop inside each operator, then they all have to manage input
>>>>>> readers and inline events manually.
>>>>>>
>>>>>> On Tue, May 5, 2015 at 2:41 PM, Kostas Tzoumas <ktzoumas@apache.org
>>>> <javascript:;>
>>>>>> <javascript:;>> wrote:
>>>>>>> Can you give us a rough idea of the pros and cons? Do we lose some
>>>>>>> functionality by getting rid of iterations?
>>>>>>>
>>>>>>> Kostas
>>>>>>>
>>>>>>> On Tue, May 5, 2015 at 1:37 PM, Aljoscha Krettek <aljoscha@apache.org
>>>> <javascript:;>
>>>>>> <javascript:;>>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Hi Folks,
>>>>>>>> while working on introducing source-assigned timestamps into
>>>> streaming
>>>>>>>> (https://issues.apache.org/jira/browse/FLINK-1967) I thought about
>>>> how
>>>>>>>> the punctuations (low watermarks) can be pushed through the system.
>>>>>>>> The problem is, that operators can have two ways of getting input: 1.
>>>>>>>> They read directly from input iterators, and 2. They act as a
>>>>>>>> Collector and get elements via collect() from the previous operator
>>>> in
>>>>>>>> a chain.
>>>>>>>>
>>>>>>>> This makes it hard to push things through a chain that are not
>>>>>>>> elements, such as barriers and/or punctuations.
>>>>>>>>
>>>>>>>> I propose to change all streaming operators to be push based, with a
>>>>>>>> slightly improved interface: In addition to collect(), which I would
>>>>>>>> call receiveElement() I would add receivePunctuation() and
>>>>>>>> receiveBarrier(). The first operator in the chain would also get data
>>>>>>>> from the outside invokable that reads from the input iterator and
>>>>>>>> calls receiveElement() for the first operator in a chain.
>>>>>>>>
>>>>>>>> What do you think? I would of course be willing to implement this
>>>>>> myself.
>>>>>>>>
>>>>>>>> Cheers,
>>>>>>>> Aljoscha
>>>>>>>>
>>>>>>
>>>>
>
Re: [DISCUSS] Change Streaming Operators to be Push-Only
Posted by Paris Carbone <pa...@kth.se>.
I agree with Gyula on this one. Barriers should better not be exposed to the operator. They are system events for state management. Apart from that, watermark handling seems to be on a right track, I like it so far.
> On 05 May 2015, at 15:26, Aljoscha Krettek <al...@apache.org> wrote:
>
> I don't know, I just put that there because other people are working
> on the checkpointing/barrier thing. So there would need to be some
> functionality there at some point.
>
> Or maybe it is not required there and can be handled in the
> StreamTask. Others might know this better than I do right now.
>
> On Tue, May 5, 2015 at 3:24 PM, Gyula Fóra <gy...@gmail.com> wrote:
>> What would the processBarrier method do?
>>
>> On Tuesday, May 5, 2015, Aljoscha Krettek <al...@apache.org> wrote:
>>
>>> I'm using the term punctuation and watermark interchangeably here
>>> because for practical purposes they do the same thing. I'm not sure
>>> what you meant with your comment about those.
>>>
>>> For the Operator interface I'm thinking about something like this:
>>>
>>> abstract class OneInputStreamOperator<IN, OUT, F extends Function> {
>>> public processElement(IN element);
>>> public processBarrier(...);
>>> public processPunctuation/lowWatermark(...):
>>> }
>>>
>>> The operator also has access to the TaskContext and ExecutionConfig
>>> and Serializers. The operator would emit values using an emit() method
>>> or the Collector interface, not sure about that yet.
>>>
>>> On Tue, May 5, 2015 at 3:12 PM, Gyula Fóra <gyfora@apache.org
>>> <javascript:;>> wrote:
>>>> I think this a good idea in general. I would try to minimize the methods
>>> we
>>>> include and make the ones that we keep very concrete. For instance i
>>> would
>>>> not have the receive barrier method as that is handled on a totally
>>>> different level already. And instead of punctuation I would directly add
>>> a
>>>> method to work on watermarks.
>>>>
>>>> On Tuesday, May 5, 2015, Aljoscha Krettek <aljoscha@apache.org
>>> <javascript:;>> wrote:
>>>>
>>>>> What do you mean by "losing iterations"?
