# Dev Services for Kafka

If any Kafka-related extension is present (e.g. `quarkus-smallrye-reactive-messaging-kafka`), Dev Services for Kafka automatically starts a Kafka broker in dev mode and when running tests. So, you don’t have to start a broker manually. The application is configured automatically.

| Because starting a Kafka broker can be long, Dev Services for Kafka uses Redpanda, a Kafka compatible broker which starts in ~1 second.

## Enabling / Disabling Dev Services for Kafka

Dev Services for Kafka is automatically enabled unless:

- `quarkus.kafka.devservices.enabled` is set to `false`

- the `kafka.bootstrap.servers` is configured

- all the Reactive Messaging Kafka channels have the `bootstrap.servers` attribute set

Dev Services for Kafka relies on Docker to start the broker. If your environment does not support Docker, you will need to start the broker manually, or connect to an already running broker. You can configure the broker address using `kafka.bootstrap.servers`.

## Shared broker

Most of the time you need to share the broker between applications. Dev Services for Kafka implements a service discovery mechanism for your multiple Quarkus applications running in dev mode to share a single broker.

| Dev Services for Kafka starts the container with the `quarkus-dev-service-kafka` label which is used to identify the container.

If you need multiple (shared) brokers, you can configure the `quarkus.kafka.devservices.service-name` attribute and indicate the broker name. It looks for a container with the same value, or starts a new one if none can be found. The default service name is `kafka`.

Sharing is enabled by default in dev mode, but disabled in test mode. You can disable the sharing with `quarkus.kafka.devservices.shared=false`.

## Setting the port

By default, Dev Services for Kafka picks a random port and configures the application. You can set the port by configuring the `quarkus.kafka.devservices.port` property.

Note that the Kafka advertised address is automatically configured with the chosen port.

## Configuring the image

Dev Services for Kafka supports Redpanda, kafka-native and Strimzi (in Kraft mode) images.

Redpanda is a Kafka compatible event streaming platform. Because it provides a fast startup times, dev services defaults to Redpanda images from `vectorized/redpanda`. You can select any version from https://hub.docker.com/r/vectorized/redpanda.

kafka-native provides images of standard Apache Kafka distribution compiled to native binary using Quarkus and GraalVM. While still being experimental, it provides very fast startup times with small footprint.

Image type can be configured using

    quarkus.kafka.devservices.provider=kafka-native

Strimzi provides container images and Operators for running Apache Kafka on Kubernetes. While Strimzi is optimized for Kubernetes, the images work perfectly in classic container environments. Strimzi container images run "genuine" Kafka broker on JVM, which is slower to start.

    quarkus.kafka.devservices.provider=strimzi

For Strimzi, you can select any image with a Kafka version which has Kraft support (2.8.1 and higher) from https://quay.io/repository/strimzi-test-container/test-container?tab=tags

    quarkus.kafka.devservices.image-name=quay.io/strimzi-test-container/test-container:0.100.0-kafka-3.1.0

## Configuring Kafka topics

You can configure the Dev Services for Kafka to create topics once the broker is started. Topics are created with given number of partitions and 1 replica.

The following example creates a topic named `test` with 3 partitions, and a second topic named `messages` with 2 partitions.

    quarkus.kafka.devservices.topic-partitions.test=3
    quarkus.kafka.devservices.topic-partitions.messages=2

If a topic already exists with the given name, the creation is skipped, without trying to re-partition the existing topic to a different number of partitions.

You can configure timeout for Kafka admin client calls used in topic creation using `quarkus.kafka.devservices.topic-partitions-timeout`, it defaults to 2 seconds.

## Transactional and Idempotent producers support

By default, the Red Panda broker is configured to enable transactions and idempotence features. You can disable those using:

    quarkus.kafka.devservices.redpanda.transaction-enabled=false

| Redpanda transactions does not support exactly-once processing.