[Bug]: Running on gitlab CI does not work as host.docker.internal is not available

[kicktipp]

Module

Core

Testcontainers version

1.17.2

Using the latest Testcontainers version?

Yes

Docker version

Docker version 20.10.17, build 100c701

What happened?

The docs for gitlab CI show a wrong config.toml. On linux the host.docker.internal is not reachable.

Test ist with

ping:
  stage: test
  script: apt update; apt install -y iputils-ping; ping -c1 host.docker.internal

The result is:

...
Setting up iputils-ping (3:20210202-1) ...
ping: host.docker.internal: Name or service not known
Cleaning up project directory and file based variables
ERROR: Job failed: exit code 1
...

I found some information about host.docker.internal on linux machines:
https://medium.com/@TimvanBaarsen/how-to-connect-to-the-docker-host-from-inside-a-docker-container-112b4c71bc66

I added extra_hosts=["host.docker.internal:host-gateway"] to my config.toml and no the server is reachable

The documentation should add this.

Relevant log output

Setting up iputils-ping (3:20210202-1) ...
ping: host.docker.internal: Name or service not known
Cleaning up project directory and file based variables
ERROR: Job failed: exit code 1

Additional Information

No response

[dkrtic]

From the docker documentation

We recommend that you connect to the special DNS name host.docker.internal which resolves to the internal IP address used by the host. This is for development purpose and does not work in a production environment outside of Docker Desktop.

I can't find which docker version is needed for host-gateway to work, this was added sometime last year .
It doesn't work on my Ubuntu 18.04 (Docker version 20.10.17) so I ended up using extra_hosts=["host.docker.internal:172.17.0.1"] in the runner's config.toml, where 172.17.0.1 is the IP address of the docker0 interface.

[eddumelendez]

host.docker.internal comes from Docker Desktop. GitLab CI is using docker-ce. Take a look at Testcontainers documentation about how to make this behavior work local and in ci.