>>>>>
>>>>> For the pros and cons:
>>>>>
>>>>> Cons: I can't think of any, since most of the operators are chainable
>>>>> already and already behave like a collector.
>>>>>
>>>>> Pros:
>>>>> - Unified model for operators, chainable operators don't have to
>>>>> worry about input iterators and the collect interface.
>>>>> - Enables features that we want in the future, such as barriers and
>>>>> punctuations because they don't work with the
>>>>> simple Collector interface.
>>>>> - The while-loop is moved outside of the operators, now the Task (the
>>>>> thing that runs Operators) can control the flow of data better and
>>>>> deal with
>>>>> stuff like barriers and punctuations. If we want to keep the
>>>>> main-loop inside each operator, then they all have to manage input
>>>>> readers and inline events manually.
>>>>>
>>>>> On Tue, May 5, 2015 at 2:41 PM, Kostas Tzoumas <ktzoumas@apache.org
>>> <javascript:;>
>>>>> <javascript:;>> wrote:
>>>>>> Can you give us a rough idea of the pros and cons? Do we lose some
>>>>>> functionality by getting rid of iterations?
>>>>>>
>>>>>> Kostas
>>>>>>
>>>>>> On Tue, May 5, 2015 at 1:37 PM, Aljoscha Krettek <aljoscha@apache.org
>>> <javascript:;>
>>>>> <javascript:;>>
>>>>>> wrote:
>>>>>>
>>>>>>> Hi Folks,
>>>>>>> while working on introducing source-assigned timestamps into
>>> streaming
>>>>>>> (https://issues.apache.org/jira/browse/FLINK-1967) I thought about
>>> how
>>>>>>> the punctuations (low watermarks) can be pushed through the system.
>>>>>>> The problem is, that operators can have two ways of getting input: 1.
>>>>>>> They read directly from input iterators, and 2. They act as a
>>>>>>> Collector and get elements via collect() from the previous operator
>>> in
>>>>>>> a chain.
>>>>>>>
>>>>>>> This makes it hard to push things through a chain that are not
>>>>>>> elements, such as barriers and/or punctuations.
>>>>>>>
>>>>>>> I propose to change all streaming operators to be push based, with a
>>>>>>> slightly improved interface: In addition to collect(), which I would
>>>>>>> call receiveElement() I would add receivePunctuation() and
>>>>>>> receiveBarrier(). The first operator in the chain would also get data
>>>>>>> from the outside invokable that reads from the input iterator and
>>>>>>> calls receiveElement() for the first operator in a chain.
>>>>>>>
>>>>>>> What do you think? I would of course be willing to implement this
>>>>> myself.
>>>>>>>
>>>>>>> Cheers,
>>>>>>> Aljoscha
>>>>>>>
>>>>>
>>>
Re: [DISCUSS] Change Streaming Operators to be Push-Only
Posted by Gyula Fóra <gy...@gmail.com>.
Yes, we dont need that method there. Snapshots are handled as a call to the
streamtask from the input reader.
On Tuesday, May 5, 2015, Aljoscha Krettek <al...@apache.org> wrote:
> I don't know, I just put that there because other people are working
> on the checkpointing/barrier thing. So there would need to be some
> functionality there at some point.
>
> Or maybe it is not required there and can be handled in the
> StreamTask. Others might know this better than I do right now.
>
> On Tue, May 5, 2015 at 3:24 PM, Gyula Fóra <gyula.fora@gmail.com
> <javascript:;>> wrote:
> > What would the processBarrier method do?
> >
> > On Tuesday, May 5, 2015, Aljoscha Krettek <aljoscha@apache.org
> <javascript:;>> wrote:
> >
> >> I'm using the term punctuation and watermark interchangeably here
> >> because for practical purposes they do the same thing. I'm not sure
> >> what you meant with your comment about those.
> >>
> >> For the Operator interface I'm thinking about something like this:
> >>
> >> abstract class OneInputStreamOperator<IN, OUT, F extends Function> {
> >> public processElement(IN element);
> >> public processBarrier(...);
> >> public processPunctuation/lowWatermark(...):
> >> }
> >>
> >> The operator also has access to the TaskContext and ExecutionConfig
> >> and Serializers. The operator would emit values using an emit() method
> >> or the Collector interface, not sure about that yet.
