CI configuration internals

Workflow rules

Pipelines for the GitLab project are created using the workflow:rules keyword feature of the GitLab CI/CD.

Pipelines are always created for the following scenarios:

• main branch, including on schedules, pushes, merges, and so on.
• Merge requests.
• Tags.
• Stable, auto-deploy, and security branches.

Pipeline creation is also affected by the following CI/CD variables:

• If $FORCE_GITLAB_CI is set, pipelines are created. Not recommended to use. See Avoid $FORCE_GITLAB_CI.
• If $GITLAB_INTERNAL is not set, pipelines are not created.

No pipeline is created in any other cases (for example, when pushing a branch with no MR for it).

The source of truth for these workflow rules is defined in .gitlab-ci.yml.

Avoid $FORCE_GITLAB_CI

The pipeline is very complex and we need to clearly understand the kind of pipeline we want to trigger. We need to know which jobs we should run and which ones we shouldn't.

If we use $FORCE_GITLAB_CI to force trigger a pipeline, we don't really know what kind of pipeline it is. The result can be that we don't run the jobs we want, or we run too many jobs we don't care about.

Some more context and background can be found at: Avoid blanket changes to avoid unexpected run

Here's a list of where we're using this right now, and should try to move away from using $FORCE_GITLAB_CI.

• JiHu validation pipeline
• Gitaly downstream GitLab pipeline

Default image

The default image is defined in .gitlab-ci.yml.

It includes Ruby, Go, Git, Git LFS, Chrome, Node, Yarn, PostgreSQL, and Graphics Magick.

The images used in our pipelines are configured in the gitlab-org/gitlab-build-images project, which is push-mirrored to gitlab/gitlab-build-images for redundancy.

The current version of the build images can be found in the "Used by GitLab section".

Default variables

In addition to the predefined CI/CD variables, each pipeline includes default variables defined in .gitlab-ci.yml.

Stages

The current stages are:

• sync: This stage is used to synchronize changes from gitlab-org/gitlab to gitlab-org/gitlab-foss.
• prepare: This stage includes jobs that prepare artifacts that are needed by jobs in subsequent stages.
• build-images: This stage includes jobs that prepare Docker images that are needed by jobs in subsequent stages or downstream pipelines.
• fixtures: This stage includes jobs that prepare fixtures needed by frontend tests.
• lint: This stage includes linting and static analysis jobs.
• test: This stage includes most of the tests, and DB/migration jobs.
• post-test: This stage includes jobs that build reports or gather data from the test stage's jobs (for example, coverage, Knapsack metadata, and so on).
• review: This stage includes jobs that build the CNG images, deploy them, and run end-to-end tests against Review Apps (see Review Apps for details). It also includes Docs Review App jobs.
• qa: This stage includes jobs that perform QA tasks against the Review App that is deployed in stage review.
• post-qa: This stage includes jobs that build reports or gather data from the qa stage's jobs (for example, Review App performance report).
• pages: This stage includes a job that deploys the various reports as GitLab Pages (for example, coverage-ruby, and webpack-report (found at https://gitlab-org.gitlab.io/gitlab/webpack-report/, but there is an issue with the deployment).
• notify: This stage includes jobs that notify various failures to Slack.

Dependency Proxy

Some of the jobs are using images from Docker Hub, where we also use ${GITLAB_DEPENDENCY_PROXY_ADDRESS} as a prefix to the image path, so that we pull images from our Dependency Proxy. By default, this variable is set from the value of ${GITLAB_DEPENDENCY_PROXY}.

${GITLAB_DEPENDENCY_PROXY} is a group CI/CD variable defined in gitlab-org as ${CI_DEPENDENCY_PROXY_GROUP_IMAGE_PREFIX}/. This means when we use an image defined as:

image: ${GITLAB_DEPENDENCY_PROXY_ADDRESS}alpine:edge

Projects in the gitlab-org group pull from the Dependency Proxy, while forks that reside on any other personal namespaces or groups fall back to Docker Hub unless ${GITLAB_DEPENDENCY_PROXY} is also defined there.

Work around for when a pipeline is started by a Project access token user

When a pipeline is started by a Project access token user (for example, the release-tools approver bot user which automatically updates the Gitaly version used in the main project), the Dependency proxy isn't accessible and the job fails at the Preparing the "docker+machine" executor step. To work around that, we have a special workflow rule, that overrides the ${GITLAB_DEPENDENCY_PROXY_ADDRESS} variable so that Dependency proxy isn't used in that case:

- if: '$CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH && $GITLAB_USER_LOGIN =~ /project_\d+_bot\d*/'
  variables:
    GITLAB_DEPENDENCY_PROXY_ADDRESS: ""

NOTE: We don't directly override the ${GITLAB_DEPENDENCY_PROXY} variable because group-level variables have higher precedence over .gitlab-ci.yml variables.

Common job definitions

Most of the jobs extend from a few CI definitions defined in .gitlab/ci/global.gitlab-ci.yml that are scoped to a single configuration keyword.

rules, if: conditions and changes: patterns

We're using the rules keyword extensively.

All rules definitions are defined in rules.gitlab-ci.yml, then included in individual jobs via extends.

