I’ve got an unconventional setup requiring me to use a Kafka testcontainer that needs to be available from several contexts:

• process/ app A; another testcontainer, obviously running from within docker, whose localhost is different from host’s
• process B; The ‘main’ process utilizing the testcontainers, localhost is the host’s

How I have this currently setup is by trying to use hostname that can be used to connect with both sides, and have process A set to connect to boostrap server using the hostname (creating the url myself), and B using the output from getBootstrapServers(). Process B has no issues connecting. Process A however can connect to the Kafka instance, but the addresses given from the bootstrap server points to localhost, which kills the connection.

Is there a way to get the kafka server to report the hostname I give it for Docker? I have tried withListener, but this causes instability/ breaks the kafka instance, preventing it from coming up at all. Any other recommendations to get this going? I’m imaginging if I use the hostname for both connections, then that should work but it’s a moot point if Kafka just reports back with localhost.

Setup of kafka:

RedpandaContainer kafka = new RedpandaContainer(DockerImageName.parse("docker.redpanda.com/redpandadata/redpanda:v23.1.2"))
                .withNetwork(Network.SHARED)
                .withAccessToHost(true)
                .withNetworkAliases(KAFKA_DEVSERVICE_HOSTNAME)
                .withListener(() -> KAFKA_DEVSERVICE_HOSTNAME + ":9092")
                ;

In another setup of Red Panda, I have the advertised listeners configured via the --advertise-kafka-addr command argument, but can’t find any documentation indicating environment variables that would do the same, and unsure I want to override the command for the testcontainer.