fs2-kafka/Lobby

Kåre Blakstad

@kareblak

downstream, theres som impure stuff, but that shouldnt be any problem

the persistent store you're talking about could be compacted topics

which would make the whole model pretty nice

And also, N is never enough

becaause N is dependent on N-1 etc, so a snapshot of the actual accumulator, or at least the result from mapAccumulate is needed

Adam Chlupacek

@AdamChlupacek

yeah I guess. Anyhow you right that the compacted topics could be used for this.

Kåre Blakstad

@kareblak

I'm not using fs2-kafka atm, btw, so this would be a dirty impl on top of kafka-streams...

How do you guys usually store offsets with fs2-kafka? file system? db?

Adam Chlupacek

@AdamChlupacek

We do not. You have to manage them yourself. ie you could use the compacted topics for the offsets, that is actually how the native kafka client does it

Kåre Blakstad

@kareblak

Yeah, I know, but how do you usually do it?

I like the idea of handing this responsibility over to the user...

Adam Chlupacek

@AdamChlupacek

For some we use cassandra for some we use kafka. Depending on the needs

We should probably give an example how to use the persistent topics for it tho. So that people have easier time migrating.

Kåre Blakstad

@kareblak

Yeah, that would be nice, I guess

I love your Head/Tail offset apporach. It's just completely lacking in the kafka-clients

Adam Chlupacek

@AdamChlupacek

It all comes from allowing users to manage their own offsets. Plus few years of experience with using kafka in a large system :D

Kåre Blakstad

@kareblak

:thumbsup:

Andi Miller

@andimiller

have you considered adding the timestamp field in the producer?

KSQL gets a bit upset if I read data written by fs2-kafka

Adam Chlupacek

@AdamChlupacek

We are adhering to the kafka protocol, if you need some timestamps in the messages written to kafka, you can just add it there yourself. Or am I missing something? I dont want to add some additional data to everything just because of KSQL.

Andi Miller

@andimiller

there is part of the kafka protocol which has timestamps I believe

but it's optional

https://cwiki.apache.org/confluence/display/KAFKA/KIP-32+-+Add+timestamps+to+Kafka+message

Adam Chlupacek

@AdamChlupacek

Oooh, I see what you mean, we are just not populating the value, but it is in protocols. all that is required is to expose it via API as of now we jsut set it to None all the me, you can PR it if you want.

Andi Miller

@andimiller

I may do if I can make it work :)

Adam Chlupacek

@AdamChlupacek

Hmm actually this may required more thought to it, now that i am reading the link :/

Andi Miller

@andimiller

I think it's a case of adding a new codec in protocols

because it bumps the magic byte

Pavel Chlupacek

@pchlupacek

@andimiller any idea what version of kafka introduced this ?

Adam Chlupacek

@AdamChlupacek

In that case yeah, a whole new codec is required

Pavel Chlupacek

@pchlupacek

if you can please, could you open issue? We’ll look onto that

Andi Miller

@andimiller

in theory 0.10.2.0

Pavel Chlupacek

@pchlupacek

:-)

Andi Miller

@andimiller

will do, I'll try and gather some info

Pavel Chlupacek

@pchlupacek

excellent thanks a lot

Kåre Blakstad

@kareblak

Can you guys provide an example of fs2-kafka writing offsets back to kafka?

pacman899

@pacman899

HI, is there a way consuming one optional msg(latest) from a topic? maybe with timeout? it suppose to return Stream of one element of Option[Msg]

Pavel Chlupacek

@pchlupacek

@/all 0.4.0-M2 release agains fs2 1.0.0-M2 was published

Vinayak Pathak

@vinayakpathak

Hello. I'm trying to use version 0.2.0 and it looks like even getting kafka.client working requires a non-trivial amount of work. I seem to need the following implicits just to make it compile:

  implicit val _concurrent: Concurrent[IO] = IO.ioConcurrentEffect
  implicit val AG: AsynchronousChannelGroup = AsynchronousChannelGroup.withThreadPool(Executors.newFixedThreadPool(8))
  implicit val ec = ExecutionContext.fromExecutor(new ForkJoinPool(8))
  implicit val scheduler = Scheduler(corePoolSize = 8).compile.toList.unsafeRunSync().head
  implicit val logger = Logger.JDKLogger[IO](java.util.logging.Logger.getAnonymousLogger).unsafeRunSync()

I'm not really familiar with various concurrency and execution related functionalities in java and so I have no idea what I'm doing here. At the same time it seems to me that if these implicits were actually required it wouldve been mentioned on the readme? Am I doing something wrong?

Pavel Chlupacek

@pchlupacek

@vinayakpathak some of this is getting to be simplified with 0.4.0 release (also please do not use 0.2.x, but rather 0.4.x branch). However we prefer the configuration of concurrency to be explicit in most cases.

Vinayak Pathak

@vinayakpathak

I see. 0.4.x uses fs2 1.0.0, no? Is that considered stable yet?

Pavel Chlupacek

@pchlupacek

the last version of 1.0 has fixes that are not available in 0.10 and liekly won't be backported. The 1.0 still may have some API changes. We are using 1.0 in production atm.

Vinayak Pathak

@vinayakpathak

Okay I'll give it a shot then

Pavel Chlupacek

@pchlupacek

generally the 0.10 version of kafka was imho never used a lot. In our production code we were at 0.9 release for a long time, and now we went straight to 1.0

Vinayak Pathak

@vinayakpathak

you mean 0.10 version of fs2 right?

Pavel Chlupacek

@pchlupacek

yes

the 0.4.0 of fs2-kafka will get likely synced with latest fs2 next week,

so no you are i think on M3

1.0.0-M3

Vinayak Pathak

@vinayakpathak

fs2-kafka's readme says M4

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