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GitLab CI/CD

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By komidawi
4 min read
GitLab CI/CD
  1. docs.gitlab.com/ee/ci/examples
    • CI/CD Templates
    • Example projects
  2. docs.gitlab.com/ee/ci/yaml
    • YAML Syntax Reference
  3. learnxinyminutes.com/docs/yaml
    • YAML Cheatsheet

Knowledge

  1. Pipeline
    • Pipeline is what you’re defining in the .gitlab-ci.yml file, and is what happens when the contents of the file are run on a runner.
    • A pipeline consists of Jobs and Stages
    • Creating a Git tag or adding a Pipeline schedule, do not trigger Pipelines unless you add rules for those cases
  2. Stage
    • Defines order of execution
    • Typical stages are build, test, deploy
    • If there are runners available, jobs in a single stage run in parallel
  3. Job
    • Job specifies tasks for each stage
    • Example Jobs are compile or unit test and integration test
    • Each Job belongs to a Stage
  4. Variables
    1. Scopes
      • project
      • group
      • instance
    2. Types
      1. Predefined Variables
        • Set by GitLab, they provide info about current job, pipeline, environment
        • Usually prefixed with $CI_
      2. Custom Variables
        • Created and managed in GitLab UI, API, or in configuration files
    3. Visibility modifiers
      1. Protected
        • Only available to jobs running on protected branches or tags
      2. Masked
        • Values are hidden in job logs
  5. CI/CD Component
    • Reusable pipeline configuration unit
    • Use a CI/CD Component to compose an entire pipeline configuration or a small part of a larger pipeline
    • You can add a component to your pipeline configuration with include:component
  6. script
    • Each command executes as if it was run as a CLI command.
    • By default, if a command fails or returns an error, the job is flagged as failed and no more commands run.
  7. artifacts
    • If you want files generated in one job to be used in another job, save them as artifacts.
    • Example config:
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        artifacts:
  paths:
    - "build/"
  8. stages
    • stages lists Stages and their order
    • Jobs in the same Stage can run in parallel
    • Jobs in later Stages wait for jobs in earlier Stages to complete
    • If a Job fails, the whole Stage is considered failed and Jobs in later Stages do not start
  9. allow_failure
    • Jobs which fail won’t stop the whole Pipeline
  10. dependencies
    • Use to fetch Artifacts from other Jobs
    • Set dependencies: [] to speed up Job by not fetching Artifacts
  11. Hidden Jobs
    • Jobs that start with dot . are never added to Pipeline
    • Useful for common configurations
  12. extends
    • Used to apply configuration
    • Mostly used to apply Hidden Jobs
  13. default
    • Sets keyword defaults when given configuration not defined in Job
    • E.g. in default: image: ruby:3.0 the image will be set to ruby:3.0 for all Jobs without defined image
    • Otherwise image will be overridden with image specified in Job
  14. Some tips
    • You can validate .gitlab-ci.yml file on GitLab
      • There’s also available JSON Schema
    • Use needs to make dependencies
    • Use rules to add conditions
    • Use cache and artifacts to persist files
    • Use default to add configuration for all jobs
      • Often used to define before_script and after_script
    • Use extends and default to avoid duplication

YAML Features

  1. Anchor &
    • Used to duplicate content across document (duplicate or inherit properties)
    • Valid only in files where defined
    • Use Anchors with Hidden Jobs to provide templates for Jobs
    • In case of duplicated keys, the latest included one key wins (overriding previous ones)
    • Example: .job_template &job_configuration
  2. Merging <<
    • Pastes referenced content
    • Example: <<: *job_configuration
  3. Including Anchor *

Anchor used to build arrays with multiple components

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.default_scripts: &default_scripts
    - ./default-script1.sh
    - ./default-script2.sh

job1:
    script:
        - *default_scripts
        - ./job-script.sh

Anchor with merging

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  .job_template: &job_configuration
  image: ruby:2.6
  services:
      - postgres
      - redis

  test1:
      <<: *job_configuration
      script:
          - test1 project

  test2:
      <<: *job_configuration
      script:
          - test2 project

Anchors for scripts

You can use YAML Anchors with script, before_script, and after_script to use predefined commands in multiple jobs

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.some-script-before: &some-script-before
    - echo "Execute this script first"

.some-script: &some-script
    - echo "Execute this script second"
    - echo "Execute this script too"

.some-script-after: &some-script-after
    - echo "Execute this script last"

job1:
    before_script:
        - *some-script-before
    script:
        - *some-script
        - echo "Execute something, for this job only"
    after_script:
        - *some-script-after

job2:
    script:
        - *some-script-before
        - *some-script
        - echo "Execute something else, for this job only"
        - *some-script-after

Configurations

Maven config

  • Environment variables make Maven use repository homedir instead of the user home for config and dependencies
  • .m2/repository folder is where all the Maven files are stored
  • target folder is where application is created
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variables:
    MAVEN_CLI_OPTS: "-s .m2/settings.xml --batch-mode"
    MAVEN_OPTS: "-Dmaven.repo.local=.m2/repository"

cache:
    paths:
        - .m2/repository/
        - target/
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