The rules definitions are composed of if: conditions and changes: patterns, which are also defined in rules.gitlab-ci.yml and included in rules definitions via YAML anchors

if: conditions

changes: patterns

Best Practices

When to use extends:, <<: *xyz (YAML anchors), or !reference

Reference

Key takeaways

• If you need to extend a hash, you should use extends
• If you need to extend an array, you'll need to use !reference, or YAML anchors as last resort
• For more complex cases (for example, extend hash inside array, extend array inside hash, ...), you'll have to use !reference or YAML anchors

What can extends and YAML anchors do?

extends

• Deep merge for hashes
• NO merge for arrays. It overwrites (source)

YAML anchors

• NO deep merge for hashes, BUT it can be used to extend a hash (see the example below)
• NO merge for arrays, BUT it can be used to extend an array (see the example below)

A great example

This example shows how to extend complex YAML data structures with !reference and YAML anchors:

.strict-ee-only-rules:
  # `rules` is an array of hashes
  rules:
    - if: '$CI_PROJECT_NAME !~ /^gitlab(-ee)?$/ '
      when: never

# `if-security-merge-request` is a hash
.if-security-merge-request: &if-security-merge-request
  if: '$CI_PROJECT_NAMESPACE == "gitlab-org/security"'

# `code-qa-patterns` is an array
.code-qa-patterns: &code-qa-patterns
  - "{package.json,yarn.lock}"
  - ".browserslistrc"
  - "babel.config.js"
  - "jest.config.{base,integration,unit}.js"

.qa:rules:as-if-foss:
  rules:
    # We extend the `rules` array with an array of hashes directly
    - !reference [".strict-ee-only-rules", rules]
    # We extend a single array entry with a hash
    - <<: *if-security-merge-request
      # `changes` is an array, so we pass it an entire array
      changes: *code-qa-patterns

qa:selectors-as-if-foss:
  # We include the rules from .qa:rules:as-if-foss in this job
  extends:
    - .qa:rules:as-if-foss

Extend the .fast-no-clone-job job

Downloading the branch for the canonical project takes between 20 and 30 seconds.

Some jobs only need a limited number of files, which we can download via the GitLab API.

You can skip a job git clone/git fetch by adding the following pattern to a job.

Scenario 1: no before_script is defined in the job

This applies to the parent sections the job extends from as well.

You can just extend the .fast-no-clone-job:

Before:

  # Note: No `extends:` is present in the job
  a-job:
    script:
      - source scripts/rspec_helpers.sh scripts/slack
      - echo "No need for a git clone!"

After:

  # Note: No `extends:` is present in the job
  a-job:
    extends:
      - .fast-no-clone-job
    variables:
      FILES_TO_DOWNLOAD: >
        scripts/rspec_helpers.sh
        scripts/slack
    script:
      - source scripts/rspec_helpers.sh scripts/slack
      - echo "No need for a git clone!"

Scenario 2: a before_script block is already defined in the job (or in jobs it extends)

For this scenario, you have to:

1. Extend the .fast-no-clone-job as in the first scenario (this will merge the FILES_TO_DOWNLOAD variable with the other variables)
2. Make sure the before_script section from .fast-no-clone-job is referenced in the before_script we use for this job.

Before:

  .base-job:
    before_script:
      echo "Hello from .base-job"

  a-job:
    extends:
      - .base-job
    script:
      - source scripts/rspec_helpers.sh scripts/slack
      - echo "No need for a git clone!"

After:

  .base-job:
    before_script:
      echo "Hello from .base-job"

  a-job:
    extends:
      - .base-job
      - .fast-no-clone-job
    variables:
      FILES_TO_DOWNLOAD: >
        scripts/rspec_helpers.sh
        scripts/slack
    before_script:
      - !reference [".fast-no-clone-job", before_script]
      - !reference [".base-job", before_script]
    script:
      - source scripts/rspec_helpers.sh scripts/slack
      - echo "No need for a git clone!"

Caveats

• This pattern does not work if a script relies on git to access the repository, because we don't have the repository without cloning or fetching.
• The job using this pattern needs to have curl available.
• If you need to run bundle install in the job (even using BUNDLE_ONLY), you need to:
  • Download the gems that are stored in the gitlab-org/gitlab project.
    • You can use the download_local_gems shell command for that purpose.
  • Include the Gemfile, Gemfile.lock and Gemfile.checksum (if applicable)

Where is this pattern used?

• For now, we use this pattern for the following jobs, and those do not block private repositories:
  • review-build-cng-env for:
    • GITALY_SERVER_VERSION
    • GITLAB_ELASTICSEARCH_INDEXER_VERSION
    • GITLAB_KAS_VERSION
    • GITLAB_METRICS_EXPORTER_VERSION
    • GITLAB_PAGES_VERSION
    • GITLAB_SHELL_VERSION
    • scripts/trigger-build.rb
    • VERSION
  • review-deploy for:
    • GITALY_SERVER_VERSION
    • GITLAB_SHELL_VERSION
    • scripts/review_apps/review-apps.sh
    • scripts/review_apps/seed-dast-test-data.sh
    • VERSION
  • rspec:coverage for:
    • config/bundler_setup.rb
    • Gemfile
    • Gemfile.checksum
    • Gemfile.lock
    • scripts/merge-simplecov
    • spec/simplecov_env_core.rb
    • spec/simplecov_env.rb

Additionally, scripts/utils.sh is always downloaded from the API when this pattern is used (this file contains the code for .fast-no-clone-job).