Hey Jungtaek,

Thanks for your interest, sometimes I also think such an API would be a
good thing.
I don't see any strong reasons neither in KIP-288 nor in KIP-266 why such
an API shouldn't be created, so go ahead with it, although you'll need to
create a short KIP for this as the KafkaConsumer class considered to be a
public API.

Best,
Viktor

On Wed, Aug 7, 2019 at 9:26 AM Jungtaek Lim <kabh...@gmail.com> wrote:

> If we just wanted to remove deprecation and let both co-exist, that would
> be also viable, though `poll(0)` is still a hack and it would be ideal to
> provide official approach to do so.
>
> On Wed, Aug 7, 2019 at 4:24 PM Jungtaek Lim <kabh...@gmail.com> wrote:
>
> > Hi devs,
> >
> > I'm trying to replace deprecated poll(long) with poll(Duration), and
> > realized there's no alternative which behaves exactly same as poll(0), as
> > poll(0) has been used as a hack to only update metadata instead of
> pulling
> > records. poll(Duration.ZERO) wouldn't behave same since even updating
> > metadata will be timed-out. So now end users would need to give more
> > timeout and even pull some records even they're only interested in
> metadata.
> >
> > I looked back some KIPs which brought the change, and "discarded" KIP
> > (KIP-288 [1]) actually proposed a new API which only pulls metadata.
> > KIP-266 [2] is picked up instead but it didn't cover all the things what
> > KIP-288 proposed. I'm seeing some doc explaining poll(0) hasn't been
> > supported officially, but the hack has been widely used and they can't be
> > ignored.
> >
> > Kafka test code itself relies on either deprecated poll(0),
> > or updateAssignmentMetadataIfNeeded, which seems to be private API only
> for
> > testing.
> > (Btw, I'd try out replacing poll(0) to updateAssignmentMetadataIfNeeded
> as
> > avoiding deprecated method - if it works I'll submit a PR.)
> >
> > I'm feeling that it would be ideal to expose
> > `updateAssignmentMetadataIfNeeded` to the public API, maybe with renaming
> > as `waitForAssignment` which was proposed in KIP-288 if it feels too
> long.
> >
> > What do you think? If it sounds feasible I'd like to try out contribution
> > on this. I'm new to contribute Kafka community, so not sure it would
> > require a new KIP or not.
> >
> > Thanks,
> > Jungtaek Lim (HeartSaVioR)
> >
> > 1.
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-288%3A+%5BDISCARDED%5D+Consumer.poll%28%29+timeout+semantic+change+and+new+waitForAssignment+method
> > 2.
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-266%3A+Fix+consumer+indefinite+blocking+behavior
> >
> >
>
> --
> Name : Jungtaek Lim
> Blog : http://medium.com/@heartsavior
> Twitter : http://twitter.com/heartsavior
> LinkedIn : http://www.linkedin.com/in/heartsavior
>

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