Configuring GitLab Runner with Docker for isolated build environments

Building Isolated Environments with Docker and GitLab Runner

To configure a GitLab Runner with Docker for isolated build environments using Pulumi, you will need to write a Pulumi program that sets up the necessary infrastructure. Firstly, the GitLab Runner is a build instance which is registered to your GitLab instance and runs the CI/CD jobs. Docker provides an excellent isolated environment for running these jobs so they don't interfere with each other or with the host system.

The following program outlines how to set up a GitLab Runner using Docker with Pulumi in TypeScript. To begin, you will use the gitlab.Runner resource, which allows you to register a new runner on your GitLab instance, and the docker.Container resource to create a Docker container in which the runner will execute the CI/CD jobs.

Before you start with your Pulumi program, ensure you have the necessary prerequisites:

Pulumi CLI installed.
Docker installed.
A GitLab account with sufficient permissions to add runners.
A registration token from your GitLab instance for the runner.

Now, let's dive into the code:

import * as pulumi from '@pulumi/pulumi';
import * as docker from '@pulumi/docker';
import * as gitlab from '@pulumi/gitlab';

// Replace these placeholder values with your actual GitLab registration information.
const gitlabToken = pulumi.secret('your-gitlab-registration-token'); // It's advised to keep secrets out of plain text!

// Create a Docker network for the GitLab Runner.
const runnerNetwork = new docker.Network('gitlab-runner-network', {
  name: 'gitlab-runner-network',
  driver: 'bridge',
});

// Define a Docker image for the GitLab Runner.
const runnerImage = new docker.RemoteImage('gitlab-runner-image', {
  name: 'gitlab/gitlab-runner:latest',
});

// Create a Docker container for the runner using the specified image.
const runnerContainer = new docker.Container('gitlab-runner-container', {
  image: runnerImage.latest,
  name: 'gitlab-runner',
  networksAdvanced: [{
    name: runnerNetwork.name,
  }],
  envs: [
    'CI_SERVER_URL=https://gitlab.com', // Replace with your GitLab instance URL if self-hosted.
    'REGISTRATION_TOKEN=' + gitlabToken, // Use the GitLab registration token.
    // Add other environment variables as required.
  ],
  // Configure the container's properties as needed.
});

// Register the GitLab Runner.
const registeredRunner = new gitlab.Runner('my-gitlab-runner', {
  description: 'Pulumi-managed GitLab Runner',
  active: true,
  locked: true,
  runUntagged: true,
  accessLevel: 'not_protected',
  maximumTimeout: 3600,
  registrationToken: gitlabToken,
  tagList: ['docker', 'pulumi'], // Specify relevant tags for your runner.
});

// Export the container's ID as a stack output.
export const runnerContainerId = runnerContainer.id;

This program will register a new GitLab Runner and create a corresponding Docker container for it to run in. The runner registration and its Docker container configuration are managed by Pulumi, which gives you infrastructure as code benefits such as versioning, auditing, and reusability.

A few points of emphasis in the code:

We create a private Docker network for the GitLab Runner to ensure it has network access to carry out CI jobs.
We then define a Docker image. In this case, we're using the gitlab/gitlab-runner image.
A new Docker container is created using the runner image. This container will be used to run the Git registry Runner. It's configured with the required environment variables, which will be used during the registration process with your GitLab instance.
Finally, we register the new GitLab Runner with the instance using the gitlab.Runner resource and pass in the necessary details, including the registration token from GitLab.

Make sure you have all the required tokens and URLs at hand, and be cautious with how you handle these secrets. It is crucial to store and manage sensitive information securely, which Pulumi allows you to do through its Secret management.

For more details on the resources used in this program, you can refer to the documentation for Docker and GitLab providers on Pulumi's website.