Hi everyone,
Thank you for all of your feedback and comments in google doc!
I have updated the google doc and add the UDFs part. For a short summary:
- Python TableAPI - Flink introduces a set of Python Table API Interfaces
which align with Flink Java Table API. It uses Py4j framework to
communicate between Python VM and Java VM.
- Python User-defined functions - IMO. Flink supports the communication
framework of UDFs, we will try to reuse the existing achievements of Beam
as much as possible, and do our best for this. The first step is
to solve the above interface definition problem, which turns `
WindowedValue<T>` into `T` in the FnDataService and BeamFnDataClient
interface definition, has been discussed in the Beam community.
The detail can be fonded here:
https://docs.google.com/document/d/1ybYt-0xWRMa1Yf5VsuqGRtOfJBz4p74ZmDxZYg3j_h8/edit?usp=sharing
So we can start the development of Table API without UDFs in Flink, and
work with the Beam community to promote the abstraction of Beam.
What do you think?
Regards,
Jincheng
jincheng sun <sunjincheng...@gmail.com> 于2019年4月17日周三 下午4:01写道：
> Hi Stephan,
>
> Thanks for your suggestion and summarize. :)
>
> ==> The FLIP should probably reflect the full goal rather than the
>> first implementation step only, this would make sure everyone understands
>> what the final goal of the effort is.
>
>
> I totally agree that we can implement the function in stages, but FLIP
> needs to reflect the full final goal. I agree with Thomas and you, I will
> add the design of the UDF part later.
>
> Yes, you are right, currently, we only consider the `flink run` and
> `python-shell` as the job entry point. and we should add REST API for
> another entry point.
>
> It would be super cool if the Python API would work seamlessly with all
>> modes of starting Flink jobs.
>
>
> If my understand you correctly, support Python TableAPI in Kubernetes, we
> only need to increase (or improve the existing) REST API corresponding to
> the Python Table API, of course, it also may need to release Docker Image
> that supports Python, it will easily deploy Python TableAPI into
> Kubernetes.
>
> So, Finally, we support the following ways to submit Python TableAPI:
> - Python Shell - interactive development.
> - CLI - submit the job by `flink run`. e.g: deploy job into the yarn
> cluster.
> - REST - submit the job by REST API. e.g: deploy job into the kubernetes
> cluster.
>
> Please correct me if there are any incorrect understanding.
>
> Thanks,
> Jincheng
>
>
> Stephan Ewen <se...@apache.org> 于2019年4月12日周五 上午12:22写道：
>
>> One more thought:
>>
>> The FLIP is very much centered on the CLI and it looks like it has mainly
>> batch jobs and session clusters in mind.
>>
>> In very many cases, especially in streaming cases, the CLI (or shell) is
>> not the entry point for a program.
>> See for example the use of Flink jobs on Kubernetes (Container Mode /
>> Entrypoint).
>>
>> It would be super cool if the Python API would work seamlessly with all
>> modes of starting Flink jobs.
>> That would make i available to all users.
>>
>> On Thu, Apr 11, 2019 at 5:34 PM Stephan Ewen <se...@apache.org> wrote:
>>
>> > Hi all!
>> >
>> > I think that all the opinions and ideas are not actually in conflict, so
>> > let me summarize what I understand is the proposal:
>> >
>> > *(1) Long-term goal: Full Python Table API with UDFs*
>> >
>> > To break the implementation effort up into stages, the first step
>> > would be the API without UDFs.
>> > Because of all the built-in functions in the Table API, this can
>> > already exist by itself, with some value, but ultimately is quite
>> limited
>> > without UDF support.
>> >
>> > ==> The FLIP should probably reflect the full goal rather than the
>> > first implementation step only, this would make sure everyone
>> understands
>> > what the final goal of the effort is.
>> >
>> >
>> > *(2) Relationship to Beam Language Portability*
>> >
>> > Flink's own Python Table API and Beam-Python on Flink add different
>> value
>> > and are both attractive for different scenarios.
>> >
>> > - Beam's Python API supports complex pipelines in a similar style as
>> the
>> > DataStream API. There is also the ecosystem of libraries built on top
>> that
>> > DSL, for example for machine learning.
>> >
>> > - Flink's Python Table API builds mostly relational expressions, plus
>> > some UDFs. Most of the Python code never executes in Python, though. It
>> is
>> > geared at use cases similar to Flink's Table API.
>> >
>> > Both approaches mainly differ in how the streaming DAG is built from
>> > Python code and received by the JVM.
>> >
>> > In previous discussions, we concluded that for inter process data
>> exchange
>> > (JVM <> Python), we want to share code with Beam.
