how can I create a Schema Registry test container and connect it to a Kafka test container?

[eladgazit]

[Mikhail]

All you need that is:

1. Create Kafka and Schema Registry containers in the same Network
2. Pass kafka bootstrap server to Schema Registry environment

I don't pretend to the perfect usage of testcontainers (so if anyone can review it and notice my mistakes that will be great). I prefer to create a generic (in case Schema Registry, Zookeeper and etc) container and pass it to the custom wrapper with necessary methods.
Thus, I create KafkaContainer

import org.testcontainers.containers.{KafkaContainer, Network}
import org.testcontainers.utility.DockerImageName

import scala.jdk.CollectionConverters._

class KafkaNodeContainer(container: KafkaContainer) {
  def getInternalHost: String = container.getEnvMap.asScala("KAFKA_HOST_NAME")

  def getBootstrap: String = container.getBootstrapServers

  def close(): Unit = container.close()
}

object KafkaNodeContainer {
  def make(network: Network, brokerId: Int = 1, withExternalZookeeper: Boolean = false): KafkaNodeContainer = {
    val hostName = s"kafka$brokerId"

    val container = new KafkaContainer(
      DockerImageName.parse("confluentinc/cp-kafka:6.1.1").asCompatibleSubstituteFor("confluentinc/cp-kafka")
    )
      .withNetwork(network)
      .withNetworkAliases(hostName)
      .withEnv(
        Map[String, String](
          "KAFKA_BROKER_ID" -> brokerId.toString,
          "KAFKA_HOST_NAME" -> hostName,
          "KAFKA_AUTO_CREATE_TOPICS_ENABLE" -> "false"
        ).asJava
      )
    if (withExternalZookeeper) container.withExternalZookeeper("zookeeper:2181")

    container.start()
    Thread.sleep(10000L)

    new KafkaNodeContainer(container)
  }
}

Note: Thread.sleep(10000L) need for initialization #134

then, SchemaRegistryContainer

import com.dimafeng.testcontainers.GenericContainer
import org.testcontainers.containers.Network

import scala.jdk.CollectionConverters._

class SchemaRegistryContainer(container: GenericContainer) {
  private val schemaPort = 8081

  def schemaUrl: SchemaUrl = SchemaUrl(s"http://${container.container.getHost}:${container.container.getMappedPort(schemaPort)}")

  def close(): Unit = container.container.close()
}

object SchemaRegistryContainer {
  def make(network: Network, kafkaHost: String): SchemaRegistryContainer = {
    val container = new GenericContainer(dockerImage = "confluentinc/cp-schema-registry:6.1.1")
    container.container.withNetwork(network)
    container.container.setEnv(List(
      s"SCHEMA_REGISTRY_HOST_NAME=${container.container.getHost}",
      s"SCHEMA_REGISTRY_KAFKASTORE_BOOTSTRAP_SERVERS=$kafkaHost:9092"
    ).asJava)

    container.start()
    Thread.sleep(3000L)

    new SchemaRegistryContainer(container)
  }
}

and, finally, combine containers inside test

val network: Network = Network.newNetwork()
val kfkNode: KafkaNodeContainer = KafkaNodeContainer.make(network)
val schNode: SchemaRegistryContainer = SchemaRegistryContainer.make(network, kfkNode.getInternalHost)

You could check the full example in repo

[Dmitry F]

@mikhailchuryakov thanks for sharing! Would you like to contribute this as a PR?

[Mikhail]

@dimafeng Yes, sure! But I need a little time.