flink-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Till Rohrmann <trohrm...@apache.org>
Subject Re: Machine Learning on Flink - Next steps
Date Fri, 10 Mar 2017 14:08:43 GMT
Thanks Theo for steering Flink's ML effort here :-)

I'd vote to concentrate on

- Online learning
- Low-latency prediction serving

because of the following reasons:

Online learning:

I agree that this topic is highly researchy and it's not even clear whether
it will ever be of any interest outside of academia. However, it was the
same for other things as well. Adoption in industry is usually slow and
sometimes one has to dare to explore something new.

Low-latency prediction serving:

Flink with its streaming engine seems to be the natural fit for such a task
and it is a rather low hanging fruit. Furthermore, I think that users would
directly benefit from such a feature.

Offline learning with Streaming API:

I'm not fully convinced yet that the streaming API is powerful enough
(mainly due to lack of proper iteration support and spilling capabilities)
to support a wide range of offline ML algorithms. And if then it will only
support rather small problem sizes because streaming cannot gracefully
spill the data to disk. There are still to many open issues with the
streaming API to be applicable for this use case imo.

Offline learning with the batch API:

For offline learning the batch API is imo still better suited than the
streaming API. I think it will only make sense to port the algorithms to
the streaming API once batch and streaming are properly unified. Alone the
highly efficient implementations for joining and sorting of data which can
go out of memory are important to support big sized ML problems. In
general, I think it might make sense to offer a basic set of ML primitives.
However, already offering this basic set is a considerable amount of work.

Concering the independent organization for the development: I think it
would be great if the development could still happen under the umbrella of
Flink's ML library because otherwise we might risk some kind of
fragmentation. In order for people to collaborate, one can also open PRs
against a branch of a forked repo.

I'm currently working on wrapping the project re-organization discussion
up. The general position was that it would be best to have an incremental
build and keep everything in the same repo. If this is not possible then we
want to look into creating a sub repository for the libraries (maybe other
components will follow later). I hope to make some progress on this front
in the next couple of days/week. I'll keep you updated.

As a general remark for the discussions on the google doc. I think it would
be great if we could at least mirror the discussions happening in the
google doc back on the mailing list or ideally conduct the discussions
directly on the mailing list. That's at least what the ASF encourages.