>> > That part is possibly the most crucial piece to getting performance out
>> of
>> > the Python DSL, so will benefit from sharing development, optimizations,
>> > etc.
>> >
>> > Best,
>> > Stephan
>> >
>> >
>> >
>> >
>> > On Fri, Apr 5, 2019 at 5:25 PM jincheng sun <sunjincheng...@gmail.com>
>> > wrote:
>> >
>> >> One more thing It's better to mention that Flink table API is a
>> superset
>> >> of
>> >> Flink SQL, such as:
>> >> - AddColumns/DropColums/RenameColumns, the detail can be found in
>> Google
>> >> doc
>> >> <
>> >>
>> https://docs.google.com/document/d/1tryl6swt1K1pw7yvv5pdvFXSxfrBZ3_OkOObymis2ck/edit#heading=h.7rwcjbvr52dc
>> >> >
>> >> - Interactive Programming in Flink Table API, the detail can be found
>> in
>> >> FLIP-36
>> >> <
>> >>
>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-36%3A+Support+Interactive+Programming+in+Flink
>> >> >
>> >> I think In the future, more and more features that cannot be expressed
>> in
>> >> SQL will be added in Table API.
>> >>
>> >> Thomas Weise <thomas.we...@gmail.com> 于2019年4月5日周五 下午12:11写道：
>> >>
>> >> > Hi Jincheng,
>> >> >
>> >> > >
>> >> > > Yes, we can add use case examples in both google doc and FLIP， I
>> had
>> >> > > already add the simple usage in the google doc, here I want to know
>> >> which
>> >> > > kind of examples you want? :)
>> >> > >
>> >> >
>> >> > Do you have use cases where the Python table API can be applied
>> without
>> >> UDF
>> >> > support?
>> >> >
>> >> > (And where the same could not be accomplished with just SQL.)
>> >> >
>> >> >
>> >> > > The very short answer to UDF support is Yes. As you said, we need
>> UDF
>> >> > > support on the Python Table API, including (UDF, UDTF, UDAF). This
>> >> needs
>> >> > to
>> >> > > be discussed after basic Python TableAPI supported. Because UDF
>> >> involves
>> >> > > the management of the python environment, Runtime level Java and
>> >> Runtime
>> >> > > communication, and UDAF in Flink also involves the application of
>> >> State,
>> >> > so
>> >> > > this is a topic that is worth discussing in depth in a separate
>> >> thread.
>> >> > >
>> >> >
>> >> > The current proposal for job submission touches something that Beam
>> >> > portability already had to solve.
>> >> >
>> >> > If we think that the Python table API will only be useful with UDF
>> >> support
>> >> > (question above), then it may be better to discuss the first step
>> with
>> >> the
>> >> > final goal in mind. If we find that Beam can be used for the UDF part
>> >> then
>> >> > approach 1 vs. approach 2 in the doc (for the client side language
>> >> > boundary) may look different.
>> >> >
>> >> >
>> >> > >
>> >> > > I think that no matter how the Flink and Beam work together on the
>> UDF
>> >> > > level, it will not affect the current Python API (interface), we
>> can
>> >> > first
>> >> > > support the Python API in Flink. Then start the UDX (UDF/UDTF/UDAF)
>> >> > > support.
>> >> > >
>> >> > >
>> >> > I agree that the client side API should not be affected.
>> >> >
>> >> >
>> >> > > And great thanks for your valuable comments in Google doc! I will
>> >> > feedback
>> >> > > you in the google doc. :)
>> >> > >
>> >> > >
>> >> > > Regards,
>> >> > > Jincheng
>> >> > >
>> >> > > Thomas Weise <t...@apache.org> 于2019年4月4日周四 上午8:03写道：
>> >> > >
>> >> > > > Thanks for putting this proposal together.
>> >> > > >
>> >> > > > It would be nice, if you could share a few use case examples
>> (maybe
>> >> add
>> >> > > > them as section to the FLIP?).
>> >> > > >
>> >> > > > The reason I ask: The table API is immensely useful, but it isn't
>> >> clear
>> >> > > to
>> >> > > > me what value other language bindings provide without UDF
>> support.
>> >> With
>> >> > > > FLIP-38 it will be possible to write a program in Python, but not
>> >> > execute
>> >> > > > Python functions. Without UDF support, isn't it possible to
>> achieve
>> >> > > roughly
>> >> > > > the same with plain SQL? In which situation would I use the
>> Python
>> >> API?
>> >> > > >
>> >> > > > There was related discussion regarding UDF support in [1]. If the
>> >> > > > assumption is that such support will be added later, then I would
>> >> like
>> >> > to
>> >> > > > circle back to the question why this cannot be built on top of
>> >> Beam? It
>> >> > > > would be nice to clarify the bigger goal before embarking for the
>> >> first
>> >> > > > milestone.
