Bug: kafka - doesn't work when using different DOCKER_HOST unless ADV_HOST is overloaded

[karelbilek]

Describe the bug
If you are using different DOCKER_HOST than localhost, kafka gnomock doesn't work.

To Reproduce

• have docker on a different host than localhost (for example, with DIND in gitlab CI)
• set DOCKER_HOST correctly
• run the default kafka test https://github.com/orlangure/gnomock/blob/master/preset/kafka/preset_test.go
• it fails on failure to connect to 127.0.0.1

Expected behavior
Everything works

System (please complete the following information):

• Gitlab CI, in my case

Additional context
The whole issue is caused by ADV_HOST being hard-coded to 127.0.0.1 in the preset.

The solution was, for me, write this at the start of the test:

	dockerIP := ""
	if dh := os.Getenv("DOCKER_HOST"); dh != "" {
		u, err := url.Parse(dh)
		if err == nil {
			if host := u.Hostname(); host != "" {
				ips, err := net.LookupIP(host)
				if err != nil {
					t.Fatalf("Could not get IPs: %v\n", err)
				}
				dockerIP = ips[0].String()
			}
		}
	}

And later:

	opts := []gnomock.Option{
		gnomock.WithDebugMode(), gnomock.WithLogWriter(os.Stdout),
		gnomock.WithContainerName("kafka"),
	}
	if dockerIP != "" {
		opts = append(opts, gnomock.WithEnv("ADV_HOST="+dockerIP))
	}
	container, err := gnomock.Start(
		p,
		opts...,
	)

This should be either set automatically (I am not sure why is the localhost IP hardcoded, as gnomock does know that I am using DOCKER_HOST) or, at least, documented

[karelbilek]

The hardcoded localhost is here

gnomock/preset/kafka/preset.go

Line 102 in 6bb416a

gnomock.WithEnv("ADV_HOST=127.0.0.1"),

[karelbilek]

Note, you cannot use the DOCKER_HOST directly, you need to first resolve it if it's not an IP address, otherwise I get error replication-factor is invalid (not sure what that means)

[orlangure]

Thanks for reporting this @karelbilek.
Do you think the code you suggested can be merged into the Kafka preset, instead of being used externally in the test?

[Ocramius]

Heyo, I just ran into this same issue as well.

The problem is that DOCKER_HOST is obviously not 127.0.0.1 for me, and in my case, I'm running the command from a docker-compose environment where networks: are defined too, further restricting interactions.

My setup roughly:

services:
  - docker:latest-dind # no, I don't actually use `latest` :-P 

integration-test:
  script:
    - docker compose run --rm my-service ./run-tests.sh

My docker-compose.yml is roughly:

services:
  my-service:
    image: some-image
    networks:
      - my-network

networks:
  my-network:
    driver: bridge

In this setup, I'm having a hard time figuring how the docker:dind DOCKER_HOST should be passed down to docker-compose.yml and further down to my-service.

In fact, assuming I can resolve DOCKER_HOST to an IP upfront: isn't that IP inaccessible from within my-service, given the different networks?

EDIT: closely related: https://github.com/testcontainers/testcontainers-go/blob/f09b3af2cb985a17bd2b2eaaa5d384882ded8e28/docs/system_requirements/ci/gitlab_ci.md