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GitLab CI/CD Cheatsheet

A comprehensive cheat sheet for GitLab CI/CD, covering essential concepts, syntax, and best practices for automating your software development pipeline.

GitLab CI/CD Basics

Core Concepts

CI/CD: Continuous Integration and Continuous Delivery/Deployment. Automates the software development lifecycle.

GitLab CI/CD: Integrated CI/CD tool within GitLab for building, testing, and deploying code.

.gitlab-ci.yml: Configuration file defining the CI/CD pipeline. Located in the root of your repository.

Pipeline: A set of stages and jobs defining the CI/CD process.

Stage: A logical division within a pipeline. Stages run sequentially.

Job: An individual task within a stage. Jobs run in parallel within a stage.

Runner: Executes the jobs defined in the .gitlab-ci.yml file. Can be shared or specific to a project/group.

Artifacts: Files or directories generated by a job that can be used by subsequent jobs or downloaded.

.gitlab-ci.yml Structure 

stages:
  - build
  - test
  - deploy

build_job:
  stage: build
  script:
    - echo "Building..."
    - ./build_script.sh

test_job:
  stage: test
  script:
    - echo "Testing..."
    - ./test_script.sh

deploy_job:
  stage: deploy
  script:
    - echo "Deploying..."
    - ./deploy_script.sh

Key Directives

stages

Defines the stages of the pipeline (e.g., build, test, deploy).

image

Specifies the Docker image to use for the job.

script

Commands to execute within the job.

stage

Assigns the job to a specific stage.

only/except

Controls when a job runs based on branch, tags, etc.

variables

Defines environment variables for the job.

Advanced Configuration

Variables

Define variables in .gitlab-ci.yml:

 
variables:
  MAVEN_CLI_OPTS: "-s .m2/settings.xml --batch-mode"

Precedence (highest to lowest):

CI/CD variables -> Project variables -> Group variables -> Instance variables

Masked variables:

Sensitive variables can be masked in the GitLab UI to prevent them from being printed in job logs.

Artifacts 

job_name:
  stage: ...
  script: ...
  artifacts:
    paths:
      - path/to/artifact1
      - path/to/artifact2
    expire_in: 1 week

paths - Specifies the files/directories to store as artifacts.

expire_in - Sets the expiration time for the artifacts.

Artifacts can be downloaded or passed to subsequent jobs.

Caching 

cache:
  key: "$CI_COMMIT_REF_SLUG"
  paths:
    - .m2/repository

key - A unique key for the cache. Using $CI_COMMIT_REF_SLUG caches per branch.

paths - Specifies the directories to cache.

Caching can significantly speed up build times by reusing dependencies and build outputs.

Conditional Execution & Triggers

Only/Except

only

Run job only for specified refs (branches, tags).

except

Run job for all refs except specified ones.

Example:

 
job_name:
  stage: ...
  script: ...
  only:
    - main
    - tags

Rules

More flexible conditional execution based on various conditions.

 
job_name:
  stage: ...
  script: ...
  rules:
    - if: '$CI_PIPELINE_SOURCE == "merge_request_event"'
      when: always
    - when: never

if - Specifies the condition.

when - Specifies when to run the job (always, on_success, on_failure, manual, delayed, never).

Pipeline Triggers

Trigger pipelines from other pipelines or external sources.

 
trigger_job:
  stage: deploy
  trigger:
    project: group/project
    branch: main

Use trigger: to specify the project and branch to trigger.

Best Practices & Tips

Security

Use masked variables for sensitive information (passwords, API keys).

Avoid storing secrets directly in .gitlab-ci.yml.

Regularly audit your CI/CD configuration.

Use GitLab’s security scanning tools to identify vulnerabilities in your code and dependencies.

Performance

Use caching to reduce build times.

Optimize your Docker images for size and performance.

Run jobs in parallel whenever possible.

Use GitLab Runner autoscaling to dynamically scale your runner infrastructure based on demand.

Maintainability

Keep your .gitlab-ci.yml file organized and well-documented.

Use templates to reuse common CI/CD configurations across multiple projects.

Regularly update your CI/CD configuration to take advantage of new features and improvements.

Test your CI/CD pipeline thoroughly to ensure it is working as expected.
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