>> >> > > >
>> >> > > > I'm going to comment on other things in the doc.
>> >> > > >
>> >> > > > [1]
>> >> > > >
>> >> > > >
>> >> > >
>> >> >
>> >>
>> https://lists.apache.org/thread.html/f6f8116b4b38b0b2d70ed45b990d6bb1bcb33611fde6fdf32ec0e840@%3Cdev.flink.apache.org%3E
>> >> > > >
>> >> > > > Thomas
>> >> > > >
>> >> > > >
>> >> > > > On Wed, Apr 3, 2019 at 12:35 PM Shuyi Chen <suez1...@gmail.com>
>> >> wrote:
>> >> > > >
>> >> > > > > Thanks a lot for driving the FLIP, jincheng. The approach looks
>> >> > > > > good. Adding multi-lang support sounds a promising direction to
>> >> > expand
>> >> > > > the
>> >> > > > > footprint of Flink. Do we have plan for adding Golang support?
>> As
>> >> > many
>> >> > > > > backend engineers nowadays are familiar with Go, but probably
>> not
>> >> > Java
>> >> > > as
>> >> > > > > much, adding Golang support would significantly reduce their
>> >> friction
>> >> > > to
>> >> > > > > use Flink. Also, do we have a design for multi-lang UDF
>> support,
>> >> and
>> >> > > > what's
>> >> > > > > timeline for adding DataStream API support? We would like to
>> help
>> >> and
>> >> > > > > contribute as well as we do have similar need internally at our
>> >> > > company.
>> >> > > > > Thanks a lot.
>> >> > > > >
>> >> > > > > Shuyi
>> >> > > > >
>> >> > > > > On Tue, Apr 2, 2019 at 1:03 AM jincheng sun <
>> >> > sunjincheng...@gmail.com>
>> >> > > > > wrote:
>> >> > > > >
>> >> > > > > > Hi All,
>> >> > > > > > As Xianda brought up in the previous email, There are a large
>> >> > number
>> >> > > of
>> >> > > > > > data analysis users who want flink to support Python. At the
>> >> Flink
>> >> > > API
>> >> > > > > > level, we have DataStreamAPI/DataSetAPI/TableAPI&SQL, the
>> Table
>> >> API
>> >> > > > will
>> >> > > > > > become the first-class citizen. Table API is declarative and
>> >> can be
>> >> > > > > > automatically optimized, which is mentioned in the Flink
>> >> mid-term
>> >> > > > roadmap
>> >> > > > > > by Stephan. So we first considering supporting Python at the
>> >> Table
>> >> > > > level
>> >> > > > > to
>> >> > > > > > cater to the current large number of analytics users. For
>> >> further
>> >> > > > promote
>> >> > > > > > Python support in flink table level. Dian, Wei and I
>> discussed
>> >> > > offline
>> >> > > > a
>> >> > > > > > bit and came up with an initial features outline as follows:
>> >> > > > > >
>> >> > > > > > - Python TableAPI Interface
>> >> > > > > > Introduce a set of Python Table API interfaces, including
>> >> > interface
>> >> > > > > > definitions such as Table, TableEnvironment, TableConfig,
>> etc.
>> >> > > > > >
>> >> > > > > > - Implementation Architecture
>> >> > > > > > We will offer two alternative architecture options, one for
>> >> pure
>> >> > > > Python
>> >> > > > > > language support and one for extended multi-language design.
>> >> > > > > >
>> >> > > > > > - Job Submission
>> >> > > > > > Provide a way that can submit(local/remote) Python Table
>> API
>> >> > jobs.
>> >> > > > > >
>> >> > > > > > - Python Shell
>> >> > > > > > Python Shell is to provide an interactive way for users to
>> >> write
>> >> > > and
>> >> > > > > > execute flink Python Table API jobs.
>> >> > > > > >
>> >> > > > > >
>> >> > > > > > The design document for FLIP-38 can be found here:
>> >> > > > > >
>> >> > > > > >
>> >> > > > > >
>> >> > > > >
>> >> > > >
>> >> > >
>> >> >
>> >>
>> https://docs.google.com/document/d/1ybYt-0xWRMa1Yf5VsuqGRtOfJBz4p74ZmDxZYg3j_h8/edit?usp=sharing
>> >> > > > > >
>> >> > > > > > I am looking forward to your comments and feedback.
>> >> > > > > >
>> >> > > > > > Best,
>> >> > > > > > Jincheng
>> >> > > > > >
>> >> > > > >
>> >> > > >
>> >> > >
>> >> >
>> >>
>> >
>>
>