> >>
> >> On Tue, May 5, 2015 at 3:12 PM, Gyula Fóra <gyfora@apache.org
> <javascript:;>
> >> <javascript:;>> wrote:
> >> > I think this a good idea in general. I would try to minimize the
> methods
> >> we
> >> > include and make the ones that we keep very concrete. For instance i
> >> would
> >> > not have the receive barrier method as that is handled on a totally
> >> > different level already. And instead of punctuation I would directly
> add
> >> a
> >> > method to work on watermarks.
> >> >
> >> > On Tuesday, May 5, 2015, Aljoscha Krettek <aljoscha@apache.org
> <javascript:;>
> >> <javascript:;>> wrote:
> >> >
> >> >> What do you mean by "losing iterations"?
> >> >>
> >> >> For the pros and cons:
> >> >>
> >> >> Cons: I can't think of any, since most of the operators are chainable
> >> >> already and already behave like a collector.
> >> >>
> >> >> Pros:
> >> >> - Unified model for operators, chainable operators don't have to
> >> >> worry about input iterators and the collect interface.
> >> >> - Enables features that we want in the future, such as barriers and
> >> >> punctuations because they don't work with the
> >> >> simple Collector interface.
> >> >> - The while-loop is moved outside of the operators, now the Task
> (the
> >> >> thing that runs Operators) can control the flow of data better and
> >> >> deal with
> >> >> stuff like barriers and punctuations. If we want to keep the
> >> >> main-loop inside each operator, then they all have to manage input
> >> >> readers and inline events manually.
> >> >>
> >> >> On Tue, May 5, 2015 at 2:41 PM, Kostas Tzoumas <ktzoumas@apache.org
> <javascript:;>
> >> <javascript:;>
> >> >> <javascript:;>> wrote:
> >> >> > Can you give us a rough idea of the pros and cons? Do we lose some
> >> >> > functionality by getting rid of iterations?
> >> >> >
> >> >> > Kostas
> >> >> >
> >> >> > On Tue, May 5, 2015 at 1:37 PM, Aljoscha Krettek <
> aljoscha@apache.org <javascript:;>
> >> <javascript:;>
> >> >> <javascript:;>>
> >> >> > wrote:
> >> >> >
> >> >> >> Hi Folks,
> >> >> >> while working on introducing source-assigned timestamps into
> >> streaming
> >> >> >> (https://issues.apache.org/jira/browse/FLINK-1967) I thought
> about
> >> how
> >> >> >> the punctuations (low watermarks) can be pushed through the
> system.
> >> >> >> The problem is, that operators can have two ways of getting
> input: 1.
> >> >> >> They read directly from input iterators, and 2. They act as a
> >> >> >> Collector and get elements via collect() from the previous
> operator
> >> in
> >> >> >> a chain.
> >> >> >>
> >> >> >> This makes it hard to push things through a chain that are not
> >> >> >> elements, such as barriers and/or punctuations.
> >> >> >>
> >> >> >> I propose to change all streaming operators to be push based,
> with a
> >> >> >> slightly improved interface: In addition to collect(), which I
> would
> >> >> >> call receiveElement() I would add receivePunctuation() and
> >> >> >> receiveBarrier(). The first operator in the chain would also get
> data
> >> >> >> from the outside invokable that reads from the input iterator and
> >> >> >> calls receiveElement() for the first operator in a chain.
> >> >> >>
> >> >> >> What do you think? I would of course be willing to implement this
> >> >> myself.
> >> >> >>
> >> >> >> Cheers,
> >> >> >> Aljoscha
> >> >> >>
> >> >>
> >>
>
Re: [DISCUSS] Change Streaming Operators to be Push-Only
Posted by Aljoscha Krettek <al...@apache.org>.
I don't know, I just put that there because other people are working
on the checkpointing/barrier thing. So there would need to be some
functionality there at some point.
Or maybe it is not required there and can be handled in the
StreamTask. Others might know this better than I do right now.
On Tue, May 5, 2015 at 3:24 PM, Gyula Fóra <gy...@gmail.com> wrote:
> What would the processBarrier method do?
