CI/CD components

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Components repository

A components repository is a GitLab project with a repository that hosts one or more pipeline components. A pipeline component is a reusable single pipeline configuration unit. Use them to compose an entire pipeline configuration or a small part of a larger pipeline.

A component can optionally take input parameters.

Create a components repository

To create a components repository, you must:

  1. Create a new project with a README.md file.

  2. Create a template.yml file inside the project’s root directory that contains the configuration you want to provide as a component. For example:

    spec:
  inputs:
    stage:
      default: test
---
component-job:
  script: echo job 1
  stage: $[[ inputs.stage ]]

Directory structure

A components repository can host one or more components, and must follow a mandatory file structure.

Component configurations can be saved through the following directory structure, containing:

  • A templates directory at the top level of your components repository. All component configuration files should be saved under this directory.
  • Files ending in .yml containing the component configurations, one file per component.
  • A Markdown README.md file explaining the details of all the components in the repository.

For example, if the project contains a single component and a pipeline to test the component, the file structure should be similar to:

├── templates/
│   └── only_template.yml
├── README.md
└── .gitlab-ci.yml

This example component could be referenced with a path similar to gitlab.com/my-username/my-component/only_template@<version>, if the project is:

  • On GitLab.com
  • Named my-component
  • In a personal namespace named my-username

The templates directory and the suffix of the configuration file should be excluded from the referenced path.

If the project contains multiple components, then the file structure should be similar to:

├── README.md
├── .gitlab-ci.yml
└── templates/
    └── all-scans.yml
    └── secret-detection.yml

These components would be referenced with these paths:

  • gitlab.com/my-username/my-component/all-scans
  • gitlab.com/my-username/my-component/secret-detection

You can omit the filename in the path if the configuration file is named template.yml. For example, the following component could be referenced with gitlab.com/my-username/my-component/dast:

├── README.md
├── .gitlab-ci.yml
├── templates/
│   └── dast
│       └── template.yml

Component configurations saved in any directory (deprecated)

note
Saving component configurations through this directory structure is deprecated.

Components configurations can be saved through the following directory structure, containing:

  • template.yml: The component configuration, one file per component. If there is only one component, this file can be in the root of the project. If there are multiple components, each file must be in a separate subdirectory.
  • README.md: A documentation file explaining the details of all the components in the repository.

For example, if the project is on GitLab.com, named my-component, and in a personal namespace named my-username:

  • Containing a single component and a simple pipeline to test the component, then the file structure might be:

    ├── template.yml
├── README.md
└── .gitlab-ci.yml

    The .gitlab-ci.yml file is not required for a CI/CD component to work, but testing the component in a pipeline in the project is recommended.

    This component is referenced with the path gitlab.com/my-username/my-component@<version>.

  • Containing one default component and multiple sub-components, then the file structure might be:

    ├── template.yml
├── README.md
├── .gitlab-ci.yml
├── unit/
│   └── template.yml
└── integration/
    └── template.yml

    These components are identified by these paths:

    • gitlab.com/my-username/my-component
    • gitlab.com/my-username/my-component/unit
    • gitlab.com/my-username/my-component/integration

It is possible to have a components repository with no default component, by having no template.yml in the root directory.

Additional notes:

Nesting of components is not possible. For example:

├── unit/
│   └── template.yml
│   └── another_folder/
│       └── nested_template.yml

Release a component

To create a release for a CI/CD component, use either:

All released versions of the components are displayed in the CI/CD Catalog page for the given resource, providing users with information about official releases.

Components can be used without being released, but only with a commit SHA or a branch name. To enable the use of tags or the ~latest version keyword, you must create a release.

Use a component in a CI/CD configuration

You can add a component to a CI/CD configuration with the include: component keyword. For example:

include:
  - component: gitlab.example.com/my-namespace/my-component@1.0
    inputs:
      stage: build

The component is identified by a unique address in the form <fully-qualified-domain-name>/<component-path>@<specific-version>, where:

  • <fully-qualified-domain-name> matches the GitLab host. You can only reference components in the same GitLab instance as your project.
  • <component-path> is the component project’s full path and directory where the component YAML file is located.
  • <specific-version> is the version of the component. In order of highest priority first, the version can be:
    • A branch name, for example main.
    • A commit SHA, for example e3262fdd0914fa823210cdb79a8c421e2cef79d8.
    • A tag, for example: 1.0. If a tag and branch exist with the same name, the tag takes precedence over the branch. If a tag and commit SHA exist with the same name, the commit SHA takes precedence over the tag.
    • ~latest, which is a special version that always points to the most recent released tag. Available only if the component has been released.

For example, for a component repository located at gitlab-org/dast on gitlab.com, the path:

  • gitlab.com/gitlab-org/dast@main targets the template.yml in the root directory on the main branch.
  • gitlab.com/gitlab-org/dast@e3262fdd0914fa823210cdb79a8c421e2cef79d8 targets the same file for the specified commit SHA.
  • gitlab.com/gitlab-org/dast@1.0 targets the same file for the 1.0 tag.
  • gitlab.com/gitlab-org/dast@~latest targets the same file for the latest release.
  • gitlab.com/gitlab-org/dast/api-scan@main targets a different file, the template.yml in the /api-scan directory in the component repository, for the main branch.

