Getting started with GitLab CI/CD

GitLab offers a continuous integration service. For each commit or push to trigger your CI pipeline, you must:

The .gitlab-ci.yml file tells the GitLab Runner what to do. A simple pipeline commonly has three stages:

  • build
  • test
  • deploy

You do not need to use all three stages; stages with no jobs are ignored.

The pipeline appears under the project’s CI/CD > Pipelines page. If everything runs OK (no non-zero return values), you get a green check mark associated with the commit. This makes it easy to see whether a commit caused any of the tests to fail before you even look at the job (test) log. Many projects use GitLab’s CI service to run the test suite, so developers get immediate feedback if they broke something.

It’s also common to use pipelines to automatically deploy tested code to staging and production environments.

If you’re already familiar with general CI/CD concepts, you can review which pipeline architectures can be used in your projects. If you’re coming over to GitLab from Jenkins, you can check out our reference for converting your pre-existing pipelines over to our format.

This guide assumes that you have:

  • A working GitLab instance of version 8.0+ or are using GitLab.com.
  • A project in GitLab that you would like to use CI for.
  • Maintainer or owner access to the project

Let’s break it down to pieces and work on solving the GitLab CI/CD puzzle.

Creating a .gitlab-ci.yml file

Before you create .gitlab-ci.yml let’s first explain in brief what this is all about.

What is .gitlab-ci.yml

The .gitlab-ci.yml file is where you configure what CI does with your project. It lives in the root of your repository.

On any push to your repository, GitLab will look for the .gitlab-ci.yml file and start jobs on Runners according to the contents of the file, for that commit.

Because .gitlab-ci.yml is in the repository and is version controlled, old versions still build successfully, forks can easily make use of CI, branches can have different pipelines and jobs, and you have a single source of truth for CI. You can read more about the reasons why we are using .gitlab-ci.yml in our blog about it.

Creating a simple .gitlab-ci.yml file

Note: A GitLab team member has made an unofficial visual pipeline editor. There is a plan to make it an official part of GitLab in the future, but it’s available for anyone who wants to try it at the above link.

You need to create a file named .gitlab-ci.yml in the root directory of your repository. This is a YAML file so you have to pay extra attention to indentation. Always use spaces, not tabs.

Below is an example for a Ruby on Rails project:

image: "ruby:2.5"

before_script:
  - apt-get update -qq && apt-get install -y -qq sqlite3 libsqlite3-dev nodejs
  - ruby -v
  - which ruby
  - gem install bundler --no-document
  - bundle install --jobs $(nproc)  "${FLAGS[@]}"

rspec:
  script:
    - bundle exec rspec

rubocop:
  script:
    - bundle exec rubocop

This is the simplest possible configuration that will work for most Ruby applications:

  1. Define two jobs rspec and rubocop (the names are arbitrary) with different commands to be executed.
  2. Before every job, the commands defined by before_script are executed.

The .gitlab-ci.yml file defines sets of jobs with constraints of how and when they should be run. The jobs are defined as top-level elements with a name (in our case rspec and rubocop) and always have to contain the script keyword. Jobs are used to create jobs, which are then picked by Runners and executed within the environment of the Runner.

What is important is that each job is run independently from each other.

If you want to check whether the .gitlab-ci.yml of your project is valid, there is a Lint tool under the page /-/ci/lint of your project namespace. You can also find a “CI Lint” button to go to this page under CI/CD ➔ Pipelines and Pipelines ➔ Jobs in your project.

For more information and a complete .gitlab-ci.yml syntax, please read the reference documentation on .gitlab-ci.yml.

Push .gitlab-ci.yml to GitLab

Once you’ve created .gitlab-ci.yml, you should add it to your Git repository and push it to GitLab.

git add .gitlab-ci.yml
git commit -m "Add .gitlab-ci.yml"
git push origin master

Now if you go to the Pipelines page you will see that the pipeline is pending.

Note: If you have a mirrored repository where GitLab pulls from, you may need to enable pipeline triggering in your project’s Settings > Repository > Pull from a remote repository > Trigger pipelines for mirror updates.

You can also go to the Commits page and notice the little pause icon next to the commit SHA.

New commit pending

Clicking on it you will be directed to the jobs page for that specific commit.

Single commit jobs page

Notice that there is a pending job which is named after what we wrote in .gitlab-ci.yml. “stuck” indicates that there is no Runner configured yet for this job.

The next step is to configure a Runner so that it picks the pending jobs.

Configuring a Runner

In GitLab, Runners run the jobs that you define in .gitlab-ci.yml. A Runner can be a virtual machine, a VPS, a bare-metal machine, a Docker container or even a cluster of containers. GitLab and the Runners communicate through an API, so the only requirement is that the Runner’s machine has network access to the GitLab server.

A Runner can be specific to a certain project or serve multiple projects in GitLab. If it serves all projects it’s called a Shared Runner.

Find more information about different Runners in the Runners documentation.

You can find whether any Runners are assigned to your project by going to Settings ➔ CI/CD. Setting up a Runner is easy and straightforward. The official Runner supported by GitLab is written in Go and its documentation can be found at https://docs.gitlab.com/runner/.

In order to have a functional Runner you need to follow two steps:

  1. Install it
  2. Configure it

Follow the links above to set up your own Runner or use a Shared Runner as described in the next section.

Once the Runner has been set up, you should see it on the Runners page of your project, following Settings ➔ CI/CD.

Activated runners

Shared Runners

If you use GitLab.com you can use the Shared Runners provided by GitLab Inc.

These are special virtual machines that run on GitLab’s infrastructure and can build any project.

To enable the Shared Runners you have to go to your project’s Settings ➔ CI/CD and click Enable shared runners.

Read more on Shared Runners.

Seeing the status of your pipeline and jobs

After configuring the Runner successfully, you should see the status of your last commit change from pending to either running, success or failed.

You can view all pipelines by going to the Pipelines page in your project.

Commit status

Or you can view all jobs, by going to the Pipelines ➔ Jobs page.

Commit status

By clicking on a job’s status, you will be able to see the log of that job. This is important to diagnose why a job failed or acted differently than you expected.

Build log

You are also able to view the status of any commit in the various pages in GitLab, such as Commits and Merge requests.

Examples

Visit the examples README to see a list of examples using GitLab CI with various languages.