>
> On Tuesday, May 5, 2015, Aljoscha Krettek <al...@apache.org> wrote:
>
>> I'm using the term punctuation and watermark interchangeably here
>> because for practical purposes they do the same thing. I'm not sure
>> what you meant with your comment about those.
>>
>> For the Operator interface I'm thinking about something like this:
>>
>> abstract class OneInputStreamOperator<IN, OUT, F extends Function> {
>> public processElement(IN element);
>> public processBarrier(...);
>> public processPunctuation/lowWatermark(...):
>> }
>>
>> The operator also has access to the TaskContext and ExecutionConfig
>> and Serializers. The operator would emit values using an emit() method
>> or the Collector interface, not sure about that yet.
>>
>> On Tue, May 5, 2015 at 3:12 PM, Gyula Fóra <gyfora@apache.org
>> <javascript:;>> wrote:
>> > I think this a good idea in general. I would try to minimize the methods
>> we
>> > include and make the ones that we keep very concrete. For instance i
>> would
>> > not have the receive barrier method as that is handled on a totally
>> > different level already. And instead of punctuation I would directly add
>> a
>> > method to work on watermarks.
>> >
>> > On Tuesday, May 5, 2015, Aljoscha Krettek <aljoscha@apache.org
>> <javascript:;>> wrote:
>> >
>> >> What do you mean by "losing iterations"?
>> >>
>> >> For the pros and cons:
>> >>
>> >> Cons: I can't think of any, since most of the operators are chainable
>> >> already and already behave like a collector.
>> >>
>> >> Pros:
>> >> - Unified model for operators, chainable operators don't have to
>> >> worry about input iterators and the collect interface.
>> >> - Enables features that we want in the future, such as barriers and
>> >> punctuations because they don't work with the
>> >> simple Collector interface.
>> >> - The while-loop is moved outside of the operators, now the Task (the
>> >> thing that runs Operators) can control the flow of data better and
>> >> deal with
>> >> stuff like barriers and punctuations. If we want to keep the
>> >> main-loop inside each operator, then they all have to manage input
>> >> readers and inline events manually.
>> >>
>> >> On Tue, May 5, 2015 at 2:41 PM, Kostas Tzoumas <ktzoumas@apache.org
>> <javascript:;>
>> >> <javascript:;>> wrote:
>> >> > Can you give us a rough idea of the pros and cons? Do we lose some
>> >> > functionality by getting rid of iterations?
>> >> >
>> >> > Kostas
>> >> >
>> >> > On Tue, May 5, 2015 at 1:37 PM, Aljoscha Krettek <aljoscha@apache.org
>> <javascript:;>
>> >> <javascript:;>>
>> >> > wrote:
>> >> >
>> >> >> Hi Folks,
>> >> >> while working on introducing source-assigned timestamps into
>> streaming
>> >> >> (https://issues.apache.org/jira/browse/FLINK-1967) I thought about
>> how
>> >> >> the punctuations (low watermarks) can be pushed through the system.
>> >> >> The problem is, that operators can have two ways of getting input: 1.
>> >> >> They read directly from input iterators, and 2. They act as a
>> >> >> Collector and get elements via collect() from the previous operator
>> in
>> >> >> a chain.
>> >> >>
>> >> >> This makes it hard to push things through a chain that are not
>> >> >> elements, such as barriers and/or punctuations.
>> >> >>
>> >> >> I propose to change all streaming operators to be push based, with a
>> >> >> slightly improved interface: In addition to collect(), which I would
>> >> >> call receiveElement() I would add receivePunctuation() and
>> >> >> receiveBarrier(). The first operator in the chain would also get data
>> >> >> from the outside invokable that reads from the input iterator and
>> >> >> calls receiveElement() for the first operator in a chain.
>> >> >>
>> >> >> What do you think? I would of course be willing to implement this
>> >> myself.
>> >> >>
>> >> >> Cheers,
>> >> >> Aljoscha
>> >> >>
>> >>
>>
Re: [DISCUSS] Change Streaming Operators to be Push-Only
Posted by Gyula Fóra <gy...@gmail.com>.
What would the processBarrier method do?
On Tuesday, May 5, 2015, Aljoscha Krettek <al...@apache.org> wrote:
> I'm using the term punctuation and watermark interchangeably here
> because for practical purposes they do the same thing. I'm not sure
> what you meant with your comment about those.