Best practices

Avoid using global keywords

Avoid using global keywords in a component. Using these keywords in a component affects all jobs in a pipeline, including jobs directly defined in the main .gitlab-ci.yml or in other included components.

As an alternative to global keywords, instead:

  • Add the configuration directly to each job, even if it creates some duplication in the component configuration.
  • Use the extends keyword in the component.

For example, using the default keyword is not recommended:

# Not recommended
default:
  image: ruby:3.0

rspec-1:
  script: bundle exec rspec dir1/

rspec-2:
  script: bundle exec rspec dir2/

Instead, you can:

  • Add the configuration to each job:

    rspec-1:
  image: ruby:3.0
  script: bundle exec rspec dir1/

rspec-2:
  image: ruby:3.0
  script: bundle exec rspec dir2/

  • Use extends to reuse configuration:

    .rspec-image:
  image: ruby:3.0

rspec-1:
  extends:
    - .rspec-image
  script: bundle exec rspec dir1/

rspec-2:
  extends:
    - .rspec-image
  script: bundle exec rspec dir2/

Replace hard-coded values with inputs

Avoid hard-coding values in CI/CD components. Hard-coded values might force component users to need to review the component’s internal details and adapt their pipeline to work with the component.

A common keyword with problematic hard-coded values is stage. If a component job’s stage is set to a specific value, the pipeline using the component must define the exact same stage. Additionally, if the component user wants to use a different stage, they must override the configuration.

The preferred method is to use the input keyword. The component user can specify the exact value they need.

For example:

  • In the component configuration:

    spec:
  inputs:
    stage:
      default: test
---
unit-test:
  stage: $[[ inputs.stage ]]
  script: echo unit tests

integration-test:
  stage: $[[ inputs.stage ]]
  script: echo integration tests

  • In the project using the component:

    include:
  - component: gitlab.com/gitlab-org/ruby-test@1.0
    inputs:
      stage: verify

stages: [verify, deploy]

Replace custom CI/CD variables with inputs

When using CI/CD variables in a component, evaluate if the inputs keyword should be used instead. Avoid requiring a user to define custom variables to change a component’s behavior. You should try to use inputs for any component customization.

Inputs are explicitly defined in the component’s specs, and are better validated than variables. For example, if a required input is not passed to the component, GitLab returns a pipeline error. By contrast, if a variable is not defined, its value is empty, and there is no error.

For example, use inputs instead of variables to let users change a scanner’s output format:

  • In the component configuration:

    spec:
  inputs:
    scanner-output:
      default: json
---
my-scanner:
  script: my-scan --output $[[ inputs.scanner-output ]]

  • In the project using the component:

    include:
  - component: gitlab.example.com/my-scanner@1.0
    inputs:
      scanner-output: yaml

In other cases, CI/CD variables are still preferred, including:

Use semantic versioning

When tagging and releasing new versions of components, you should use semantic versioning. Semantic versioning is the standard for communicating that a change is a major, minor, patch, or other kind of change.

You should use at least the major.minor format, as this is widely understood. For example, 2.0 or 2.1.

Other examples of semantic versioning:

  • 1.0.0
  • 2.1.3
  • 1.0.0-alpha
  • 3.0.0-rc1

Test the component

Testing CI/CD components as part of the development workflow is strongly recommended and helps ensure consistent behavior.

Test changes in a CI/CD pipeline (like any other project) by creating a .gitlab-ci.yml in the root directory.

For example:

include:
  # include the component located in the current project from the current SHA
  - component: gitlab.com/$CI_PROJECT_PATH@$CI_COMMIT_SHA
    inputs:
      stage: build

stages: [build, test, release]

# Expect `component-job` is added.
# This example tests that the included component works as expected.
# You can inspect data generated by the component, use GitLab API endpoints or third-party tools.
ensure-job-added:
  stage: test
  image: badouralix/curl-jq
  script:
    - |
      route="https://gitlab.com/api/v4/projects/$CI_PROJECT_ID/pipelines/$CI_PIPELINE_ID/jobs"
      count=`curl --silent --header "PRIVATE-TOKEN: $API_TOKEN" $route | jq 'map(select(.name | contains("component-job"))) | length'`
      if [ "$count" != "1" ]; then
        exit 1
      fi

# If we are tagging a release with a specific convention ("v" + number) and all
# previous checks succeeded, we proceed with creating a release automatically.
create-release:
  stage: release
  image: registry.gitlab.com/gitlab-org/release-cli:latest
  rules:
    - if: $CI_COMMIT_TAG =~ /^v\d+/
  script: echo "Creating release $CI_COMMIT_TAG"
  release:
    tag_name: $CI_COMMIT_TAG
    description: "Release $CI_COMMIT_TAG of components repository $CI_PROJECT_PATH"

After committing and pushing changes, the pipeline tests the component, then releases it if the test passes.

Convert a CI/CD template to a component

Any existing CI/CD template that you use in projects by using the include: syntax can be converted to a CI/CD component:

  1. Decide if you want the component to be part of an existing components repository to be grouped with other components, or create and set up a new components repository.
  2. Create a YAML file in the components repository according to the expected directory structure.
  3. Copy the content of the original template YAML file into the new component YAML file.
  4. Refactor the new component’s configuration to:
  5. Leverage the .gitlab-ci.yml in the components repository to test changes to the component.
  6. Tag and release the component.