README.md

Conduktor-only section

How to work on this fork️

🙂️ Before to start to work on this repo, be sure to read this paragraph, please 🙂️

We, at Conduktor, maintain a fork of the zio/zio-kafka repo so that we can release new versions as soon as we need them.

For that purpose and to adapt this repo to our needs, we created a new main branch, named zio2-main, which is configured to be our default branch.
This zio2-main is based on the master branch and MUST be rebased on it when the master branch is updated.

Our master branch represents and tracks the zio/zio-kafka master branch.
We MUST NOT push/merge anything specific to Conduktor in our master branch.
In order to keep this fork up-to-date with zio/zio-kafka, when the ZIO devs merge things in their master branch, we MUST rebase our master branch on their master branch and then, rebase our zio2-main branch on our master branch.

If you want to add some Conduktor-only things (CI stuff for example) to this fork, then you MUST start your new branch from our zio2-main branch.
If you want to add a feature to the official zio/zio-kafka repo, then you MUST start your new branch from our master branch.

Versioning scheme

For the ZIO2 versions of our fork of zio-kafka, here’s the versioning pattern to follow:

<condensed base zio-kafka version>-<our version of the lib>-cdk

in which:

• the <condensed base zio-kafka version> is, for example and for now, 201 because our fork is based on the version 2.0.1 of zio-kafka
• the <our version of the lib> is for now 1.0.0, as it’s our first version.

I hope this versioning will be flexible enough, so we can express anything we want and/or need and will allow us to easily track/stay up-to-date with the version of the upstream repo.

How to release a new version of this fork

The CI/CD pipeline of this fork has been adapted to follow the usual Conduktor CI/CD process.

To release a new version of this library, you just need to create a new release in this repo.
This will trigger a Github Actions pipeline that will publish the new version.

Please follow the versioning scheme described above.

ZIO Kafka

ZIO Kafka is a Kafka client for ZIO. It provides a purely functional, streams-based interface to the Kafka client and integrates effortlessly with ZIO and ZIO Streams.

Introduction

Apache Kafka is a distributed event streaming platform that acts as a distributed publish-subscribe messaging system. It enables us to build distributed streaming data pipelines and event-driven applications.

Kafka has a mature Java client for producing and consuming events, but it has a low-level API. ZIO Kafka is a ZIO native client for Apache Kafka. It has a high-level streaming API on top of the Java client. So we can produce and consume events using the declarative concurrency model of ZIO Streams.

Installation

In order to use this library, we need to add the following line in our build.sbt file:

libraryDependencies += "dev.zio" %% "zio-kafka" % "2.1.3" 

Example

Let's write a simple Kafka producer and consumer using ZIO Kafka with ZIO Streams. Before everything, we need a running instance of Kafka. We can do that by saving the following docker-compose script in the docker-compose.yml file and run docker-compose up:

version: '2'
services:
  zookeeper:
    image: confluentinc/cp-zookeeper:latest
    environment:
      ZOOKEEPER_CLIENT_PORT: 2181
      ZOOKEEPER_TICK_TIME: 2000
    ports:
      - 22181:2181
  
  kafka:
    image: confluentinc/cp-kafka:latest
    depends_on:
      - zookeeper
    ports:
      - 29092:29092
    environment:
      KAFKA_BROKER_ID: 1
      KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
      KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka:9092,PLAINTEXT_HOST://localhost:29092
      KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: PLAINTEXT:PLAINTEXT,PLAINTEXT_HOST:PLAINTEXT
      KAFKA_INTER_BROKER_LISTENER_NAME: PLAINTEXT
      KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1

Now, we can run our ZIO Kafka Streaming application:

import zio._
import zio.kafka.consumer._
import zio.kafka.producer.{Producer, ProducerSettings}
import zio.kafka.serde._
import zio.stream.ZStream

object MainApp extends ZIOAppDefault {
  val producer: ZStream[Producer, Throwable, Nothing] =
    ZStream
      .repeatZIO(Random.nextIntBetween(0, Int.MaxValue))
      .schedule(Schedule.fixed(2.seconds))
      .mapZIO { random =>
        Producer.produce[Any, Long, String](
          topic = "random",
          key = random % 4,
          value = random.toString,
          keySerializer = Serde.long,
          valueSerializer = Serde.string
        )
      }
      .drain

  val consumer: ZStream[Consumer, Throwable, Nothing] =
    Consumer
      .plainStream(Subscription.topics("random"), Serde.long, Serde.string)
      .tap(r => Console.printLine(r.value))
      .map(_.offset)
      .aggregateAsync(Consumer.offsetBatches)
      .mapZIO(_.commit)
      .drain

  def producerLayer =
    ZLayer.scoped(
      Producer.make(
        settings = ProducerSettings(List("localhost:29092"))
      )
    )

  def consumerLayer =
    ZLayer.scoped(
      Consumer.make(
        ConsumerSettings(List("localhost:29092")).withGroupId("group")
      )
    )

  override def run =
    producer.merge(consumer)
      .runDrain
      .provide(producerLayer, consumerLayer)
}

Resources

• An Introduction to ZIO Kafka
• Streaming microservices with ZIO and Kafka by Aleksandar Skrbic (February 2021)
• ZIO WORLD - ZIO Kafka by Aleksandar Skrbic (March 2020) — Aleksandar Skrbic presented ZIO Kafka, a critical library for the modern Scala developer, which hides some of the complexities of Kafka.

Documentation

Learn more on the ZIO Kafka homepage!

Contributing

For the general guidelines, see ZIO contributor's guide.

Code of Conduct

See the Code of Conduct

Support

Come chat with us on .

Credits

This library is heavily inspired and made possible by the research and implementation done in Alpakka Kafka, a library maintained by the Akka team and originally written as Reactive Kafka by SoftwareMill.

License

License

Copyright 2021 Itamar Ravid and the zio-kafka contributors. All rights reserved.