>
> For the Operator interface I'm thinking about something like this:
>
> abstract class OneInputStreamOperator<IN, OUT, F extends Function> {
> public processElement(IN element);
> public processBarrier(...);
> public processPunctuation/lowWatermark(...):
> }
>
> The operator also has access to the TaskContext and ExecutionConfig
> and Serializers. The operator would emit values using an emit() method
> or the Collector interface, not sure about that yet.
>
> On Tue, May 5, 2015 at 3:12 PM, Gyula Fóra <gyfora@apache.org
> <javascript:;>> wrote:
> > I think this a good idea in general. I would try to minimize the methods
> we
> > include and make the ones that we keep very concrete. For instance i
> would
> > not have the receive barrier method as that is handled on a totally
> > different level already. And instead of punctuation I would directly add
> a
> > method to work on watermarks.
> >
> > On Tuesday, May 5, 2015, Aljoscha Krettek <aljoscha@apache.org
> <javascript:;>> wrote:
> >
> >> What do you mean by "losing iterations"?
> >>
> >> For the pros and cons:
> >>
> >> Cons: I can't think of any, since most of the operators are chainable
> >> already and already behave like a collector.
> >>
> >> Pros:
> >> - Unified model for operators, chainable operators don't have to
> >> worry about input iterators and the collect interface.
> >> - Enables features that we want in the future, such as barriers and
> >> punctuations because they don't work with the
> >> simple Collector interface.
> >> - The while-loop is moved outside of the operators, now the Task (the
> >> thing that runs Operators) can control the flow of data better and
> >> deal with
> >> stuff like barriers and punctuations. If we want to keep the
> >> main-loop inside each operator, then they all have to manage input
> >> readers and inline events manually.
> >>
> >> On Tue, May 5, 2015 at 2:41 PM, Kostas Tzoumas <ktzoumas@apache.org
> <javascript:;>
> >> <javascript:;>> wrote:
> >> > Can you give us a rough idea of the pros and cons? Do we lose some
> >> > functionality by getting rid of iterations?
> >> >
> >> > Kostas
> >> >
> >> > On Tue, May 5, 2015 at 1:37 PM, Aljoscha Krettek <aljoscha@apache.org
> <javascript:;>
> >> <javascript:;>>
> >> > wrote:
> >> >
> >> >> Hi Folks,
> >> >> while working on introducing source-assigned timestamps into
> streaming
> >> >> (https://issues.apache.org/jira/browse/FLINK-1967) I thought about
> how
> >> >> the punctuations (low watermarks) can be pushed through the system.
> >> >> The problem is, that operators can have two ways of getting input: 1.
> >> >> They read directly from input iterators, and 2. They act as a
> >> >> Collector and get elements via collect() from the previous operator
> in
> >> >> a chain.
> >> >>
> >> >> This makes it hard to push things through a chain that are not
> >> >> elements, such as barriers and/or punctuations.
> >> >>
> >> >> I propose to change all streaming operators to be push based, with a
> >> >> slightly improved interface: In addition to collect(), which I would
> >> >> call receiveElement() I would add receivePunctuation() and
> >> >> receiveBarrier(). The first operator in the chain would also get data
> >> >> from the outside invokable that reads from the input iterator and
> >> >> calls receiveElement() for the first operator in a chain.
> >> >>
> >> >> What do you think? I would of course be willing to implement this
> >> myself.
> >> >>
> >> >> Cheers,
> >> >> Aljoscha
> >> >>
> >>
>
Re: [DISCUSS] Change Streaming Operators to be Push-Only
Posted by Aljoscha Krettek <al...@apache.org>.
I'm using the term punctuation and watermark interchangeably here
because for practical purposes they do the same thing. I'm not sure
what you meant with your comment about those.
For the Operator interface I'm thinking about something like this:
abstract class OneInputStreamOperator<IN, OUT, F extends Function> {
public processElement(IN element);
public processBarrier(...);
public processPunctuation/lowWatermark(...):
}
The operator also has access to the TaskContext and ExecutionConfig
and Serializers. The operator would emit values using an emit() method
or the Collector interface, not sure about that yet.
