flink-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Gyula Fóra <gyula.f...@gmail.com>
Subject Re: [DISCUSS] FLIP-22: Eager State Declaration
Date Fri, 07 Jul 2017 12:21:47 GMT
Hi all,

Thanks for the proposal I definitely see the value in making eager
registration as a requirement for several features that you mentioned
(mostly related to state serialization/format etc.).

The only problem I see which has been mentioned by others is that the lack
of lazy (dynamic) state registration might be a blocker for some complex
application logic. In these cases users would have to register more generic
state types at initialization than otherwise necessary making the programs
less efficient.

Maybe it would still make sense to support lazy state registration but not
allow migration of these states in the future? On the other hand I dont
feel very strongly about this as the eager registration should cover most
use-cases with workarounds for the more complex cases.

Gyula

SHI Xiaogang <shixiaogangg@gmail.com> ezt írta (időpont: 2017. júl. 5.,
Sze, 4:36):

> Hi Tzu-Li,
>
> Thanks for the proposal. The changes are great. I have several questions
> about some details.
>
> First, do you have any plan to provide a method to remove states? Now
> states can only be created (either lazily or eagerly), but cannot be
> removed. We cannot remove those states not registered because they may be
> accessed later (with those deprecated methods).
>
> Second, what about exposing namespaces to users? Now namespaces are only
> used in window streams and all user states are in the void namespace. But
> some users may come across similar scenarios to window streams where states
> are closely related to arrived records and cannot be known beforehand.
> Since namespaces are not exposed, they have to create new states when new
> records arrive. MapState is another choice, but will be less efficient in
> some cases. If we can expose namespaces to users, these users may benefit
> from eagerly declared states. I think the change will not break existing
> interfaces.
>
> Looking forwards to your comments.
>
> Regards,
> Xiaogang
>
>
>
>
>
> 2017-07-05 3:53 GMT+08:00 Chesnay Schepler <chesnay@apache.org>:
>
> > Could you add an example to the FLIP for how a user can register a state
> > with the methods in the RichFunction interface?
> > Currently it only contains an example for the annotation option.
> >
> > These methods look like they are called by the user, but that doesn't
> > really make sense to me as after all the user has to
> > implement them.
> >
> > To me a more intuitive signature would be
> >
> > |void registerKeyedState(StateDescriptorRegistry registry);|
> >
> > that is called by the system when a UDF is provided by a user who then
> > registers all the state descriptors he has.
> >
> >
> > On 04.07.2017 20:00, Tzu-Li (Gordon) Tai wrote:
> >
> >> Hi Flink devs!
> >>
> >> I would like to propose the following FLIP - Eager State Declaration for
> >> Flink managed state: https://cwiki.apache.org/confl
> >> uence/display/FLINK/FLIP-22%3A+Eager+State+Declaration.
> >> The proposal is a result of some offline discussions with Aljoscha
> >> Krettek, Stephan Ewen, and Stefan Richter.
> >>
> >> With how the current managed state declaration interfaces work, users
> may
> >> declare state lazily while jobs are running.
> >> This behavior is a direct blocker for several state management features
> >> we wish to make a reality in the future.
> >> I also see it as an opportunity to make the interfaces for keyed /
> >> operator managed state declarations more unified at the API level, as
> well
> >> as improved user experience for general use cases.
> >>
> >> The most important part of the required changes is the deprecation of
> >> existing APIs and introducing new state declaration interfaces.
> >> Since this would be a rework of the state interfaces, it would be great
> >> to hear thoughts on this and make sure that the proposal is what we
> want in
> >> the long run!
> >>
> >> Happy to hear feedback on this :)
> >>
> >> Cheers,
> >> Gordon
> >>
> >
> >
> >
>

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