Test container repository

The test container repository primarily relates to developing and maintaining test container code using Kafka image from the strimzi/test-container-images repository. The main dependency is the test container framework, which lets you control the lifecycle of the Docker container.

Why use a Test container?

Since the Docker image is a simple encapsulation of Kafka binaries, you can spin up a Kafka container rapidly. Therefore, it is a suitable candidate for the unit or integration testing. If you need something more complex, there is a multi-node Kafka cluster implementation with only infrastructure limitations. The most important classes are described here::

StrimziKafkaContainer is a single-node instance of Kafka using the image from quay.io/strimzi/kafka with the given version. You can use it in two ways:
1. As an embedded ZooKeeper to run inside a Kafka container.
2. As an external ZooKeeper. An additional configuration for Kafka brokers can be injected through the constructor. The first one is using an embedded ZooKeeper which will run inside Kafka container. Another option is to use @StrimziZookeeperContainer as an external ZooKeeper. An additional configuration for Kafka brokers can be injected through the constructor. This container is a good fit for integration testing, but for more comprehensive testing, we suggest using @StrimziKafkaCluster.
StrimziZookeeperContainer is an instance of ZooKeeper encapsulated inside a Docker container using an image from quay.io/strimzi/kafka with the given version. It can be combined with @StrimziKafkaContainer, but we suggest using directly @StrimziKafkaCluster for more complicated testing.
StrimziKafkaCluster is a multi-node instance of Kafka and ZooKeeper using the latest image from quay.io/strimzi/kafka with the given version. It's a perfect fit for integration or system testing. We always deploy one ZooKeeper with a specified number of Kafka instances, running as a separate container inside Docker. The additional configuration for Kafka brokers can be passed to the constructor.

In summary, you can use StrimziKafkaContainer to use a Kafka cluster with a single Kafka broker. Or you can use StrimziKafkaCluster for a Kafka cluster with multiple Kafka brokers.

How to use the Test container?

Using a given test container takes three simple steps:

Specify two environment variables
Add the Strimzi test container as a Maven dependency
Run Strimzi test container
1. default configuration
2. (optional) run Strimzi test container with additional configuration

First, you need to specify two essential environment variables:

STRIMZI_TEST_CONTAINER_KAFKA_VERSION - specification of the Kafka version to run with the given container. For example, 3.0.0.
STRIMZI_TEST_CONTAINER_IMAGE_VERSION - specification of the Strimzi test container image version that was built in the test-container-images repositories. For example, 0.1.0.

Add the Strimzi test container to the project as a Maven dependency:

// in case of 0.26.0 version
<dependency>
    <groupId>io.strimzi</groupId>
    <artifactId>strimzi-test-container</artifactId>
    <version>0.26.0</version>
</dependency>

Examples:

i) default configuration

final int brokerId = 1;

StrimziKafkaContainer strimziKafkaContainer = StrimziKafkaContainer.create(brokerId);
// startup of the Kafka container
strimziKafkaContainer.start();

ii) (Optional) Run Strimzi test container with additional configuration

final int brokerId = 1;

// additional configuration
Map<String, String> additionalKafkaConfiguration = Map.of(
    "log.cleaner.enable", "false", 
    "log.cleaner.backoff.ms", 
    "1000", "ssl.enabled.protocols", "TLSv1", 
    "log.index.interval.bytes", "2048"
);

StrimziKafkaContainer strimziKafkaContainer = StrimziKafkaContainer.createWithAdditionalConfiguration(brokerId, additionalKafkaConfiguration);
// startup of the Kafka container
strimziKafkaContainer.start();

Additional tips