todo - run tests against docker desktop on linux

[alexanderankin]

from discussion in #610

[black-snow]

Let me know if I can assist you. Ain't got too much time to spare but I'll do my best ;)

[AlexElizard]

My little research.

Introductory:

1. Fedora Workstation 42 x86_64
2. Docker Desktop

Let's look at running a basic example from the official website

from testcontainers.postgres import PostgresContainer
import sqlalchemy

with PostgresContainer("postgres:16") as postgres:
    psql_url = postgres.get_connection_url()
    engine = sqlalchemy.create_engine(psql_url)
    with engine.begin() as connection:
        version, = connection.execute(sqlalchemy.text("SELECT version()")).fetchone()

print(version)

When DockerContainer is initialized, DockerClient is called, which gets the docker_host from tc.host in the ~/.testcontainers.properties file or from the DOCKER_HOST environment variable.

Because of this, attempting to start fails with the error docker.errors.DockerException: Error while fetching server API version: ('Connection aborted.', FileNotFoundError(2, 'No such file or directory')).

This problem can be solved in ~/.bashrc by setting the environment variable export DOCKER_HOST=unix://${HOME}/.docker/desktop/docker.sock or in ~/.testcontainers.properties by setting tc.host==unix://home/username/.docker/desktop/docker.sock. By the way, TESTCONTAINERS_DOCKER_SOCKET_OVERRIDE environment does not solve the problem.

Then we start to crash with the error docker.errors.APIError: 500 Server Error for http+docker://localhost/v1.51/containers/c57d89b2acb9f9fd4997576bdf62204daacbdfcf01006555cd0cda9e7f3624f7/start: Internal Server Error ("mounts denied: The path /socket_mnt/home/alexelizard/.docker/desktop/docker.sock is not shared from the host and is not known to Docker. You can configure shared paths from Docker -> Preferences... -> Resources -> File Sharing. See https://docs.docker.com/ for more info.")

This is an error on startup Ryuk. I couldn't figure out where Ryuk gets the /socket_mnt. Using export TESTCONTAINERS_DOCKER_SOCKET_OVERRIDE=${HOME}/.docker/desktop/docker.sock doesn't fix the issue with /socket_mnt.

The solution was found in testcontainers-java #7036 - you need to set the environment variable export TESTCONTAINERS_DOCKER_SOCKET_OVERRIDE=host.docker.internal.

In summary: to run testcontainers via Docker Desktop in Fedora Workstation, you need to set the following environment variables in ~/.bashrc:

export DOCKER_HOST=unix://${HOME}/.docker/desktop/docker.sock
export TESTCONTAINERS_DOCKER_SOCKET_OVERRIDE=host.docker.internal

Hope this helps.

[kiview]

Btw., it's totally ok to explicitly document, that Docker Desktop for Linux is not officially supported by tc-python (we have a similar situation for the other languages, also since having DD4L on CI is very hard).

[AlexElizard]

I'm not sure this is correct. Docker Desktop is quite widely used. Moreover, according to the documentation the Docker host should be detected automatically (item 6), but this doesn't happen.