If you’re using GitLab CI to build your software, you might also want to use it to build Docker images of your application.This can be a little tricky, because by default GitLab CI runs jobs inside Docker containers.

The standard technique for getting around this problem is using Docker-in-Docker, but you can also use a simpler technique by using Podman, the reimplemented version of Docker.Let’s see why and how.

Docs.gitlab.com › Ee › CiGitLab CI/CD Script Syntax | GitLab

Option #1: Docker-in-Docker

When you run the docker command-line tool, it is actually not doing much work itself.Instead, it talks to dockerd, a daemon or server typically running on the same machine where you’re running the CLI.The actual work of running a container or building an image is done by dockerd.

The.python:build job template provides an end-to-end distribution build configuration, effectively running the following command to build a project: python -m build -sdist -wheel. The outputs are uploaded as job artifacts. The following variables can be used to configure the build.

When you want to run docker inside GitLab CI, you face the issue that GitLab CI jobs typically run as Docker containers.So you can’t just rely on a normal dockerd being available as you would, for example, in a virtual machine.

• This script can be considered the main function of the extract, and is the file which gets run as the starting point of the extract DAG. When not to use Python Since this style guide is for the entire data team, it is important to remember that there is a time and place for using Python and it is usually outside of the data modeling phase.
• To run these tests automatically when you push code to your repository, add the following job to your.gitlab-ci.yml. Test:pytest: image: python:3.6 script: - pip install pytest -quiet - pytest. Pytest will automatically discover all test files in your project (all files named test.py or.test.py) and execute them.
• If you’re using GitLab CI to build your software, you might also want to use it to build Docker images of your application. This can be a little tricky, because by default GitLab CI runs jobs inside Docker containers. The standard technique for getting around this problem is using Docker-in-Docker, but you can also use a simpler technique by using Podman, the reimplemented version of Docker.

To help with this scenario, there’s a Docker image that runs dockerd for you: docker:dind.Once that is running, you can point docker at that running daemon and issue commands like docker build.

In the context of GitLab CI, your jobs can run services, which are also Docker containers.So we can configure .gitlab-ci.yml to run docker:dind as a service in a job:

In this case, the service is given the hostname alias dockerdaemon.You also need to tell the docker CLI how to find the server, which you can do via an environment variable DOCKER_HOST, as well as set a couple of other variables that make it work, and work faster:

A full configuration that builds an image and pushes it to the GitLab image registry corresponding to the GitLab CI repository looks like this:

For more details see the relevant GitLab CI documentation.

A working example

I’ve set up an example repository that contains this configuration.Here’s what the Dockerfile looks like:

Like most GitLab repositories, it has a corresponding Docker image registry, and you can run the image built by the above configuration like so:

Note: Outside the very specific topic under discussion, the Dockerfiles in this article are not examples of best practices, since the added complexity would obscure the main point of the article.

To ensure you’re following all the best practices you need to have a secure, correct, fast Dockerfiles, check out the Python on Docker Production Handbook.

Option #2: Podman

Podman is a reimplemented version of Docker from RedHat.It supports the same command-line options, but has a fundamentally different architecture: unlike Docker, there is no daemon by default.The CLI does all the work itself.

That means we can do a much simpler GitLab CI config, without the service running the daemon:

Notice all we had to do was change the docker command-line to do podman instead; they basically accept the same options.

A working example

The same example repository is also configured to use Podman.Again, you can run the resulting image:

Docker-in-Docker (DinD) vs Podman

.gitlab-ci.yml Run Python Script

Which of these two should you choose?DinD gives you access to BuildKit, which has some useful features and performance improvements; Podman does not support all of them yet, though it does support build secrets.

On the other hand, running the DinD daemon adds some overhead, since another image has to be downloaded; the DinD build adds another 20 seconds of fixed overhead in my test.For less trivial builds this overhead probably will be overwhelmed by other factors.

How Make A If Statement In The CI File

If you don’t care about BuildKit’s additional features, using Podman is just a little bit simpler while offering the same user experience.Finally, you could look into Buildah, which is how podman build is implemented: it’s a tool specifically focused only on building images.