On Fri, Mar 10, 2017 at 10:52 AM, Gábor Hermann <mail@gaborhermann.com>

> Hey all,
> Sorry for the bit late response.
> I'd like to work on
> - Offline learning with Streaming API
> - Low-latency prediction serving
> I would drop the batch API ML because of past experience with lack of
> support, and online learning because the lack of use-cases.
> I completely agree with Kate that offline learning should be supported,
> but given Flink's resources I prefer using the streaming API as Roberto
> suggested. Also, full model lifecycle (or end-to-end ML) could be more
> easily supported in one system (one API). Connecting Flink Batch with Flink
> Streaming is currently cumbersome (although side inputs [1] might help). In
> my opinion, a crucial part of end-to-end ML is low-latency predictions.
> As another direction, we could integrate Flink Streaming API with other
> projects (such as Prediction IO). However, I believe it's better to first
> evaluate the capabilities and drawbacks of the streaming API with some
> prototype of using Flink Streaming for some ML task. Otherwise we could run
> into critical issues just as the System ML integration with e.g. caching.
> These issues makes the integration of Batch API with other ML projects
> practically infeasible.
> I've already been experimenting with offline learning with the Streaming
> API. Hopefully, I can share some initial performance results next week on
> matrix factorization. Naturally, I've run into issues. E.g. I could only
> mark the end of input with some hacks, because this is not needed at a
> streaming job consuming input forever. AFAIK, this would be resolved by
> side inputs [1].
> @Theodore:
> +1 for doing the prototype project(s) separately the main Flink
> repository. Although, I would strongly suggest to follow Flink development
> guidelines as closely as possible. As another note, there is already a
> GitHub organization for Flink related projects [2], but it seems like it
> has not been used much.
> [1] https://cwiki.apache.org/confluence/display/FLINK/FLIP-17+
> Side+Inputs+for+DataStream+API
> [2] https://github.com/project-flink
> On 2017-03-04 08:44, Roberto Bentivoglio wrote:
> Hi All,
>> I'd like to start working on:
>>   - Offline learning with Streaming API
>>   - Online learning
>> I think also that using a new organisation on github, as Theodore propsed,
>> to keep an initial indipendency to speed up the prototyping and
>> development
>> phases it's really interesting.
>> I totally agree with Katherin, we need offline learning, but my opinion is
>> that it will be more straightforward to fix the streaming issues than
>> batch
>> issues because we will have more support on that by the Flink community.
>> Thanks and have a nice weekend,
>> Roberto
>> On 3 March 2017 at 20:20, amir bahmanyari <amirtousa@yahoo.com.invalid>
>> wrote:
>> Great points to start:    - Online learning
>>>    - Offline learning with the streaming API
>>> Thanks + have a great weekend.
>>>        From: Katherin Eri <katherinmail@gmail.com>
>>>   To: dev@flink.apache.org
>>>   Sent: Friday, March 3, 2017 7:41 AM
>>>   Subject: Re: Machine Learning on Flink - Next steps
>>> Thank you, Theodore.
>>> Shortly speaking I vote for:
>>> 1) Online learning
>>> 2) Low-latency prediction serving -> Offline learning with the batch API
>>> In details:
>>> 1) If streaming is strong side of Flink lets use it, and try to support
>>> some online learning or light weight inmemory learning algorithms. Try to
>>> build pipeline for them.
>>> 2) I think that Flink should be part of production ecosystem, and if now
>>> productions require ML support, multiple models deployment and so on, we
>>> should serve this. But in my opinion we shouldn’t compete with such
>>> projects like PredictionIO, but serve them, to be an execution core. But
>>> that means a lot:
>>> a. Offline training should be supported, because typically most of ML
>>> algs
>>> are for offline training.
>>> b. Model lifecycle should be supported:
>>> ETL+transformation+training+scoring+exploitation quality monitoring
>>> I understand that batch world is full of competitors, but for me that
>>> doesn’t mean that batch should be ignored. I think that separated
>>> streaming/batching applications causes additional deployment and
>>> exploitation overhead which typically tried to be avoided. That means
>>> that
>>> we should attract community to this problem in my opinion.
>>> пт, 3 мар. 2017 г. в 15:34, Theodore Vasiloudis <
>>> theodoros.vasiloudis@gmail.com>:
>>> Hello all,
>>>  From our previous discussion started by Stavros, we decided to start a
>>> planning document [1]
>>> to figure out possible next steps for ML on Flink.
>>> Our concerns where mainly ensuring active development while satisfying
>>> the
>>> needs of
>>> the community.
>>> We have listed a number of proposals for future work in the document. In
>>> short they are:
>>>    - Offline learning with the batch API
>>>    - Online learning
>>>    - Offline learning with the streaming API
>>>    - Low-latency prediction serving
>>> I saw there is a number of people willing to work on ML for Flink, but
>>> the
>>> truth is that we cannot
>>> cover all of these suggestions without fragmenting the development too
>>> much.
>>> So my recommendation is to pick out 2 of these options, create design
>>> documents and build prototypes for each library.
>>> We can then assess their viability and together with the community decide
>>> if we should try
>>> to include one (or both) of them in the main Flink distribution.
>>> So I invite people to express their opinion about which task they would
>>> be
>>> willing to contribute
>>> and hopefully we can settle on two of these options.
>>> Once that is done we can decide how we do the actual work. Since this is
>>> highly experimental
>>> I would suggest we work on repositories where we have complete control.
>>> For that purpose I have created an organization [2] on Github which we
>>> can
>>> use to create repositories and teams that work on them in an organized
>>> manner.
>>> Once enough work has accumulated we can start discussing contributing the
>>> code
>>> to the main distribution.
>>> Regards,
>>> Theodore
>>> [1]
>>> https://docs.google.com/document/d/1afQbvZBTV15qF3vobVWUjxQc49h3U
>>> d06MIRhahtJ6dw/
>>> [2] https://github.com/flinkml
>>> --
>>> *Yours faithfully, *
>>> *Kate Eri.*

  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message