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Kafka, mail # user - Non-blocking Kafka stream iterators


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Re: Non-blocking Kafka stream iterators
Evan Chan 2013-01-22, 20:57
Hi Jay,

Actually, it's mostly the ability to easily cross-build;   also the ease of
understanding the code (less code to grok) and implementing alternatives (I
guess all of those falls under cleanliness).

thanks,
Evan
On Tue, Jan 22, 2013 at 12:47 PM, Jay Kreps <[EMAIL PROTECTED]> wrote:

> Hi Evan,
>
> Makes sense. Is your goal in separating the client shrinking the jar size?
> or just general cleanliness?
>
> -Jay
>
>
> On Tue, Jan 22, 2013 at 10:53 AM, Evan Chan <[EMAIL PROTECTED]> wrote:
>
> > Jay,
> >
> > Comments inlined.
> >
> > On Tue, Jan 22, 2013 at 10:15 AM, Jay Kreps <[EMAIL PROTECTED]> wrote:
> >
> > > Hey Evan,
> > >
> > > Great points, some comments:
> > > - Not sure if I understand what you mean by separating consumer and
> main
> > > logic.
> > >
> >
> > I just meant having a separate Scala/Java client jar, so it's more
> > lightweight and easier to build independently.... kind of like the
> > consumers for the other languages.
> >
> >
> > > - Yes, cross-building, I think this is in progress now for kafka as a
> > whole
> > > so it should be in either 0.8 or 0.8.1
> > > - Yes, forgot to mention offset initialization, but that is definitely
> > > needed.
> > >
> > > For the hasNext functionality, even that is not very good since if you
> > have
> > > two streams and want to take the next message from either you would
> have
> > to
> > > busy wait calling hasNext on both in a loop.
> > >
> > > An alternative would be something like
> > > val client = new ConsumerClient(topics, config)
> > > client.select(timeout: Long): Iterator[MessageAndMetadata]
> > >
> > > This method would have no internal threading. It would scatter-gather
> > over
> > > the topic/partitions assigned to this consumer (whether they are
> > statically
> > > or dynamically assigned would be specified in the config). The select
> > call
> > > would internally just do an epoll/select on all the connections and
> > return
> > > the first message set it gets back or an empty list if it hits the
> > timeout
> > > and no one has responded.
> > >
> >
> > Hm, I like that API actually.  It would definitely be more flexible.
> >
> >
> > >
> > > This api is less intuitive then the blocking iterator, but more
> flexible
> > > and enables a better, faster implementation. There would be no threads
> > > aside from the client's thread. It allows non-blocking or blocking
> > > consumption. And it generalizes easily to consuming from many
> > > topics/partitions simultaneously.
> > >
> > > We could implement an iterator like wrapper for this to ease the
> > transition
> > > that just used this api under the covers.
> > >
> > > Anyhow this is a ways out, and we haven't really had any proposals or
> > > discussions on it, but this is what I was thinking.
> > >
> > > -Jay
> > >
> > >
> > >
> > >
> > > On Tue, Jan 22, 2013 at 9:37 AM, Evan Chan <[EMAIL PROTECTED]> wrote:
> > >
> > > > Jay,
> > > >
> > > > For the consumer:
> > > > - Separation of the consumer logic from the main logic
> > > > - Making it easier to build the consumer for different versions of
> > Scala
> > > > (say 2.10)
> > > > - Make it easier to read from any offset you want, while being able
> to
> > > keep
> > > > partition management features
> > > > - Better support for Akka and other non-blocking / event-based
> > frameworks
> > > > (instead of a timeout, implement true hasNext functionality, for
> > example)
> > > >
> > > > thanks,
> > > > Evan
> > > >
> > > >
> > > > On Mon, Jan 21, 2013 at 9:27 AM, Jay Kreps <[EMAIL PROTECTED]>
> > wrote:
> > > >
> > > > > It's worth mentioning that we are interested in exploring potential
> > > > > generalizations of the producer and consumer API, but as a
> practical
> > > > matter
> > > > > most of the committers are working on getting a stable 0.8 release
> > out
> > > > the
> > > > > door. So an improved consumer and producer api would be a 0.9
> > feature.
> > > > >
> > > > > If you have a concrete thing you are trying to do now that is
> awkward

*Evan Chan*
Senior Software Engineer |
[EMAIL PROTECTED] | (650) 996-4600
www.ooyala.com | blog <http://www.ooyala.com/blog> |
@ooyala<http://www.twitter.com/ooyala>