On Tue, May 5, 2015 at 3:12 PM, Gyula Fóra <gy...@apache.org> wrote:
> I think this a good idea in general. I would try to minimize the methods we
> include and make the ones that we keep very concrete. For instance i would
> not have the receive barrier method as that is handled on a totally
> different level already. And instead of punctuation I would directly add a
> method to work on watermarks.
>
> On Tuesday, May 5, 2015, Aljoscha Krettek <al...@apache.org> wrote:
>
>> What do you mean by "losing iterations"?
>>
>> For the pros and cons:
>>
>> Cons: I can't think of any, since most of the operators are chainable
>> already and already behave like a collector.
>>
>> Pros:
>> - Unified model for operators, chainable operators don't have to
>> worry about input iterators and the collect interface.
>> - Enables features that we want in the future, such as barriers and
>> punctuations because they don't work with the
>> simple Collector interface.
>> - The while-loop is moved outside of the operators, now the Task (the
>> thing that runs Operators) can control the flow of data better and
>> deal with
>> stuff like barriers and punctuations. If we want to keep the
>> main-loop inside each operator, then they all have to manage input
>> readers and inline events manually.
>>
>> On Tue, May 5, 2015 at 2:41 PM, Kostas Tzoumas <ktzoumas@apache.org
>> <javascript:;>> wrote:
>> > Can you give us a rough idea of the pros and cons? Do we lose some
>> > functionality by getting rid of iterations?
>> >
>> > Kostas
>> >
>> > On Tue, May 5, 2015 at 1:37 PM, Aljoscha Krettek <aljoscha@apache.org
>> <javascript:;>>
>> > wrote:
>> >
>> >> Hi Folks,
>> >> while working on introducing source-assigned timestamps into streaming
>> >> (https://issues.apache.org/jira/browse/FLINK-1967) I thought about how
>> >> the punctuations (low watermarks) can be pushed through the system.
>> >> The problem is, that operators can have two ways of getting input: 1.
>> >> They read directly from input iterators, and 2. They act as a
>> >> Collector and get elements via collect() from the previous operator in
>> >> a chain.
>> >>
>> >> This makes it hard to push things through a chain that are not
>> >> elements, such as barriers and/or punctuations.
>> >>
>> >> I propose to change all streaming operators to be push based, with a
>> >> slightly improved interface: In addition to collect(), which I would
>> >> call receiveElement() I would add receivePunctuation() and
>> >> receiveBarrier(). The first operator in the chain would also get data
>> >> from the outside invokable that reads from the input iterator and
>> >> calls receiveElement() for the first operator in a chain.
>> >>
>> >> What do you think? I would of course be willing to implement this
>> myself.
>> >>
>> >> Cheers,
>> >> Aljoscha
>> >>
>>
Re: [DISCUSS] Change Streaming Operators to be Push-Only
Posted by Gyula Fóra <gy...@apache.org>.
I think this a good idea in general. I would try to minimize the methods we
include and make the ones that we keep very concrete. For instance i would
not have the receive barrier method as that is handled on a totally
different level already. And instead of punctuation I would directly add a
method to work on watermarks.
On Tuesday, May 5, 2015, Aljoscha Krettek <al...@apache.org> wrote:
> What do you mean by "losing iterations"?
>
> For the pros and cons:
>
> Cons: I can't think of any, since most of the operators are chainable
> already and already behave like a collector.
>
> Pros:
> - Unified model for operators, chainable operators don't have to
> worry about input iterators and the collect interface.
> - Enables features that we want in the future, such as barriers and
> punctuations because they don't work with the
> simple Collector interface.
> - The while-loop is moved outside of the operators, now the Task (the
> thing that runs Operators) can control the flow of data better and
> deal with
> stuff like barriers and punctuations. If we want to keep the
> main-loop inside each operator, then they all have to manage input
> readers and inline events manually.
>
> On Tue, May 5, 2015 at 2:41 PM, Kostas Tzoumas <ktzoumas@apache.org
> <javascript:;>> wrote:
> > Can you give us a rough idea of the pros and cons? Do we lose some
> > functionality by getting rid of iterations?
> >
> > Kostas
> >
> > On Tue, May 5, 2015 at 1:37 PM, Aljoscha Krettek <aljoscha@apache.org
> <javascript:;>>
> > wrote:
> >
> >> Hi Folks,
> >> while working on introducing source-assigned timestamps into streaming
> >> (https://issues.apache.org/jira/browse/FLINK-1967) I thought about how
> >> the punctuations (low watermarks) can be pushed through the system.
> >> The problem is, that operators can have two ways of getting input: 1.
> >> They read directly from input iterators, and 2. They act as a
> >> Collector and get elements via collect() from the previous operator in
> >> a chain.
> >>
> >> This makes it hard to push things through a chain that are not
> >> elements, such as barriers and/or punctuations.
> >>
> >> I propose to change all streaming operators to be push based, with a
> >> slightly improved interface: In addition to collect(), which I would
> >> call receiveElement() I would add receivePunctuation() and
> >> receiveBarrier(). The first operator in the chain would also get data
> >> from the outside invokable that reads from the input iterator and
> >> calls receiveElement() for the first operator in a chain.
> >>
> >> What do you think? I would of course be willing to implement this
> myself.
> >>
> >> Cheers,
> >> Aljoscha
> >>
>
Re: [DISCUSS] Change Streaming Operators to be Push-Only
Posted by Aljoscha Krettek <al...@apache.org>.
What do you mean by "losing iterations"?
For the pros and cons:
Cons: I can't think of any, since most of the operators are chainable
already and already behave like a collector.
Pros:
- Unified model for operators, chainable operators don't have to
worry about input iterators and the collect interface.
- Enables features that we want in the future, such as barriers and
punctuations because they don't work with the
simple Collector interface.
- The while-loop is moved outside of the operators, now the Task (the
thing that runs Operators) can control the flow of data better and
deal with
stuff like barriers and punctuations. If we want to keep the
main-loop inside each operator, then they all have to manage input
readers and inline events manually.
On Tue, May 5, 2015 at 2:41 PM, Kostas Tzoumas <kt...@apache.org> wrote:
> Can you give us a rough idea of the pros and cons? Do we lose some
> functionality by getting rid of iterations?
>
> Kostas
>
> On Tue, May 5, 2015 at 1:37 PM, Aljoscha Krettek <al...@apache.org>
> wrote:
>
>> Hi Folks,
>> while working on introducing source-assigned timestamps into streaming
>> (https://issues.apache.org/jira/browse/FLINK-1967) I thought about how
>> the punctuations (low watermarks) can be pushed through the system.
>> The problem is, that operators can have two ways of getting input: 1.
>> They read directly from input iterators, and 2. They act as a
>> Collector and get elements via collect() from the previous operator in
>> a chain.
>>
>> This makes it hard to push things through a chain that are not
>> elements, such as barriers and/or punctuations.
>>
>> I propose to change all streaming operators to be push based, with a
>> slightly improved interface: In addition to collect(), which I would
>> call receiveElement() I would add receivePunctuation() and
>> receiveBarrier(). The first operator in the chain would also get data
>> from the outside invokable that reads from the input iterator and
>> calls receiveElement() for the first operator in a chain.
>>
>> What do you think? I would of course be willing to implement this myself.
>>
>> Cheers,
>> Aljoscha
>>
Re: [DISCUSS] Change Streaming Operators to be Push-Only
Posted by Kostas Tzoumas <kt...@apache.org>.
Can you give us a rough idea of the pros and cons? Do we lose some
functionality by getting rid of iterations?
Kostas
On Tue, May 5, 2015 at 1:37 PM, Aljoscha Krettek <al...@apache.org>
wrote:
> Hi Folks,
> while working on introducing source-assigned timestamps into streaming
> (https://issues.apache.org/jira/browse/FLINK-1967) I thought about how
> the punctuations (low watermarks) can be pushed through the system.
> The problem is, that operators can have two ways of getting input: 1.
> They read directly from input iterators, and 2. They act as a
> Collector and get elements via collect() from the previous operator in
> a chain.
>
> This makes it hard to push things through a chain that are not
> elements, such as barriers and/or punctuations.
>
> I propose to change all streaming operators to be push based, with a
> slightly improved interface: In addition to collect(), which I would
> call receiveElement() I would add receivePunctuation() and
> receiveBarrier(). The first operator in the chain would also get data
> from the outside invokable that reads from the input iterator and
> calls receiveElement() for the first operator in a chain.
>
> What do you think? I would of course be willing to implement this myself.
>
> Cheers,
> Aljoscha
>